WO2015140581A1

WO2015140581A1 - Wound dressing and compositions therefor

Info

Publication number: WO2015140581A1
Application number: PCT/GB2015/050856
Authority: WO
Inventors: Steven L. Percival; Simon FINNEGAN; Stephen Rimmer
Original assignee: Scapa Uk Limited
Priority date: 2014-03-21
Filing date: 2015-03-23
Publication date: 2015-09-24
Also published as: GB201405066D0

Abstract

The present invention relates to medical articles, such as wound dressings, and in particular to the use of compositions comprising a mixture of an amphiphilic co-polymer and a silicone matrix material in the formation of wound contact surfaces for wound dressings. The amphiphilic co-polymer allows a hydrophilic agent, such as a hydrophilic antimicrobial agent, to be loaded into and encapsulated within particles/micelles of the amphiphilic co-polymer, so that the hydrophilic agent can be delivered over time to a wound site when the wound contact surface of a wound dressing, which contains the agent-encapsulated particulate composition, is in contact with the wound. As such, wound infections can be readily treated by hydrophilic agents which would otherwise not be deliverable from the wound contact surface itself.

Description

WOUND DRESSING AND COMPOSITIONS THEREFOR

INTRODUCTION

[0001 ] The present invention relates to an amphiphilic co-polymer, in particular an amphiphilic co-polymer which can be used within wound dressings to capture and retain hydrophilic antimicrobial agents before ultimately delivering said agents to a wound site. The invention also relates to a process for the preparation of the amphiphilic co-polymer, a particulate composition comprising particles of the amphiphilic co-polymer, a process for preparing said particulate composition, an agent-loaded particulate composition said particles; a process for preparing said agent-loaded particulate composition, a silicone- based composition, a process for preparing said silicone-based composition, a medical article, a process for preparing said medical article, a wound dressing, a process for preparing said wound dressing, a kit of parts, and uses of the amphiphilic co-polymer and its derivative compositions for delivering a hydrophilic agent (e.g. an antimicrobial agent) to a wound that is infected, suspected to be infected, or at risk of being infected.

BACKGROUND

[0002] Wound dressings are widely used to promote wound healing and prevent further harm or agitation of the wound. In particular, wound dressings can serve to stem bleeding (and thereby accelerate clotting), absorb wound fluids (such as excess blood, plasma, etc.) and foreign bodies, alleviate pain, mitigate against infection or physical agitation of the wound, expedite granulation and epitheliaization in the healing process, and mask the appearance of the wound and thereby reduce psychological effects.

[0003] Wound dressings, which are typically designed for direct contact with a wound, and often consist of piece of sheet material, such as an absorbent gauze (optionally impregnated with agents to assist sterilization and healing of a wound). Many wound dressings are coated with a non-adhesive or reduced-adhesion wound contact layer to inhibit any adhesion to the wound itself which could otherwise lead to wound trauma and irritation, especially upon removal of the dressing. Slicone-based film layers are now especially popular for use on the wound contact surface of wound dressings (e.g. "soft silicone dressings"). The particular type of silicone can be varied (e.g. from oils to relatively hard rubbers or resins) depending on the clinical need. Such silicone-based films provide a substantially non-adhesive, non- absorbent wound contact layer which is sufficiently permeable to allow wound fluids and foreign bodies to be successfully absorbed by absorbent components (within the dressing) underlying the wound contact layer without the wound dressing undesirably adhering to the wound. It is now generally accepted that patients whose wounds are dressed with silicone-based dressings experience less trauma and less discomfort (especially upon removal of said dessings) than those dressed with other types of dressing.

[0004] Infected wounds are often treated by applying, to a wound, a wound dressing pre-impregnated with an appropriate antiseptic or antimicrobial agent. Alternatively, infected wounds may be treated by applying an antisceptic or antimicrobial agent (e.g. an antiseptic cream or ointment) to the wound prior to the application of a wound dressing. However, the release profile of antimicrobial agents from pre-impregnated wound dressings are often inadequate or non-ideal for treating infected wounds, whilst applying antimicrobial agents to a wound prior to a wound dressing can often lead discomfort and pain or to wound dressings becoming undesirably stuck to the wound, which in turn leads to wound trauma and irritation, especially when the wound dressing is ultimately removed.

[0005] It is an object of the invention to provide materials which enable the manufacture of wound dressings which effectively deliver antimicrobial agents to infected wounds whilst avoiding the shortcomings of the prior art.

SUMMARY OF THE INVENTION

[0006] According to a first aspect of the present invention there is provided an amphiphilic co-polymer comprising:

a silicone polymer backbone Pi comprising a chain of polymerised monomer units Mi' derived or derivable from a monomer Mi , wherein by itself (i.e. not as part of a amphiphilic co-polymer or otherwise functionalised) polymer Pi is (substantially) insoluble in water; and

one or more hydrophilic polymer chains P₂, each comprising a chain of polymerised monomer units M₂' derived or derivable from a monomer M₂, attached to the silicone polymer backbone Pi , wherein by itself (i.e. not as part of an amphiphilic co-polymer or otherwise functionalised) polymer P₂ is (substantially) soluble in water;

wherein each hydrophilic polymer chain P₂ is attached to the silicone polymer backbone Pi (suitably the terminal polymerised monomer unit Mi' thereof) via a linker group L' at a grafting site of Formula la and/or Formula lb:

Formula la

wherein Mi' is a polymerised form of monomer Mi (i.e. the form of monomer Mi when incorporated within a polymer), and L' is a post-graft linker group (i.e. derived from a pre-graft linker group L);

wherein Mi is selected from monomers of the formula M1 or a synthetic equivalent thereof (e.g. a cyclic siloxane):

Formula M1

and each polymerised monomer unit Mi' is selected from polymerised monomer units of formula M1 ':

Formula M1 ' wherein:

Ri and R₂ are each independently selected from:

- (1 -8C)alkyl, aryl, aryl(1 -3C)alkyl, (3-7C)cycloalkyl, optionally substituted by one or more groups selected from vinyl, hydroxy, or amino; or

- hydroxy, amino, vinyl, or allyl,

LGi and LG₂ are each independently a leaving group (e.g. chloro, hydroxyl, -O-

SiRi R₂(LGi)) or substitutable group; n is an integer with a value of 2 or more.

[0007] According to a further aspect of the present invention there is provided a process for the preparation of an amphiphilic co-polymer, the process comprising:

a) providing a silicone polymer backbone Pi comprising a chain of polymerised monomer units Mi' derived or derivable from a monomer Mi , wherein by itself polymer Pi is (substantially) insoluble in water;

Formula M1

and the polymerised monomer unit Mi' is selected from polymerised monomer formula M1 ':

Formula M1 '

wherein:

Ri and R₂ are each independently selected from:

- hydroxy, amino, vinyl, or allyl;

LGi and LG₂ are each independently a leaving group (e.g. chloro, hydroxyl, -O- SiRi R₂(LGi)) or substitutable group;

n is an integer with a value of 2 or more.

b) preparing a functionalised silicone polymer (Pi-L) by functionalising one or more polymerised monomer units Mi' of the silicon polymer backbone Pi to install thereupon one or more pre-graft linker groups L (suitably at the terminal polymerised monomer unit Mi') to provide within the polymer Pi one or more grafting sites of Formula 2a or Formula 2b;

Formula 2a

c) polymerising a monomer M₂ in the presence of the functionalised silicone polymer (Pi-L) to grow (or attach), from the one or more pre-graft linker group(s) L thereof, one or more hydrophilic polymer chains P2 (suitably at the terminal monomer unit Mi' thereof) to produce an amphiphilic co-polymer having one or more grafting sites of Formula la and/or Formula lb:

Formula la

wherein L' is a post-graft linker group derived from the pre-graft linker group L;

wherein by itself polymer P₂ is (substantially) soluble in water.

[0008] According to a further aspect of the present invention there is provided an amphiphilic co-polymer obtainable by, obtained by, or directly obtained by a process for the preparation of an amphiphilic co-polymer as defined herein.

[0009] According to a further aspect of the present invention, there is provided a particulate composition comprising particles of an amphiphilic co-polymer as defined herein, optionally dispersed in a hydrophobic solvent (suitably a hydrophobic solvent that is substantially immiscible with water).

[0010] According to a further aspect of the present invention, there is provided a process for the preparation of a particulate composition, the process comprising contacting an amphiphilic copolymer as defined herein with (or forming an amphiphilic copolymer as defined herein within) a hydrophobic solvent, and optionally thereafter removing some or all of said hydrophobic solvent. [0011 ] According to a further aspect of the present invention, there is provided a particulate composition obtainable by, obtained by, or directly obtained by a process for the preparation of a particulate composition as defined herein.

[0012] According to a further aspect of the present invention, there is provided an agent-loaded particulate composition, comprising particles of an amphiphilic copolymer as defined herein, a hydrophilic agent, and optionally a hydrophobic solvent and/or a hydrophilic solvent.

[0013] According to a further aspect of the present invention, there is provided a process for the preparation of an agent-loaded particulate composition, the process comprising contacting a particulate composition as defined herein with a hydrophilic agent, optionally in the presence of a hydrophilic solvent (suitably a hydrophilic solvent that is substantially miscible with water, most suitably water itself).

[0014] According to a further aspect of the present invention, there is provided an agent-loaded particulate composition obtainably by, obtained by, or directly obtained by a process for the preparation of an agent-loaded particulate composition as defined herein.

[0015] According to a further aspect of the present invention, there is provided a silicone-based composition, comprising a silicone matrix material, an amphiphilic copolymer as defined herein, and optionally a hydrophilic agent (optionally provided in conjunction with the amphiphilic co-polymer as part of an agent-loaded particulate composition as defined herein).

[0016] According to a further aspect of the present invention, there is provided a process for the preparation of a silicone-based composition, the process comprising mixing a silicone matrix material together with either an amphiphilic co-polymer (optionally also with a hydrophilic agent) or an agent-loaded particulate composition as defined herein.

[0017] According to a further aspect of the present invention, there is provided a silicone-based composition obtainable by, obtained by, or directly obtained by a process for the preparation of a silicone-based composition as defined herein.

[0018] According to a further aspect of the present invention, there is provided a medical article (suitably for contact with skin and/or a wound), comprising an amphiphilic co-polymer as defined herein, a particulate composition as defined herein (optionally dried and/or cured), an agent-loaded particulate composition as defined herein, or a silicone- based composition as defined herein.

[0019] According to a further aspect of the present invention, there is provided a process for the preparation of a medical article, the process comprising incorporating within a medical article an amphiphilic co-polymer as defined herein, a particulate composition as defined herein (optionally dried and/or cured), an agent-loaded particulate composition as defined herein, or a silicone-based composition as defined herein, and optionally thereafter contacting said medical article with a hydrophilic agent.

[0020] According to a further aspect of the present invention, there is provided a medical article obtainable by, obtained by, or directly obtained by a process for the preparation of a medical article as defined herein.

[0021 ] According to a further aspect of the present invention, there is provided a wound dressing, comprising an amphiphilic co-polymer as defined herein, a particulate composition as defined herein (optionally dried and/or cured), an agent-loaded particulate composition as defined herein, or a silicone-based composition as defined herein.

[0022] According to a further aspect of the present invention, there is provided a process for the preparation of a wound dressing, the process comprising incorporating within a wound dressing (e.g. by coating an outer surface of a wound dressing or partially assembled wound dressing, suitably an outer surface intended for contact with skin or a wound) an amphiphilic co-polymer as defined herein, a particulate composition as defined herein (optionally dried and/or cured), an agent-loaded particulate composition as defined herein, or a silicone-based composition as defined herein, and optionally thereafter contacting said wound dressing (e.g. the outer surface thereof) with a hydrophilic agent.

[0023] According to a further aspect of the present invention, there is provided a wound dressing obtainable by, obtained by, or directly obtained by a process for the preparation of a wound dressing as defined herein.

[0024] According to a further aspect of the present invention, there is provided a kit of parts comprising a medical article or a wound dressing as defined herein, and a hydrophilic agent.

[0025] According to a further aspect of the present invention, there is provided a use of an amphiphilic co-polymer as defined herein, a particulate composition as defined herein, an agent-loaded particulate composition as defined herein, or a silicone-based composition as defined herein, for delivering a hydrophilic agent (e.g. an antimicrobial agent) to a wound that is infected, suspected to be infected, or at risk of being infected.

[0026] According to a further aspect of the present invention, there is provided an amphiphilic co-polymer as defined herein, a particulate composition as defined herein, an agent-loaded particulate composition as defined herein, or a silicone-based composition as defined herein, for use in treating a wound infection. [0027] Any features, including optional, suitable, and preferred features, described in relation to any particular aspect of the invention may also be features, including optional, suitable and preferred features, of any other aspect of the present invention.

BRIEF DESCRIPTION OF THE DRA WINGS

[0028] For a better understanding of the invention, and to show how embodiments of the same are put into effect, reference is now made, by way of example, to the following diagrammatic drawings, in which:

[0029] Figure 1 shows a SEC chromatograph of (a): allyl-functionalised silicone polymer, with increasing size from left to right; and (b): vinyl-functionalised silicone polymer, again with increasing size from left to right.

[0030] Figure 2 shows low (a), medium (b), and high (c) molecular weight according to above FIG. 1 and Table 1 . Peak colours; dark grey: 1 ^st deconvoluted peak, light grey: 2^nd deconvolved peak, black: raw data.

[0031 ] Figure 3 shows ¹ H NMR of HMCTS showing the integral peaks of H₂0 and CH₃ of HMCTS. Upon comparison of the ratio of integrals of the peaks gave a water percentage content of the material, (a): Before drying, 10% H₂0, (b): After 24hrs of drying, 4% H₂0.

[0032] Figure 4 shows ¹ H NMR of the a functionalised PDMS macromonomer

[0033] Figure 5 shows ¹ H NMR of PDMS macromonomer percentage functionality of both vinyl and ally PDMS macromonomer was calculated using the intergral of the peaks indicated.

[0034] Figure 6 shows the MALDI-TOF mass spectra of functionalised PDMS macromonomer by Allyl Chloroformate.

[0035] Figure 7 shows the ATR-FTIR traces for the Low Mw PDMS co-polymer (1 a from Table 3), Medium Mw PDMS co-polymer (2a from Table 3) and High Mw PDMS copolymer (3a from Table 3).

[0036] Figure 8 shows a typical ¹ H NMR spectrum for a graft coploymer. The broad peaks present are indicative of poly N-vinylpyrrolidone.

[0037] Figure 9 shows the ATR-FTIR spectrum for the Low Mw PDMS co-polymers (1 a-c from Table 3). [0038] Figure 10 shows a comparison between the change in absorption between PDMS macromonomer and PDMS-NVP-graft copolymer 1 a.

[0039] Figure 1 1 shows the ATR-FTIR spectrum for the Low Mw PDMS co-polymers (2a-c from Table 3).

[0040] Figure 12 shows a comparison between the change in absorption between PDMS macromonomer and PDMS-NVP-graft copolymer 2a.

[0041 ] Figure 13 shows the ATR-FTIR spectrum for the Low Mw PDMS co-polymers (3a-c from Table 3).

[0042] Figure 14 shows a comparison between the change in absorption between PDMS macromonomer and PDMS-NVP-graft copolymer 3a.

[0043] Figure 15 shows the normal phase chromatogram of Low MW PDMS 1 a-1 c showing the retention time (minutes) against response in mV. With the references shown in black (PVP) and grey (PDMS macromonomer).

[0044] Figure 16 shows the reverse phase chromatogram of Low MW PDMS 1 a-1 c showing the retention time (minutes) against response in mV. With the references shown in black (PVP) and grey (PDMS macromonomer).

[0045] Figure 17 shows the TGA (thermogravimetric analysis) of a typical copolymer sample showing %weight loss over an increasing temperature range at a rate of 10 degrees per minute

[0046] Figure 18 shows a DSC of a LowM_w1 a showing (a) the first heating cycle in red and cooling shown in blue, (b) is the second heating cycle again shown in red with only one T_g being present.

[0047] Figure 19 shows the DSC for each copolymer sample set showing the trend between samples of roughly the same weight differing in PDMS NVP molar ratios and between sets of varying PDMS macromonomer size.

[0048] Figure 20 shows the particle size analysis of copolymer library micelles in aqueous solution.

[0049] Figure 21 shows the particle size analysis of copolymer library micelles in an organic solvent.

[0050] Figure 22 shows the TEM images of graft copolymers stained with ruthenium, for a) Low Mw PDMS co-polymer (1 a from Table 3) b) Medium Mw PDMS co-polymer (2a from Table 3) and c) High Mw PDMS co-polymer (3a from Table 3). [0051 ] Figure 23 shows enlarged areas of the TEM images showing micelle micro structure for a) Low Mw PDMS co-polymer (1 a from Table 3) b) Medium Mw PDMS copolymer (2a from Table 3) and c) High Mw PDMS co-polymer (3a from Table 3).

[0052] Figure 24 shows light microscope pictures taken for the Low Mw PDMS co- polymer (1 a from Table 3) at 0, 4, 8, 24 and 48hrs at 10, 20 and 40x magnification to determine stability and/or changes in physical morphologies of these apparent swollen micelles.

[0053] Figure 25 shows light microscope pictures taken for the Medium Mw PDMS co-polymer (2a from Table 3) at 0, 4, 8, 24 and 48hrs at 10, 20 and 40x magnification to determine stability and/or changes in physical morphologies of these apparent swollen micelles.

[0054] Figure 26 shows light microscope pictures taken for the High Mw PDMS copolymer (3a from Table 3) at 0, 4, 8, 24 and 48hrs at 10, 20 and 40x magnification to determine stability and/or changes in physical morphologies of these apparent swollen micelles.

[0055] Figure 27 shows SEM images of three different membranes, where the membranes respectively contained 0, 1 and 10% copolymer (i.e. the weight ratio of copolymer to PDMS matrix material was 0, 1 :100 and 1 :10 respectively), shown from left to right.

[0056] Figure 28 shows SEM images following a peel test. The peel test was conducted simply by taking the 'stub' used for SEM imaging to which the SEM imaging is typically done, and imprinting this onto the membrane.

[0057] Figure 29 shows confocal images of three membranes all Z stacked using LSM image browser, (a); 0.1 % copolymer with elongated spheres roughly ranging from 5-15μηι in length and 5μηι in width, (b); 1% copolymer showing large elongated spheres showing a large range of sizes from 5 up to 50μηι. (c); 10% copolymer showing a diffuse layer of copolymer and rhodamine B throughout the entire membrane.

[0058] Figure 30 shows the confocal images for copolymer (Low MW PDMS 1 a) containing fluorescein o-acrylate dissolved in H₂0 at 5mg/ml concentration, wherein in the top left the confocal image for just fluorescein o-acrylate is displayed, in the top right the confocal image for just Rhodamine B is displayed, and at the bottom the overlaid images are displayed.

[0059] Figure 31 shows the confocal images for copolymer (Low MW PDMS 1 a) containing fluorescein o-acrylate dissolved in hexamethyldisolxane at 5mg/ml concentration, wherein in the top left the confocal image for just fluorescein o-acrylate is displayed, in the top right the confocal image for just Rhodamine B is displayed, and at the bottom the overlaid images are displayed.

[0060] Figure 32 is a graph showing the contact angles as a dependency of % copolymer present within the membrane in a) H₂0 and b) 1 -Bromonaphthalene.

[0061 ] Figure 33 shows the peel adhesion results for a) Low Mw PDMS co-polymers (1 a-c from Table 3) b) Medium Mw PDMS co-polymers (2a-c from Table 3) and c) High Mw PDMS co-polymers (3a-c from Table 3). All membranes were 25 mm in width with a peel length of 225 mm and were peeled at a rate of 300 mm/min with a start tension of 0.08 N with polycarbonate being used as the stationary phase. The reference region is shown between the two black dotted lines, this region is peel adhesions conducted under the same conditions but with silicone only gels made under the typical industry conditions (120 °C) and the conditions used to make the doped silicone gels (70 °C).

[0062] Figure 34 shows the gnr²24hr¹ of water loss for a) Low Mw PDMS co-polymers (1 a-c from Table 3) b) Medium Mw PDMS co-polymers (2a-c from Table 3) and c) High Mw PDMS co-polymers (3a-c from Table 3).

[0063] Figure 35 shows the release profile of rhodamine B from the membranes at 0, 0.5, 1 .5, 4, 24, 48hr time periods ranging from 0.1 % to 10% copolymer concentrations, as measured using a specord S600 spectroscope with the wavelength of 500 - 600nm. The following lines correspond with the following measurement times Black; Ohr (solid), 0.5hr (lines), 1 .5hr (dotted), Grey; 4hr (solid), 24hr (lines), 48hr (dotted).

[0064] Figure 36 shows the 7 day release profiles of 0.1 , 0.5, 1 , 2.5, 5 and 10% copolymer (with the Rhodamine/copolymer ratios corresponding to those of Table 8) showing the general trend that as the amount of Rhodamine B is increased within the copolymer present in the membrane, the larger the absorption observed after 7 days.

[0065] Figure 37 shows the 72 hour time point release profiles of 0.1 to 10 % membranes with scans taken at 551 nm at time intervals of 30 min for the first 4 hr and then every hour until 12 hr. he remaining time points were taken at 16, 24, 36, 48, 60 and 72 hr.

[0066] Figure 38 shows the fraction of Rhodamine B released against time below 60% of maximum release to obtain power exponent 'η' of 0.1 -5% copolymer composition, as tabulated in Table 12.

[0067] Figure 39 shows the Rhodamine release for all copolymer compositions (1 a- 3c) monitored over 48hs and at various concentrations (0.1 , 0.5, 1 , 2.5 and 5%). [0068] Figure 40 shows the calculated Fickian constant of all copolymer compositions (1 a-3c) at five increasing concentrations of Rhodamine B (0.1 , 0.5, 1 , 2.5 and 5%).

[0069] Figure 41 shows the silver release data for all membranes, loaded at a 1 % Ag concentration. Release was monitored via a gravimetric method with low PDMS MW 1 a, Medium PDMS MW 2a and High MW PDMS 3c releasing the maximum amount of Ag over a five day period.

[0070] Figure 42 shows the silver release data for all membranes, loaded at a 2.5% Ag concentration. Release was monitored via a gravimetric method with low PDMS MW 1 a, eleasing the maximum amount of Ag over a five day period.

[0071 ] Figure 43 shows the four measurements taken (A, B, C and D) in the corrected zone inhibition studies.

[0072] Figure 44 shows the corrected zone inhibition studies for the polymer composition low MW PDMS 1 a for a) 2.5% copolymer (1 a) and 1 % Ag Staphylococcus b) 2.5% copolymer (1 a) and no Ag Staphylococcus c) 2.5% copolymer (1 a) and 1 % Ag Pseudomonas and d) 2.5% copolymer (1 a) and no Ag Pseudomonas.

[0073] Figure 45 shows the corrected zone inhibition studies for the polymer composition medium MW PDMS 2a for a) 2.5% copolymer (2a) and 1 % Ag Staphylococcus b) 2.5% copolymer (2a) and no Ag Staphylococcus c) 2.5% copolymer (2a) and 1 % Ag Pseudomonas and d) 2.5% copolymer (2a) and no Ag Pseudomonas.

[0074] Figure 46 shows the corrected zone inhibition studies for the polymer composition high MW PDMS 3c for a) 2.5% copolymer (3c) and 1 % Ag Staphylococcus b) 2.5% copolymer (3c) and no Ag Staphylococcus c) 2.5% copolymer (3c) and 1 % Ag Pseudomonas and d) 2.5% copolymer (3c) and no Ag Pseudomonas.

[0075] Figure 47 shows the corrected zone inhibition studies for the control experiment, wherein no polymer composition was added. Shown are the corrected zone inhibition traces for a) 1 % Ag no graft copolymer Staphylococcus b) 1 % Ag + H₂0 no graft copolymer Staphylococcus c) 1 % Ag no graft copolymer Pseudomonas and d) 1 % Ag + H₂0 no graft copolymer Pseudomonas.

[0076] Figure 48 shows the initial inoculation of bacteria on the left in black and control adjacent to this in white with the test materials also shown. All materials were tested against both S. aureus and P. aeruginosa.

[0077] Figure 49 shows the comparision of % of cell survival of treated cells to untreated positive growth in direct contact, calculated using alamar blue assay. [0078] Figure 50 shows the comparision of % of cell survival of treated cells to untreated positive growth in indirect contact, calculated using alamar blue assay.

[0079] Figure 51 shows the comparison of the number of cells to untreated positive growth in direct contact, calculated using Picogreen assay.

[0080] Figure 52 shows the comparison of the number of cells to untreated positive growth in indirect contact, calculated using Picogreen assay.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

[0081 ] Unless otherwise stated, the following terms used in the specification and claims have the following meanings set out below.

[0082] Herein, the term "hyd rophilic solvent" means a solvent (or mixture of solvents) which is substantially miscible with water.

[0083] Herein, the term "hydrophobic solvent" means a solvent (or mixture of solvents) which is substantially immiscible with water.

[0084] It is to be appreciated that references to "treating" or "treatment" include prophylaxis as well as the alleviation of established symptoms of a condition. "Treating" or "treatment" of a state, disorder or condition therefore includes: (1 ) preventing or delaying the appearance of clinical symptoms of the state, disorder or condition developing in a human that may be afflicted with or predisposed to the state, disorder or condition but does not yet experience or display clinical or subclinical symptoms of the state, disorder or condition, (2) inhibiting the state, disorder or condition, i.e., arresting, reducing or delaying the development of the disease or a relapse thereof (in case of maintenance treatment) or at least one clinical or subclinical symptom thereof, or (3) relieving or attenuating the disease, i.e., causing regression of the state, disorder or condition or at least one of its clinical or subclinical symptoms.

[0085] A "therapeutically effective amount" means the amount of a compound or agent (e.g. hydrophilic agent such as an antimicrobial agent) that, when administered to a mammal for treating a disease, is sufficient to effect such treatment for the disease or condition. The "therapeutically effective amount" will vary depending on the compound, the disease or condition and its severity and the age, weight, etc., of the mammal to be treated. [0086] In this specification the term "alkyi" includes both straight and branched chain alkyi groups. References to individual alkyi groups such as "propyl" are specific for the straight chain version only and references to individual branched chain alkyi groups such as "isopropyl" are specific for the branched chain version only. For example, "(1 -6C)alkyl" includes (1 -4C)alkyl, (1 -3C)alkyl, propyl, isopropyl and f-butyl. A similar convention applies to other radicals, for example "phenyl(1 -6C)alkyl" includes phenyl(1 -4C)alkyl, benzyl, 1 -phenylethyl and 2-phenylethyl.

[0087] The term "(m-nC)" or "(m-nC) group" used alone or as a prefix, refers to any group having m to n carbon atoms.

[0088] "(3-8C)cycloalkyl" means a hydrocarbon ring containing from 3 to 8 carbon atoms, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl or bicyclo[2.2.1 ]heptyl.

[0089] The term "aryl" means a cyclic or polycyclic aromatic ring having from 5 to 12 carbon atoms. The term aryl includes both monovalent species and divalent species. Examples of aryl groups include, but are not limited to, phenyl, biphenyl, naphthyl and the like. In particular embodiment, an aryl is phenyl.

[0090] The term "aryl(1 -6C)alkyl" means an aryl group covalently attached to a (1 - 6C)alkylene group, both of which are defined herein. Examples of aryl-(1 -6C)alkyl groups include benzyl, phenylethyl, and the like.

[0091 ] The term "monomer" refers to the starting material used to produce a corresponding polymer. As such, a particular polymer Pi may be considered derived or derivable from a monomer Mi where polymerisation of the monomer Mi would yield said polymer. The polymer Pi may also be considered as a chain of polymerised monomer units Mi', where Mi' is the form of monomer Mi once it has been incorporated into a polymer chain. Where monomers are used to define the structural characteristics of a polymer, it will be understood by those skilled in the art that other monomers may also be suitable for forming the same polymer (e.g. with different leaving groups).

[0092] References to solubilities of particular polymeric blocks of a given amphiphilic co-polymer (e.g. the silicone Pi block or hydrophilic P₂ block) suitably refer to the solubility of that particular polymeric block (e.g. whether Pi or P₂) by itself (i.e. without being associated with any of the other blocks of the relevant amphiphilic co-polymer).

[0093] Herein a "grafting site" is the site (or polymerised monomer unit) within a polymer to which another polymer is attached or grafted. A grafting site of a given polymer (e.g. of Pi) typically has either a pre-graft linker group L (e.g. before a second polymer is grafted) or a post-graft linker group L' (i.e. once the second polymer has been grafted). L' is suitably the L pre-graft linker group transformed by the polymerisation reaction - for instance if the pre-graft linker group L comprises a vinyl moiety from which a polymer (e.g. P₂) is suitably grown (e.g. through free-radical polymerisations), the post graft linker group L' will typically be the saturated analogue thereof because the vinyl group will have then reacted.

[0094] Where the quantity or concentration of a particular component of a given composition is specified as a weight percentage (wt% or %w/w), said weight percentage refers to the percentage of said component by weight relative to the total weight of the composition as a whole. It will be understood by those skilled in the art that the sum of weight percentages of all components of a composition will total 100 wt%. However, where not all components are listed (e.g. where compositions are said to "comprise" one or more particular components), the weight percentage balance may optionally be made up to 100 wt% by unspecified ingredients (e.g. a diluent, such as water, or other non-essentially but suitable additives).

[0095] Herein, where a composition is said to "consists essentially of" a particular component, said composition suitably comprises at least 70 wt% of said component, suitably at least 90 wt% thereof, suitably at least 95 wt% thereof, most suitably at least 99 wt% thereof. Suitably, a composition said to "consist essentially of" a particular component consists of said component save for one or more trace impurities.

[0096] The term "molecular weight" may refer to either or both of a mass average molar mass (M_w) or Number average molar mass or (M_n). Most suitably, unqualified references to "molecular weight" refers to M_w. Furthermore, suitably any unqualified references to "molecular weight" in the context of polymers refers to the average molecular weight (given that polymers generally exhibit a distribution of molecular weights).

[0097] Herein, the term "particle size" suitably refers to the length of the longest dimension of a given particle, though diameter may be used for substantially spherical particles. The corresponding term "average particle size" suitably refers to the mean- average particle size of particles in a sample.

[0098] Herein, amounts stipulated for components and ingredients, whether specified in terms of "parts", ppm (parts per million), percentages (%, e.g. wt%), or ratios, are intended to be by weight, unless stated otherwise.

[0099] Herein, unless stated otherwise, the term "parts" (e.g. parts by weight, pbw) when used in relation to multiple ingredients/components, refers to relative ratios between said multiple ingredients/components. Though in many embodiments the amounts of individual components within a composition may be given as a "wt%" value, in alternative embodiments any or all such wt% values may be converted to parts by weight to define a multi-component composition. This is so because the relative ratios between components is often more important than the absolute concentrations thereof in either the fuel additive composition or fuel composition itself. Where a composition comprising multiple ingredients is described in terms of parts by weight alone (i.e. to indicate only relative ratios of ingredients), it is not necessary to stipulate the absolute amounts or concentrations of said ingredients (whether in toto or individually) because the advantages of the invention stem from the relative ratios of the respective ingredients rather than their absolute quantities or concentrations. For instance, the dilution level of an silicone-based composition is usually unimportant, since often said compositions will be dried or cured to some extent in use and, in any case, preprepared compositions merely provide a convenient means to achieve particular concentrations of the stipulated ingredients (in a stipulated relative ratio) within an ultimate product. The actual amount of silicone-based composition to be added to a given product can be judiciously selected based on the concentration of the ingredients within the compositon and the desired final concentration desired within the product.

General Principles and Advantages of the Invention

[00100] The present invention provides silicone-based amphiphilic co-polymers comprising a hydrophobic silicone-based polymeric block and one or more hydrophilic polymer blocks. Such amphiphilic co-polymers advantageously form micelle particles having a hydrophilic core when dispersed in a hydrophobic solvent. This micellular structure allows said particles to efficiency absorb, retain, and encapsulate a hydrophilic agent, such as a hydrophilic antimicrobial agent, within its core when said particles are mixed with a relevant hydrophilic agent.

[00101] Such agent-loaded amphiphilic co-polymer particles are highly compatible for admixing with silicone matrix materials, such as polydimethylsiloxane (PDMS), commonly used on the wound contact surface of wound dressings. Such mixtures of agent-loaded amphiphilic co-polymer and silicone matrix materials retain their hydrophobic character and substantiaoly non-stick character, and thus retain their ability to function as effective wound contact surfaces (e.g. preventing wound trauma through being non-adhesive, whilst also being permeable to wound liquids and foreign nodies), but have the additional advantage that they can release the hydrophilic agent (e.g. antimicrobial) contained therein and deliver it directly to the wound site (since it is in close proximity by virtue of its core function). Such dual functioning silicone-based wound contact surface alleviates the need to either pre-treat wounds with antiseptic cream (which can cause discomfort and lead to the wound becoming adhered to the dressing) or pre-impregnate a wound dressing with an anticeptic (which is non-ideal, especially since such pre-impresnated anticeptics are generally pre-absorbed within the body of the wound dressing away from the wound contact surface, thus compromising its delivery to the wound).

[00102] Thus, the amphiphilic co-polymers of the invention are superior vehicles for carrying hydrophilic antimicrobial agents, and furthermore possess particular physical and chemical characteristics which allow for their inclusion at the contact surface of wound dressings to enable the facile delivery to a wound site of the antimicrobial agents contained therein

Silicone-based Amphiphilic co-polymer

[00103] The present invention provides an amphiphilic co-polymer which comprises a silicone polymer backbone Pi (suitably comprising a chain of polymerised monomer units Mi' derived or derivable from a monomer Mi) attached to which polymer Pi (preferably via a linker) are one or more hydrophilic polymer chains P₂ (suitably each comprising a chain of polymerised monomer units M₂' derived or derivable from a monomer M₂). The skilled person will readily appreciate that whilst specifically defined monomers Mi and M₂ (such as those defined herein by formulas Mi and M₂) may be used to produce their respective polymers Pi and P₂, other synthetic equivalents of said monomers may also be employed to form a chain of polymerised monomer units Μ (i.e. polymer Pi) or a chain of polymerised monomer units M₂' (i.e. polymer P₂). As such, suitably Pi is suitably derivable from (i.e. is obtainable by, or obtained by polymerisation of) monomer(s) Mi (though alternative synthetic equivalents may be used in any actual synthesis to give rise to the same polymer Pi), and/or suitably P₂ is derivable from (i.e. is obtainable by, or obtained by polymerisation of) monomer(s) M₂ (though alternative synthetic equivalents may be used in any actual synthesis to give rise to the same polymer Pi).

[00104] Each hydrophilic polymer chain P₂ is suitably attached to the silicone polymer backbone Pi via a linker group L' at a grafting site of Formula la and/or Formula lb:

Formula la Formula lb

wherein L' is a post-graft linker group (i.e. derived from a pre-graft linker group L).

Silicone polymeric backbone Pi and related monomers Mi

[00105] The silicone polymer backbone Pi , by itself, is (substantially) insoluble in water. Preferably the water-solubility of the Pi is less than or equal to 1 g/L, suitably less than or equal to 0.1 g/L.

[00106] Though silicone polymer backbones Pi may encompass branched and/or cross-linked polymers, in preferred embodiments Pi is (substantially) linear.

[00107] Polymer Pi may be a homopolymer or, in certain circumstances, may be a copolymer (most suitably a random co-polymer). Suitably, where Pi is a co-polymer, the polymer optionally comprises at least some polymerised monomeric units Mi' (suitably silicon-based, suitably derived from a monomer Mi) which are either functionalised (e.g. comprising pre-installed vinyl or allyl or groups) or capable of being functionalised (e.g. thus comprising a functionalisable hydroxy or amino group) to exhibit or produce one or more internal/non-terminal grafting sites (suitably of Formula 2b) in addition to any grafting sites at the terminus of the polymer Pi . Where Pi is a co-polymer, the polymer Pi may comprise two or more different polymerised monomer units Mi' derived from two or more different monomers Mi . Such functionalised or functionalisable co-polymers Pi allows for the formation of graft co-polymer in which one or more P2 polymeric side chains are grafted to internal (non-terminal) grafting sites of the silicone polymeric backbone Pi in addition to any attachment of a P₂ polymer to the terminus of Pi . However, in preferred embodiments, Pi is free of any polymerised monomeric units Mi' which are either functionalised or capable of being functionalised to exhibit or produce one or more grafting sites - suitably the only grafting sites of Pi are terminal grafting sites (i.e. at the terminus of the polymer chains, e.g. a hydroxyl, or oxy anion terminus). In preferred embodiments hydrophilic polymer chain(s) P₂ are (substantially) solely grafted to terminal monomeric units of the silicone polymer backbone Pi , as per Formula la. Most suitably, the silicone polymeric backbone Pi comprises at least 95% of one type/form of polymerised monomeric unit Mi' (derived from a single monomer Mi), suitably at least 97%, suitably at least 99%. In preferred embodiments, the silicone polymeric backbone Pi is a homopolymer comprising a single type/form of polymerised monomeric unit Mi' (derived from a single monomer Mi).

[00108] Mi is suitably selected from monomers of the formula M1 or a synthetic equivalent thereof (e.g. a cyclic siloxane): LG-ι— Si LG₂

Formula M1

and each polymerised monomer unit Mi' is thus suitably selected from polymerised monomer units of formula M1 ':

Formula M1 '

Ri and R₂ are each independently selected from:

- hydroxy, amino, vinyl, or allyl,

[00110] Suitably Ri and/or R₂ only comprise a hydroxy, amino, vinyl, or allyl group where the polymer Pi comprises one or more grafting sites of Formula 1 b or 2b (i.e. to allow for the preparation of a graft co-polymer with one or more P₂ polymeric side chains branching from the silicone polymeric backbone Pi). However, in preferred embodiments, the polymer Pi only comprises grafting site(s) of Formula 1 a, and Ri and R₂ are free of any hydroxy, amino, vinyl, or allyl groups. As such, Ri and R₂ are suitably each independently selected from (1 -8C)alkyl, aryl, aryl(1 -3C)alkyl, (3-7C)cycloalkyl. Suitably Ri and R₂ are each independently selected from (1 -8C)alkyl and aryl. Suitably Ri and R₂ are each independently selected from (1 -4C)alkyl and phenyl. In a particular embodiment, Ri and R₂ are each independently selected from methyl, ethyl, butyl, and phenyl. Though Ri and R₂ may be the same or different, they are suitably the same. In a particular embodiment, both Ri and R₂ are methyl.

[00111] In a particular embodiment, a synthetic equivalent of monomer Mi used to form a polymer Pi comprising a chain of polymerised monomer units Mi' is the compound of formula:

wherein Ri and R₂ are as defined herein (most suitably both Ri and R₂ are methyl)

[00112] In a particular embodiment, the polymer Pi is selected from polydimethylsiloxane (PDMS), polydiethylsiloxane (PDES), polymethylethylsiloxane (PMES), polydiphenylsiloxane (PDPS), and polymethylphenylsiloxane (PMPS). In a particular embodiment, the polymer Pi is polydimethylsiloxane (PDMS).

[00113] Suitably, the terminal group of the silicone polymer backbone Pi (prior to any installation of a linker/grafting moiety) is selected from O , OH, NH₂, NHR, or OR, wherein R is selected from (1 -8C)alkyl, suitably from (1 -4C)alkyl. Suitably, the terminal group of the silicone polymer backbone Pi (prior to any installation of a linker/grafting moiety) is selected from O^" or OH.

[00114] Suitably n is an integer between 6 and 500, suitably between 13 and 300, suitably between 20 and 200. In a particular embodiment, n is an integer between between 24 and 160.

[00115] Suitably the polymer Pi has a molecular weight (M_w) or a molecular weight (Mn) between 500 and 30000 g/mol, suitably between 1000 and 20000 g/mol, suitably between 1500 and 15000 g/mol. In a particular embodiment, the polymer Pi has a molecular weight (Mw) or a molecular weight (M_n) between 1800 and 1 1000 g/mol.

[00116] Suitably the polymer Pi has a polydispersity index (PDI - M_w/M_n) of between 0.8 and 1 .5, more suitably between 0.9 and 1 .3, more suitably between 1 .0 and 1 .2, most suitably between 1 .05 and 1 .15.

[00117] In terms of the monomer Mi , LGi and LG₂ are each independently a leaving group, which may be the same or different. Suitably, LGi and LG₂ are each independently selected from halo (e.g. chloro), hydroxyl, (1 -8C)alkoxy, aryloxy, aryl(1 -8C)alkoxy, another a silyloxy group (e.g. -0-SiRi R₂(LGi)), or LGi and LG₂ are linked so that together with the silicon atom to which they are both attached, they form a ring (e.g. a siloxane ring).

[00118] The silicone polymeric backbone Pi suitably comprises the same polymerised monomeric units (Mi'), derived or derivable from the same monomer Mi , as the silicone matrix material. Suitably both are PDMS polymers (i..e. where Ri and R₂ are both methyl). The silicone polymeric backbone Pi suitably has a molecular weight (M_w) that is between 50 and 150% of that of the silicone matrix material (i.e. the ratio of molecular weights of Pi to silicone matrix material is between 1 :2 and 2:3), suitably between 70 and 130% of the silicone matrix material, suitably between 90 and 1 10% of the silicone matrix material. Most suitably the silicone polymeric backbone Pi has a lower molecular weight (M_w) than that of the silicone matrix material.

Linker

[00119] Where the amphiphilic co-polymer comprises a silicone polymer backbone Pi and one or more hydrophilic polymer chains P2, such that each hydrophilic polymer chain P₂ is attached to the silicone polymer backbone Pi via a linker group L' at a grafting site (suitably at a grafting site of Formula la and/or Formula lb):

Formula la Formula lb

wherein L' is a post-graft linker group;

the post-graft linker group L' is suitably derived from a pre-graft linker group L which changes form to L' when a P₂ chain is reacted therewith or otherwise grafted or attached thereto.

[00120] References to linkers which contain vinyl moieties intended to react with other vinyl moieties during the attachment of P₂ chain(s) to Pi (e.g. with monomers M₂) suitable relate to pre-graft linkers (L), whereas corresponding post-graft linkers (U) will generally lose said vinyl moieties (which are suitably duly transformed into saturated carbon-carbon bonds during the polymerisation process). Unless stated otherwise, unqualified references to a linker group in the context of the amphiphiliic co-polymer relate to the pre- graft linker. The skilled person will readily appreciate the corresponding structure and form of any post-graft linker groups from a definition of any pre-graft linker groups. Most suitably, any post-graft linker groups L' are saturated analogues (suitably linked to a polymer chain P₂) of correspondingly unsaturated pre-graft linker groups L.

[00121] Though, as outlined above, linker groups L' and L may be attached to internal (i.e. non-terminal) grafting sites within the polymer Pi , in preferred embodiments L' and L are only attached to terminal grafting sites of Pi (i.e. at the terminus of the polymer chains, e.g. a hydroxyl, or oxy anion terminus), most suitably to form a grafting site of formula 2a (in the case of a functionalised silicone polymer (Pi-L)) or a grafting site of formula 1 a (in the case of the fully formed amphiphilic co-polymer):

Formula 2a Formula la

[00122] The pre-graft linker group L suitably comprises a vinyl moiety (or other crosslinkable or polymerisable moieties) to which polymer chain(s) P₂ may be attached or from which polymer chain(s) P2 may be grown (e.g. via living radical polymerisation reactions). Suitably, any remaining portions of the linker L are (substantially) inert to polymerisation reactions, especially living radical polymerisation reactions.

[00123] In some embodiments, the linker (L or L') may be an integral part of one or more of the polymerised monomer units Mi' (derived or derivable from a corresponding monomer Mi in which said linker forms an integral part). For instance, where the monomer Mi is a monomer of formula M1 (as defined herein) and the polymerised monomeric units Mi' are of formula M1 ' (as defined herein), the linker (L or L') may be attached directly to the relevant silicon atom (e.g. as a vinyl or allyl pre-graft linker group L to form a vinyl or allyl silane group).

[00124] However, in preferred embodiments, the linker (L or L') is non-intergral to any of the polymerised monomer units Mi', and is instead installed separately (e.g. via the process(es) defined herein) after the polymer Pi has been formed - i.e. the polymer Pi is functionalised to form a functionalised silicone polymer (P1-L), suitably with a grafting site of formula 2a or 2b, most preferably a grafting site of formula 2a. As such, the linker is suitably attached to the polymer Pi via a functionalisable group of the polymerisable monomeric unit Mi' at the grafting site, suitably a nucleophilic functionalisable group, such as a group selected from O , OH, NH₂, NHR (wherein R is selected from (1 -8C)alkyl, suitably from (1 -4C)alkyl). For instance, where the monomer Mi is a monomer of formula M1 (as defined herein) and the polymerised monomeric units Mi' are of formula M1 ' (as defined herein), the linker (L or L') may be attached to the silicon atom via a functionalisable group of the polymerisable monomeric unit Mi' at the grafting site, suitably a nucleophilic functionalisable group, such as a group selected from O , OH, NH₂, NHR (wherein R is selected from (1 -8C)alkyl, suitably from (1 -4C)alkyl). Most suitably, the grafting site is a terminal grafting site. Most suitably the linker (L or L') is attached to a silanol group, most suitably a terminal silanol group (i.e terminal hydroxyl group) or a deprotonated form thereof. Again the pre-graft linker group L suitably comprises a vinyl moiety (or other crosslinkable or polymerisable moieties) to which polymer chain(s) P2 may be attached or from which polymer chain(s) P₂ may be grown (e.g. via living radical polymerisation reactions). Most suitably the linker group L is or comprises a group selected from a (2-8C)alkenyl (e.g. vinyl or allyl), (3-8C)alkenoyl (i.e. ketone with vinyl moiety) or (2-8C)alkenyloxycarbonyl (e.g. vinyloxycarbonyl or allyloxycarbonyl). Suitably In a particular embodiment the linker group L is or comprises a group selected from a (2- 3C)alkenyl (e.g. vinyl or allyl), (3-4C)alkenoyl (i.e. ketone with vinyl moiety) or (2- 3C)alkenyloxycarbonyl (e.g. vinyloxycarbonyl or allyloxycarbonyl). In a particular embodiment, the linker group L is selected from vinyloxycarbonyl or allyloxycarbonyl. In a particular embodiment, the linker group L is allyloxycarbonyl.

[00125] Suitably, the pre-graft linker group L is defined by the formula:

wherein ^* is an atom or group of Pi to which the linker group L is attached, and Ri_ is a vinyl-containing (i.e. alkene-containing) group.

[00126] Suitably R_L is selected from (2-8C)alkenyl (e.g. vinyl or allyl) or (2- 8C)alkenyloxy (e.g. vinyloxy or allyloxy).

[00127] Suitably ^* (the atom of Pi to which the linker group L is attached) is an oxygen (whether derived from oxy, oxide, or hydroxyl).

[00128] Most suitably, said pre-graft linker groups are formed by a reaction between a functionalisable group of the polymer Pi (suitably a polymerisable monomeric unit Mi' at the grafting site), preferably a O^" or OH group, and a reactive (or couplable) form of the linker group L-LGL, where L is the pre-graft linker group, and LGi_ is a leaving group, such as halo (e.g. chloro). In a particular embodiment, the pre-graft linker groups are formed by a reaction between a terminal O^" or OH group of the silicone polymer backbone Pi and either one of vinylchloroformate or allylchloroformate.

[00129] Suitably at least 40% of available grafting sites upon the silicone polymer backbone Pi (i.e. at least 40% of functionalisable groups of Pi) are functionalised with a linker group (and suitably also a P₂ chain in the case of the amphiphilic co-polymer), suitably at least 50%, suitably at least 70%, suitably at least 85%, suitably at least 90%. Suitably at least 40% of available terminal grafting sites upon the silicone polymer backbone Pi (i.e. at least 40% of functionalisable groups of Pi) are functionalised with a linker group (and suitably also a P₂ chain in the case of the amphiphilic co-polymer), suitably at least 50%, suitably at least 70%, suitably at least 85%, suitably at least 90%.

[00130] In a preferred embodiment, the grafting site(s) are defined by the formula 2A (for functionalised silicone polymer P L) or the formula 1 A (for the amphiphilic copolymer):

Formula 2A Formula IA

[00131] In a particular embodiment, the grafting site(s) of formula 2A are selected from:

Formula 2A' Formula IA'

and the grafting site(s) of formula 1 A are selected from:

P2 ihvdrophilic part)

[00132] The hydrophilic polymer P₂, by itself, is (substantially) soluble in water. Preferably the water-solubility of the P₂ is greater than or equal to 2g/L, suitably greater than or equal to 10g/L, suitably greater than or equal to 100g/L. [00133] Suitably the monomer(s) M₂ are (substantially) water-soluble, suitably with a water solubility greater than or equal to 2g/L, suitably greater than or equal to 10g/L, suitably greater than or equal to 50g/L.

[00134] The hydrophilic polymer(s) P₂ may be a homopolymer or, in certain circumstances, may be a co-polymer (most suitably a random co-polymer). Most suitably, the polymer(s) P₂ comprises at least 95% of one type/form of polymerised monomeric unit M₂' (derived from a single monomer M₂), suitably at least 97%, suitably at least 99%. In preferred embodiments, the polymer(s) P₂ is a homopolymer comprising a single type/form of polymerised monomeric unit M₂' (derived from a single monomer M₂).

[00135] M₂ is suitably selected from hydrophilic monomers possessing a vinyl moiety (suitably reactive in free radical polymerisation reactions with other vinyl moieties), suitably a terminal vinyl moiety. M₂ is suitably selected from alkenes substituted with one or more hydrophilic moieties which enable the corresponding polymer P₂ to be water soluble, wherein the hydrophilic moieties are suitably inert to polymerisation reaction conditions, suitably inert to free radical polymerisation reaction conditions.

[00136] In a particular embodiment, the monomer M₂ is selected from N- vinylpyrrolidone (NVP to make PVP chains), N-vinylcapralactam, vinyl acetate, vinyl alcohol, hydrophilic acrylates and acrylic acids (including alkylacrylates and any hydrophilic derivatives), hydrophilic arylamides (including alkylacrylamides and any hydrophilic derivatives), hydrophilic styrenes, and any salts (e.g. hydrochloride, sodium) or acid forms thereof, or any mixture thereof.

[00137] In a particular embodiment, the monomer M₂ is selected from N- vinylpyrrolidone (NVP to make PVP chains), N-vinylcapralactam, vinyl acetate, vinyl alcohol, acrylic acid, 2-aminoethyl methacrylate, methacrylic acid, 4-styrenesulfonic acid, Ν,Ν'-dimethyl acrylamide, glycerol monomethacrylate, potassium 3- sulfopropylmethacrylate, oligo(ethylene glycol) methacrylate, oligo(ethylene glycol) acrylate, 2-(dimethylamino)ethyl methacrylate, 2-(diisopropylamino)ethyl methacrylate, 2- (methacryloyloxy)ethyl phosphorylcholine, 2-Hydroxyethyl acrylate, 2-Hydroxyethyl methacrylate, methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate or methyl iodiide-quaternized 2-(dimethylamino)ethyl methacrylate, 2-(methacryloyloxy)ethyl succinate, and any salts (e.g. hydrochloride, sodium) or acid forms thereof, or any mixture thereof.

[00138] In a particular embodiment, the polymer(s) P₂ is a homopolymer formed by a single monomer selected from N-vinylpyrrolidone (NVP to make PVP chains), N- vinylcapralactam, vinyl acetate, vinyl alcohol, acrylic acid, 2-aminoethyl methacrylate, methacrylic acid, 4-styrenesulfonic acid, Ν,Ν'-dimethyl acrylamide, glycerol monomethacrylate, potassium 3-sulfopropylmethacrylate, oligo(ethylene glycol) methacrylate, oligo(ethylene glycol) acrylate, 2-(dimethylamino)ethyl methacrylate, 2- (diisopropylamino)ethyl methacrylate, 2-(methacryloyloxy)ethyl phosphorylcholine, 2- Hydroxyethyl acrylate, 2-Hydroxyethyl methacrylate, methyl chloride-quaternized 2- (dimethylamino)ethyl methacrylate or methyl iodiide-quaternized 2-(dimethylamino)ethyl methacrylate, 2-(methacryloyloxy)ethyl succinate, and any salts (e.g. hydrochloride, sodium) or acid forms thereof.

[00139] In a particular embodiment, the monomer M₂ is N-vinylpyrrolidone (NVP to make PVP chains), with the formula:

[00140] In a particular embodiment, the polymer(s) P₂ is poly(N-vinylpyrrolidone) (PVP), suitably a homopolymer thereof.

[00141] Suitably, the molecular weight (M_w) of the polymer chain(s) P₂ are between 2,000 and 2,000,000 g/mol, suitably between 20,000 and 200,000 g/mol, suitably between 30,000 and 150,000, suitably between 60,000 and 130,000.

[00142] Suitably the polymer chain(s) P₂ have a polydispersity index (PDI - M_w/M_n) of between 1 .0 and 2.0, more suitably between 1 .2 and 1 ,8, more suitably between 1 .3 and 1 .7.

Preferred Embodiments of Amphiphilic co-polymer

[00143] Suitably the Pi : P₂ molar ratio of monomer units within the amphiphilic copolymer (i.e. the number of monomer units in Pi relative to the number of monomer units in P₂) is between 10:1 and 1 :20, more suitably between 5:1 and 1 :10, more suitably between 2:1 and 1 :9.

[00144] Suitably the molar ratio of monomer units used in the formation of the amphiphilic co-polymer (i.e. the moles of M₂ used relative to the number of moles of Mi' units in the Pi polymer) is between 10:1 and 1 :10, more suitably between 5:1 and 1 :5, more suitably between 4:1 and 1 :4. [00145] In a particular embodiment, the amphiphilic co-polymer is a PDMS-PVP copolymer. In a particular embodiment, the amphiphilic co-polymer comprises a polydimethylsiloxane (PDMS) silicon polymer backbone Pi attached to which are one or more poly(N-vinylpyrrolidone) (PVP) polymer chains P2. Suitably the one or more poly(N- vinylpyrrolidone) (PVP) polymer chains P₂ are attached to the polydimethylsiloxane (PDMS) silicon polymer backbone Pi via a linker, suitably a vinyloxycarbonyl or allyloxycarbonyl linker, most suitably an allyloxycarbonyl linker. Suitably the the one or more poly(N-vinylpyrrolidone) (PVP) polymer chains P₂ are attached to the terminus or termini of the polydimethylsiloxane (PDMS) silicon polymer backbone Pi . Suitably the polydimethylsiloxane (PDMS) silicon polymer backbone Pi has a molecular weight (M_w) between 1000 and 20000 g/mol, most suitably between 1500 and 10000 g/mol, most suitably between 1500 and 3000 g/mol. Suitably, the molecular weight (M_w) of the polymer chain(s) P₂ are between 60,000 and 130,000 g/mol, most suitably between 60,000 and 100,000 g/mol.

[00146] In some embodiments, two or more hydrophilic polymer chains (P₂) are attached to the silicone polymer backbone Pi (suitably two, one at each terminus of the silicone polymer backbone). Where there are two or more polymer chains P₂, each polymer chain may have the stipulated molecular weight (as per above), or alternatively the above-mentioned molecular weights may relate to the total molecular weight of all P₂ chains in a single amphiphilic co-polymer molecule. However, in some embodiments, only one hydrophilic polymer chain (P₂) is attached to the silicone polymer backbone Pi (suitably at one terminus, optionally due to the other terminus being capped with another unit, such as an alkoxide unit).

Process for the preparation of an amphiphilic co-polymer

[00147] According to a further aspect of the present invention there is provided a process for the preparation of an amphiphilic co-polymer, the process comprising:

wherein Mi is selected from monomers of the formula M1 or a synthetic equivalent thereof (e.g. a cyclic siloxane): Ri

LG-i— Si LG₂

R₂

Formula M1

and the polymerised monomer unit Mi' is selected from polymerised monomer units of formula M1 ':

Formula M1 '

wherein:

Ri and R₂ are each independently selected from:

- hydroxy, amino, vinyl, or allyl;

n is an integer with a value of 2 or more.

Formula 2a Formula 2b

c) polymerising a monomer M₂ in the presence of the functionalised silicone polymer (Pi-L) to grow, from the one or more pre-graft linker group(s) L thereof, one or more hydrophilic polymer chains P₂ (suitably at the terminal monomer unit Mi' thereof) to produce an amphiphilic co-polymer having one or more grafting sites of Formula la and/or Formula lb:

Formula la Formula lb

wherein by itself polymer P₂ is (substantially) soluble in water.

[00148] According to a further aspect of the present invention there is provided an amphiphilic co-polymer obtainable by, obtained by, or directly obtained by a process for the preparation of an amphiphilic co-polymer as defined herein.

[00149] Polymers (Pi and P₂), monomers (Mi , M₂, and corresponding polymerised forms thereof, Mi' and M₂'), linker groups (L, L', and L-LGL), and any associated structural groups and substituents may be as defined herein.

[00150] The silicone polymer backbone Pi is suitably provided by polymerising a monomer of formula M1 , as defined herein. However, it will be understood that other starting materials may be used to obtain the same polymer Pi fseaturing the same polymerised monomeric units Μ . For instance, where Pi is polydimethylsiloxane (PDMS), the polymer may be formed through the polymerisation of a dichlorodimethylsilane in the presence of water. However, as an alternative, the same silicone polymer Pi may be formed via a living anionic polymerisation by reacting hexamethylcyclotrisiloxane (a synthetic equivalent of a monomer of formula M1 ) in the presence of an anionic intiator (e.g. lithium isopropoxide, about 3 mol% relative to the hexamethylcyclotrisiloxane). In such circumstances, each hexamethylcyclotrisiloxane molecule becomes three linked polymerised monomeric units Mi'.

[00151] Where it is desirable to furnish the polymer Pi with either internal grafting sites, branches and/or cross-links, alternative or additional starting materials and monomers/comonomers may be used. For instance, the aforementioned reaction may be conducted in the presence of some methyltrichlorosilane. However, preferably Pi is formed as a linear silicone polymeric backbone. [00152] Suitably polymerisation reactions to form the silicone polymer backbone Pi are controllable, using methods well known in the art, to produce polymers of the desired molecular weight (M_w) and polydispersity.

[00153] Suitably the polymer Pi is provided with terminal hydroxy or oxy-anion groups, which can be functionalised. Alternatively or additionally, the polymer Pi may be formed with internal (non-terminal) hydroxy or oxy-anion groups to enable grafting sites of formulas lb and 2b to be formed. However, in preferred embodiments, the only grafting sites and functionalisable sites are the terminus or termini of the polymer Pi .

[00154] Preparation of the functionalised silicone polymer (Pi-L), and corresponding grafting sites, is suitably achieved by (covalently) attaching a linker group L to a functionalisable group of the polymerisable monomeric unit Mi' at the grafting site, suitably a nucleophilic functionalisable group, such as a group selected from O , OH, NH₂, NHR (wherein R is selected from (1 -8C)alkyl, suitably from (1 -4C)alkyl). This suitably installs a vinyl-containing moiety upon the polymer Pi . This attachment is suitably achieved by reacting the polymer Pi with a reactive (or couplable) form of the linker group L-LGL ("linker reagent"), where L is the pre-graft linker group, and LGi_ is a leaving group, such as halo (e.g. chloro). In a particular embodiment, the pre-graft linker groups are formed by a reaction between a terminal O^" or OH group of the silicone polymer backbone Pi and either one of vinylchloroformate or allylchloroformate.

[00155] Steps (a) and (b) may be, at least to some extent, simultaneous or overlapping. For instance, step (a) may be initiated to commence the formation of the silicone polymer backbone Pi , and step (b) may be initiated (e.g. by the addition of a appropriate linker reagent) before step (a) is complete, such that step (b) may, at least to some extent, regulate or control step (a) (e.g. by terminating polymerisation).

[00156] Suitably both steps (a) and (b) are performed under (substantially) anhydrous conditions. This facilitates higher levels of functionalisation.

[00157] Suitably steps (a) and (b) are performed so that at least 40% of available grafting sites upon the silicone polymer backbone Pi (i.e. at least 40% of functionalisable groups of Pi) are functionalised with a pre-graft linker group, suitably at least 50%, suitably at least 70%, suitably at least 85%, suitably at least 90%. Suitably steps (a) and (b) are performed so that at least 40% of available terminal grafting sites upon the silicone polymer backbone Pi (i.e. at least 40% of functionalisable groups of Pi) are functionalised with a pre-graft linker group, suitably at least 50%, suitably at least 70%, suitably at least 85%, suitably at least 90%. [00158] The product of steps (a) and (b) may be isolated, for example, using techniques well known in the art such as quenching, aqueous work up, etc..

[00159] Step (c) suitably involves attaching or grafting hydrophilic polymeric chain(s) P₂ to grafting sites of the silicone polymer backbone Pi, and suitably involes polymerising a monomer M₂ in the presence of the functionalised silicone polymer (Pi-L) obtained from steps (a) and (b) to grow, from the one or more pre-graft linker group(s) L thereof, one or more hydrophilic polymer chains P2 (suitably at the terminal monomer unit Mi' thereof). This suitably yields the desired amphiphilic polymer. Suitable monomers M₂ are outlined elsewhere herein. Suitably the polymerisation is a free radical polymerisation, and involves reaction of vinyl group(s) of the monomer(s) M₂ (or intermediate polymers formed therefrom) with the vinyl group(s) of the pre-graft linker group L of the functionalise silicone polymer (P1-L). Propagation typically occurs such that polymer chain(s) (P₂) are grown from the grafting site. The nature of the linker of course changes once the pre-graft linker L has reacted with a vinyl moiety of either the monomer(s) M₂ or an intermediate polymer formed therefrom, to yield a post-graft linker L', which is typically a saturated analogue of L.

[00160] Suitably, radical polymerisation may be initiated by a radical initiator. Any suitable radical initiator may be used, and many are known in the art. Suitably the initiator is soluble in the reaction mixture or solvent in which the polymerisation reaction is conducted. In a particular embodiment, 4,4'-Azobis(4-cyanovaleric acid) (ACVA) is used as the radical initiator.

[00161] The radical polymerisation is suitably conducted in an organic solvent, such as tetrahydrofuran (THF).

[00162] The polymerisation reaction may be conducted under vacuum or an inert atmosphere.

[00163] The polymerisation reaction may be conducted at elevated temperatures, for instance a temperature at or above 40°C, or at or above 55°C.

[00164] Suitably, the polymerisation reaction is conducted to produce P₂ chain(s) with a molecular weight (or combined molecular weight per amphiphilic co-polymer molecule) as defined herein.

[00165] The polymerisation to graft/attach one or more P₂ chains to a silicone polymer backbone Pi may be controlled by a variety of methods well known to those skilled in the art, for instance, to derive P₂ chain(s) of a desired molecular weight (M_w). For instance, control may be achieved by judiciously selecting a desirable molar ratio of monomer units used in the formation of the amphiphilic co-polymer (i.e. the moles of M₂ used relative to the number of moles of Mi' units in the Pi polymer).

[00166] The amphiphilic co-polymer may be isolated by methods well known in the art.

Particles

[00167] According to a further aspect of the present invention, there is provided a particulate composition comprising particles of an amphiphilic co-polymer as defined herein, optionally dispersed in a hydrophobic solvent (suitably a hydrophobic solvent that is substantially immiscible with water).

[00168] According to a further aspect of the present invention, there is provided a process for the preparation of a particulate composition, the process comprising contacting a copolymer with (or forming a copolymer in) a hydrophobic solvent, and optionally thereafter removing some or all of said hydrophobic solvent.

[00169] According to a further aspect of the present invention, there is provided a particulate composition obtainable by, obtained by, or directly obtained by a process for the preparation of a particulate composition as defined herein.

[00170] The particulate composition may comprise additional component, such as one or more solvents. Most suitably, any such one or more solvents are organic solvents, suitably hydrophobic organic solvents, suitably aprotic hydrophobic organic solvents, suitably solvents which are (substantially) immiscible with water. The hydrophobic organic solvent(s) are suitably selected from benzene, carbon tetrachchloride, chloroform, chlorobenzene, cyclohexane, heptane, pentane, tetrahydrofuran, toulene, xylene, hexamethyldisiloxane (or any length PDMS that is a liquid).

[00171 ] The size of the particles of the amphiphilic co-polymer depends on a number of factors, including the length (or molecular weight) of the hydrophilic polymer chain(s) P₂, the overall hydrophobic/hydrophilic balance, and the polarity of any solvents in which the particles are dispersed, suspended, or dissolved. Generally speaking, the larger the P₂ chains, the larger the particles will be in hydrophobic organic solvents but the smaller the particles will be in hydrophilic or aqueous solvents.

[00172] The average particle size of particles of the amphiphilic co-polymer is suitably between 1 and 10 μηι in hydrophobic organic solvents, whilst average particle size of particles of the amphiphilic co-polymer is suitably between 200-600nm in water. [00173] In a particular embodiment, the particulate composition comprises the amphiphilic co-polymer dispersed or dissolved within a silicone or siloxane-based hydrophobic solvent, such as hexamethyldisiloxane. The concentration of the amphiphilic co-polymer is suitably between 0.1 and 100 mg/mL, suitably between 1 and 10 mg/mL, suitably about 5mg/ml_.

[00174] The particles of the amphiphilic co-polymer are suitably micelles, especially in organic and/or hydrophobic solvents, such as hexamethyldisiloxane or dichloromethane. In such solvents, the core of the micelle particles is hydrophilic and (substantially) composed of the hydrophilic polymer chain(s) P₂, whereas the shell of the micelle particles is hydrophobic and (substantially) composed of the silicone polymer backbone Pi . The configuration of such micelles enables them to encapsulate hydrophilic agents and, when required, such encapsulated hydrophobic agents can be encouraged to be released in a controlled manner.

[00175] Such particles increase the wettability of organic/hydrophobic solvents, enabling organic/hydrophobic solvents to tolerate higher water levels before clouding or phase separation occurs.

Agent-loaded Particles

[00176] According to a further aspect of the present invention, there is provided an agent-loaded particulate composition, comprising particles of an amphiphilic copolymer as defined herein, a hydrophilic agent, and optionally a hydrophobic solvent and/or a hydrophilic solvent.

[00177] According to a further aspect of the present invention, there is provided a process for the preparation of an agent-loaded particulate composition, the process comprising contacting a particulate composition as defined herein with a hydrophilic agent, optionally in the presence of a hydrophilic solvent (suitably a hydrophilic solvent that is substantially miscible with water, most suitably water itself).

[00178] According to a further aspect of the present invention, there is provided an agent-loaded particulate composition obtainably by, obtained by, or directly obtained by a process for the preparation of an agent-loaded particulate composition as defined herein.

[00179] The hydrophilic agent may be as defined herein.

[00180] Having formed particles of the amphiphilic co-polymer, a hydrophilic agent (e.g. a hydrophilic antimimcrobial agent) may be encapsulated within the core of such particles, optionally for later deliver/release. [00181] Suitably the hydrophilic agent will be pre-dissolved in a hydrophilic solvent, such as water, before being contacted with the particulate composition.

[00182] The hydrophilic agent is suitably absorbed/encapsulated within the particles, suitably within the core thereof, which is itself suitably hydrophilic in character (e.g. as a micelle).

[00183] High loadings of hydrophilic agent are achievable, especially since after the encapsulation of some hydrophilic agent there is evidence to suggest that the resulting particles aggregate further to facilitate encapsulation of more hydrophilic agent. Suitably, the weight ratio of hydrophilic agent : amphiphilic co-polymer is between 1 :100 and 10:1 , suitably between 1 :50 and 1 :1 , suitably between 1 :20 and 1 :2, suitably between 1 :10 and 1 :5.

A Silicone-based Composition

[00184] According to a further aspect of the present invention, there is provided a silicone-based composition, comprising a silicone matrix material, an amphiphilic copolymer as defined herein, and optionally a hydrophilic agent (optionally provided in conjunction with the amphiphilic co-polymer as part of an agent-loaded particulate composition as defined herein).

[00185] The hydrophilic agent is optional within the silicone-based composition because it may, in principle, be absorbed or encapsulated within particles of amphiphilic co-polymer once the silicone-based composition has been incorporated into a product (e.g. medical article), such as a wound dressing. However, in preferred embodiments, the silicone-based composition comprises the hydrophilic agent (suitably in advance of any incorporation of said composition within a product).

[00186] Suitably, the amphiphilic co-polymer is provided in the form of particles (as defined in relation to the particulate composition) within the silicone-based composition, suitably having been pretreated with an organic/hydrophilic solvent. Suitably the particles are micelle particles, suitably with a hydrophilic core and a hydrophobic shell.

[00187] The amphiphilic co-polymer or particles thereof is suitably mixed with the silicone matrix material, suitably (substantially) uniformly dispersed through said silicone matrix material.

Silicone Matrix Material [00188] The silicone matrix material is suitably a silicone or polysiloxane (suitably a polymer P₃ comprising a chain of polymerised monomer units M₃' derived or derivable from a monomer M₃). The silicone matrix material is suitably (substantially) insoluble in water. Preferably the water-solubility of the silicone matrix material is less than or equal to 1 g/L, suitably less than or equal to 0.1 g/L.

[00189] The silicone matrix material may be linear, branched, or cross-linked (or curable to become cross-linked, suitably if a cross-linking/curing catalyst, such as platinum, is present within the silicone matrix material).

[00190] The silicone matrix material may independently have any of the definitions outlined herein in relation to the silicone polymer backbone Pi . As such, the silicone matrix material may be considered a polymer P₃ (suitably comprising a chain of polymerised monomer units M₃' derived or derivable from a monomer M₃), and any of the parameters, features or structures defined herein in relation to Pi , Mi and Mi' may independently apply to corresponding parameters, features or structures of P₃, M₃, and M₃'. As such, though P₃, M₃, and M₃' may have any of the values defined herein in relation to Pi , Mi and Μ , the exact values of P₃, M₃, and M₃' may be dissimilar to those of Pi , Mi and Mi' (for instance, molecular weight) - i.e. P₃ and Pi may not be the same. However, in preferred embodiments, the silicone matrix material (P₃) comprises the same polymerised monomeric units (Μ₃'), derived or derivable from the same monomer M₃, as the silicone polymer backbone (Pi) - i.e. Μι'=Μ₃'. Moreover, in some embodiments, the silicone matrix material (P₃) suitably has a molecular weight (M_w) that is between 50 and 150% of that of the silicone polymer backbone (Pi) (i.e. the ratio of molecular weights of P₃ to Pi is between 1 :2 and 2:3), suitably between 70 and 130% of the silicone polymer backbone (Pi), suitably between 90 and 1 10% of the silicone polymer backbone (Pi). Most suitably the silicone matrix material (P₃) has a molecular weight (M_w) that is (substantially) higher thanthat of the silicone polymer backbone (Pi).

[00191] In some embodiments, P₃, M₃, and M₃' may have parameters, features or structures that are different to or outside the scope of those defined in relation to Pi , Mi [00192] The silicon matrix material is preferably suitable for use in a wound dressing, especially as a wound contact surface (i.e. which mitigates against wound trauma and irritation). Suitably, the silicone matrix material is suitable for use in soft silicone dressings.

[00193] In a particular embodiment, the silicone matrix material (P₃) is selected from polydimethylsiloxane (PDMS), polydiethylsiloxane (PDES), polymethylethylsiloxane (PMES), polydiphenylsiloxane (PDPS), and polymethylphenylsiloxane (PMPS). In a particular embodiment, the silicone matrix material (P₃) is polydimethylsiloxane (PDMS).

[00194] Suitably the silicone matrix material (P₃) has a molecular weight (M_w) or a molecular weight (M_n) between 1000 and 500,000 g/mol, suitably between 10,000 and 400,000 g/mol, suitably between 50,000 and 200,000 g/mol. In a particular embodiment, the polymer Pi has a molecular weight (Mw) or a molecular weight (M_n) between 80,000 and 130,000 g/mol.

[00195] Suitably the silicone matrix material (P₃) has a viscosity between 10000 and 70000 mPa.s in accordance with the DIN EN ISO 3219 standard testing protocol, more suitably between 15000 and 60000.

[00196] The silicone matrix material may comprise one or more silicone components. Where the silicone matrix material comprises two or more silicone components, unless stated otherwise, any values given herein in relation to the properties of the overall silicone matrix materials suitably applies to the overall combination of the two or more silicone components (whether tested as a mixture or taken as a weighted average of values for the individual components)

[00197] The silicone matrix material is suitably a silicone gel. Suitably the silicone gel has a viscosity between 10000 and 70000 mPa.s in accordance with the DIN EN ISO 3219 standard testing protocol, more suitably between 15000 and 60000. Suitably the silicone gel has a density between 0.95g/cm³ and 1 .05g/cm³. In some embodiments, the silicone gel (or part thereof) is cross-linked or is otherwise curable to form cross-links (e.g. if a cross-linking/curing catalyst, such as platinum, is present). The silicone gel may comprise a mixture of two or more different batches or types of silicone. In a particular embodiment the silicone gel comprises a first silicone component and a second silicone component. Suitably the silicone gel consists essentially of the first and second silicone component. The weight ratio of the first to second silicone component is suitably between 10:1 and 1 :10, more suitably between 2:1 and 1 :2, most suitably about 1 :1 . The first and second silicone component may each have a density between 0.95g/cm³ and 1 .05g/cm³. The first silicone component suitably has a viscosity between 10000 and 50000 mPa.s. Suitably the first silicone component has a viscosity between 10000 and 30000 mPa.s, most suitably between 15000 and 25000 mPa.s, and the second silicone component suitably has a viscosity between 40000 and 70000 mPa.s, more suitably between 50000 and 60000 mPa.s, where viscosity is measured in accordance with the DIN EN ISO 3219 standard testing protocol. The silicone matrix material may be SILPURAN® 21 10 A/B Silicone Gel, which is commercially available from Wacker Chemie AG. Hvdrophilic Agent

[00198] The hydrophilic agent is suitably an agent to be desirably encapsulated or absorbed within particles of the amphiphilic co-polymer.

[00199] The hydrophilic agent is suitably (substantially) water soluble, suitably having a water solubility of greater than or equal to 2g/L, suitably greater than or equal to 10g/L, suitably greater than or equal to 50g/L.

[00200] The agent-loaded particulate composition, or silicone-based composition, or products derived therefrom may comprise one or more hydrophilic agents (suitably as defined herein).

[00201] Suitably the hydrophilic agent is a therapeutic agent. Suitably, the therapeutic agent is present within the agent-loaded particulate composition, silicone-based composition, or products derived therefrom, in a therapeutically effect amount to treat the relevant medical condition or disorder (e.g. wound infection). Suitably the therapeutic agent is for treating wounds, a skin condition or disorder (or symptoms thereof), or disease or condition for which the therapeutic agent is indicate, where said thereapeutic agent may be absorbed through the skin. Most suitably the therapeutic agent is for treating wound infections.

[00202] Suitably the hydrophilic agent (or therapeutic agent) is a hydrophilic antimicrobial agent (i.e. an antimicrobial agent that is water soluble, suitably as defined herein in relation to the hydrophilic agent). The hydrophilic antimicrobial agent may be an antibacterial agent, an antifungal agent, an antiviral agent, or an antiparasitic agent. Suitably the antimicrobial agent is a single compound or a mixture of antimicrobial compounds.

[00203] The hydrophilic antimicrobial agent may be selected from the group including silver, iodine and derivates (e.g. Povidone iodine (PVP-I), Cadexomer iodine (CI)), chlorhexidine, Polyhexamethylene biguanide (PHMB), Ethylene diamine tetra acetic acid (EDTA), Chlorhexidine (CHX), Quaternary ammonium compounds (QACs) and derivatives, Octenidine hydrochloride (OH), Benzalkonium chloride (BAC), or may be a mixture thereof and/or mixed with an additional therapeutic agent optionally as defined herein. In a particular embodiment, the antimicrobial agent is selected from Chlorhexidine digluconate and benzalkonium chloride or a mixture thereof. [00204] The hydrophilic agent is suitably one or more non-solvent compounds. Suitably none of the one or more compound(s) of the hydrophilic agent have a boiling points of less than 120°C, suitably not less than 150°C.

Other Components

[00205] Suitably the silicone-based composition comprises one or more solvents, suitably one or more solvents used in the formation of the silicone-based composition. Suitably the silicone-based composition comprises a hydrophobic solvent and/or a hydrophilic solvent.

[00206] Where the silicone-based composition comprises a hydrophobic solvent, said solvent is suitably that used in conjunction with the amphiphilic co-polymer to form particles thereof, for example, hexamethyldisiloxane or dichloromethane. Most suitably the hydrophobic solvent is a silicon-based, silicone-based, or siloxane-based solvent, since this is suitably more compatible with the silicone matrix material with which it is mixed within the silicone-based compositions of the invention.

[00207] Where the silicone-based composition comprises a hydrophilic solvent, said solvent is suitably that use to pre-dissolve a hydrophilic agent. Suitably said solvent is that used in the formation of an agent-loaded particulate composition, where the hydrophilic agent is pre-dissolved in said solvent prior to its contact an ultimate absorption/encapsulation within the particles of amphiphilic co-polymer. Most suitably, said hydrophilic solvent is water.

[00208] In a particular embodiment, the silicone-based composition comprises both of a hydrophobic solvent and a hydrophilic solvent. In such cases, suitably the silicone-based composition comprises more by weight of hydrophobic solvent than hydrophilic solvent, suitably at least two times more, suitably at least three times more, suitably at least 5 times more.

Preferred Embodiments of Silicone-based composition

[00209] In a particular embodiment, the silicone-based composition comprises a PDMS silicone matrix material (P3) and an amphilphilic co-polymer as defined herein (preferably one of the preferred embodiments thereof). Suitably, the weight ratios of amphiphilic co-polymer : silicone matrix material is between 1 :1000 and 1 :10, most suitably between 1 :200 and 1 :50, most suitably about 1 :100 (i.e. 1 % by weight amphiphilic copolymer relative to the weight of the silicone matrix material). In preferred embodiments, the silicone-based composition also comprises a hydrophilic agent (most suitably a hydrophilic antimicrobial agent), suitably with a preferred loading ratio.

[00210] In a particular embodiment, the silicone-based composition comprises:

- 3,000-95,000 parts by weight silicone matrix material (most suitably PDMS); - 0.1 -2,500 parts by weight amphiphilic co-polymer (most suitably a PDMS-PVP copolymer, most suitably as defined in one of the preferred embodiment); and

1 -1 ,000 parts by weight hydrophilic agent (most suitably a hydrophilic therapeutic agent, most suitably an antimicrobial agent, most suitably as defined in one of the preferred embodiments thereof);

wherein optionally any remaining weight balance consists essentially of a hydrophilic and/or a hydrophobic solvent (suitably as defined in one of the preferred embodiments).

[00211] In a particular embodiment, the silicone-based composition comprises:

- 20,000-90,000 parts by weight silicone matrix material (most suitably PDMS);

100-1 ,000 parts by weight amphiphilic co-polymer (most suitably a PDMS-PVP co- polymer, most suitably as defined in one of the preferred embodiment); and

10-500 parts by weight hydrophilic agent (most suitably a hydrophilic therapeutic agent, most suitably an antimicrobial agent, most suitably as defined in one of the preferred embodiments thereof);

[00212] In a particular embodiment, the silicone-based composition comprises:

- 25,000-50,000 parts by weight silicone matrix material (most suitably PDMS);

- 200-500 parts by weight amphiphilic co-polymer (most suitably a PDMS-PVP copolymer, most suitably as defined in one of the preferred embodiment); and - 100-200 parts by weight hydrophilic agent (most suitably a hydrophilic therapeutic agent, most suitably an antimicrobial agent, most suitably as defined in one of the preferred embodiments thereof);

[00213] In a particular embodiment, the silicone-based composition comprises:

- 3-95 wt% silicone matrix material (most suitably PDMS); - 0.0001 -2.5 wt% amphiphilic co-polymer (most suitably a PDMS-PVP co-polymer, most suitably as defined in one of the preferred embodiment); and

- 0.001 -1 .0 wt% Hydrophilic agent (most suitably a hydrophilic therapeutic agent, most suitably an antimicrobial agent, most suitably as defined in one of the preferred embodiments thereof);

[00214] In a particular embodiment, the silicone-based composition comprises:

- 20-90 wt% silicone matrix material (most suitably PDMS);

- 0.1 -1 .0 wt% amphiphilic co-polymer (most suitably a PDMS-PVP co-polymer, most suitably as defined in one of the preferred embodiment); and

- 0.01 -0.5 wt% Hydrophilic agent (most suitably a hydrophilic therapeutic agent, most suitably an antimicrobial agent, most suitably as defined in one of the preferred embodiments thereof);

[00215] In a particular embodiment, the silicone-based composition comprises:

- 25-50 wt% silicone matrix material (most suitably PDMS);

- 0.2-0.5 wt% amphiphilic co-polymer (most suitably a PDMS-PVP co-polymer, most suitably as defined in one of the preferred embodiment); and

- 0.1 -0.2 wt% Hydrophilic agent (most suitably a hydrophilic therapeutic agent, most suitably an antimicrobial agent, most suitably as defined in one of the preferred embodiments thereof);

[00216] Suitably, the weight ratio of amphiphilic co-polymer to hydrophilic agent is between 100:1 and 1 :10, suitably between 50:1 and 1 :2, suitably between 20:1 and 1 :1 , most suitably between 10:1 and 2:1 , suitably between 8:1 and 5:1 .

[00217] Suitably, the weight ratio of amphiphilic co-polymer to silicone matrix material is between 1 :100,000 and 1 :1 , suitably between 1 :1 ,000 and 1 :5, suitably between 1 :500 and 1 :10, more suitably between 1 :200 and 1 :50, most suitably between 1 :150 and 1 :80. [00218] Suitably the combined weight of the silicone matrix material, amphiphilic copolymer, and hydrophilic agent constitute at least 3 wt% of the total silicone-based composition, more suitably at least 10 wt%, more suitably at least 20 wt%, most suitably at least 30 wt%. Suitably the combined weight of the silicone matrix material, amphiphilic co-polymer, and hydrophilic agent constitute at most 95 wt% of the total silicone-based composition, more suitably at most 90 wt%, more suitably at most 80 wt%, most suitably at most 40 wt%.

[00219] Suitably the combined weight of any hydrophobic and/or hydrophilic solvents constitutes at least 5 wt% of the total silicone-based composition, suitably at least 10 wt%, suitably at least 20 wt%, most suitably at least 60 wt%. Suitably the combined weight of any hydrophobic and/or hydrophilic solvents constitutes at most 97 wt% of the total silicone-based composition, suitably at most 90 wt%, suitably at most 80 wt%, most suitably at most 70 wt%.

Process for the preparation of a silicone-based composition

[00220] According to a further aspect of the present invention, there is provided a process for the preparation of a silicone-based composition, the process comprising mixing a silicone matrix material together with either an amphiphilic co-polymer (optionally also with a hydrophilic agent) or an agent-loaded particulate composition as defined herein.

[00221] According to a further aspect of the present invention, there is provided a silicone-based composition obtainable by, obtained by, or directly obtained by a process for the preparation of a silicone-based composition as defined herein.

[00222] Most suitably the amphiphilic co-polymer is first mixed with, dissolved, dispersed, or suspended in a hydrophobic solvent to produce a particulate composition, suitably as defined herein. In some embodiments, this particulate composition may then be mixed with a silicone matrix material (i.e. without necessarily pre-forming an agent- loaded particulate composition, since the amphiphilic co-polymers may optionally be contacted with a hydrophilic agent, to encapsulate said hydrophilic agent with the amphiphilic co-polymer particles, after an initial pre-treated silicone-based composition has first been formed - post-treatment of this silicone-based composition with a hydrophilic agent, suitably pre-dissolved in a polar solvent, suitably produces a silicone-based composition comprising the hydrophilic agent).

[00223] The hydrophilic agent is suitably pre-dissolved in a polar solvent, such as water, to produce a hydrophilic agent solution. Preferably this hydrophilic agent solution is mixed with the aforementioned particulate composition (comprising the amphiphilic copolymer mixed with a hydrophobic solvent) to form an agent-loaded particulate composition. The agent-loaded particulate composition is then suitably mixed with a silicone matrix material to form the silicone-based composition.

[00224] The silicone-based composition may be further processed to yield a processed silicone-based composition. Such processed silicone-based compositions may still be considered silicone-based compositions, since the relative amounts of silicone matrix material, amphiphilic co-polymer, and optional hydrophilic agent generally remain the same, though one or more of these components may be transformed (e.g. the silicone matrix material may be cured to produce a cured silicone matrix material - e.g. where it becomes cross-linked where a cross-linking agent and/or cross-linking initiator or catalyst is present). Moreover, some or all solvent(s) may be removed in some or all of the further processing steps. As such, the parts by weight definitions of the silicone-based compositions are somewhat more relevant than the wt% definitions.

[00225] Further processing of the silicone-based composition may involve heating, drying, and/or curing the silicone-based composition (i.e. to produce a heated, dried, and/or cured silicone-based composition), for instance by heating the composition at elevated temperature (e.g. at least 40°C, suitably at least 50°C, most suitably at least 55°C) for a pre-determined amount of time, optionally under vacuum.

[00226] Further processing may involve treating or contacting the silicone-based composition with a hydrophilic agent (suitably pre-dissolved in a polar solvent).

[00227] Further processing may involve transforming the physical form of the silicone- based composition, for instance to produce a film or membrane. For example, the silicone- based composition (especially where it is a viscous composition, dispersion, suspension, emulsion, or solution) may be transformed into a film or coating layer, for instance through being "drawn down" with a K bar. Such film, layer, or coating formation may preceed one of the other further processing steps (e.g. preceeds heating/curing).

Medical Articles and Wound Dressings

[00228] According to a further aspect of the present invention, there is provided a medical article (suitably for contact with skin and/or a wound), comprising an amphiphilic co-polymer as defined herein, a particulate composition as defined herein (optionally dried and/or cured), an agent-loaded particulate composition as defined herein, or a silicone- based composition as defined herein. [00229] According to a further aspect of the present invention, there is provided a process for the preparation of a medical article, the process comprising incorporating within a medical article an amphiphilic co-polymer as defined herein, a particulate composition as defined herein (optionally dried and/or cured), an agent-loaded particulate composition as defined herein, or a silicone-based composition as defined herein, and optionally thereafter contacting said medical article with a hydrophilic agent.

[00230] According to a further aspect of the present invention, there is provided a medical article obtainable by, obtained by, or directly obtained by a process for the preparation of a medical article as defined herein.

[00231] According to a further aspect of the present invention, there is provided a medical article (suitably for contact with skin and/or a wound), comprising silicone-based composition as defined herein, which silicone-based composition comprises a silicone matrix material; an amphiphilic co-polymer comprising a silicone polymer backbone Pi and one or more hydrophilic polymer chains P₂ attached to the silicone polymer backbone Pi as defined herein, optionally via a linker; and a hydrophilic agent as defined herein.

[00232] The medical article may be one of a number of articles well known in the art, which are designed for contact with the skin (especially human skin) and/or skin wounds. The medical article may include dressing, plasters, bandages, patches, etc. Incorporation of the amphiphilic co-polymer, particulate composition, agent-loaded particulate composition, or silicone-based composition within the medical article may suitably involve either impregnating the medical article with one of the aforementioned components, or applying one of the aforementioned components to the medical article, for example to the surface thereof, especially to a skin or wound contact surface thereof, so as to form a coating or film layer of one of the aforementioned components. The component(s), once incorporated within the medical article, may be optionally further processed as defined in relation to the silicone-based compositions (e.g. dried or cured or post-treated with a hydrophilic agent, suitably pre-dissolved in a polar solvent).

[00233] In a particular embodiment, the medical article is a wound dressing.

[00234] According to a further aspect of the present invention, there is provided a wound dressing, comprising an amphiphilic co-polymer as defined herein, a particulate composition as defined herein (optionally dried and/or cured), an agent-loaded particulate composition as defined herein, or a silicone-based composition as defined herein.

[00235] According to a further aspect of the present invention, there is provided a process for the preparation of a wound dressing, the process comprising incorporating within a wound dressing (e.g. by coating an outer surface of a wound dressing or partially assembled wound dressing, suitably an outer surface intended for contact with skin or a wound) an amphiphilic co-polymer as defined herein, a particulate composition as defined herein (optionally dried and/or cured), an agent-loaded particulate composition as defined herein, or a silicone-based composition as defined herein, and optionally thereafter contacting said wound dressing (e.g. the outer surface thereof) with a hydrophilic agent.

[00236] According to a further aspect of the present invention, there is provided a wound dressing obtainable by, obtained by, or directly obtained by a process for the preparation of a wound dressing as defined herein.

[00237] The wound dressing is suitably designed for contact with the skin (especially human skin) and/or skin wounds. The wound dressing suitably comprises an adhesive portion to facilitate adhesion to the skin. However, suitably the adhesive portion is a different potion of the wound dressing to that in which the amphiphilic co-polymer, particulate composition, agent-loaded particulate composition, or silicone-based composition has been/is incorporated. Suitably the adhesive portion is not designed for contact with a wound, whereas a portion of the wound dressing in which one of the amphiphilic co-polymer, particulate composition, agent-loaded particulate composition, or silicone-based composition has been/is incorporated is suitably designed for wound contact. Incorporation of the amphiphilic co-polymer, particulate composition, agent- loaded particulate composition, or silicone-based composition within the wound dressing suitably involves applying one of the aforementioned components to the wound dressing, for example, to the surface thereof, especially to a skin or wound contact surface thereof, so as to form a coating or film layer of one of the aforementioned components. The component(s), once incorporated within the wound dressing, may be optionally further processed as defined in relation to the silicone-based compositions (e.g. dried or cured or post-treated with a hydrophilic agent, suitably pre-dissolved in a polar solvent).

[00238] According to a further aspect of the present invention, there is provided a kit of parts comprising a medical article or a wound dressing as defined herein, and a hydrophilic agent. With such kits, the hydrophilic agent may be incorporated in the medical article or wound dressing at an appropriate time (e.g. shortly prior to use).

[00239] According to a further aspect of the present invention, there is provided a use of an amphiphilic co-polymer as defined herein, a particulate composition as defined herein, an agent-loaded particulate composition as defined herein, or a silicone-based composition as defined herein, for delivering a hydrophilic agent (e.g. an antimicrobial agent) to a wound that is infected, suspected to be infected, or at risk of being infected. EXAMPLES

Materials and Equipment

[00240] All materials were used as received unless otherwide indicated. Hexamethyltrisiloxane (99%) was dried in a desiccator for 24 hr prior to use. N- vinylpyrrolidone (>97%) was distilled under reduced pressure to remove inhibitors present.

[00241] Tetrahydrofuran (THF) was obtained from the Grubbs dry solvent system.

¹H and ¹³C NMR

[00242] All NMR spectra were recorded at ambient temperature on Bruker AV-250, AV- 400 or DRX-500 at 250, 400 or 500MHz (64 scans averaged per spectrum). Samples of mass 20-40mg were dissolved in deuterated chloroform (CDCI₃) or alternative solvent system, filtered and placed in 7mm NMR tubes.

MALDI TOF Mass Spectroscopy

[00243] MALDI-MS spectrum was obtained by using Tof Spec-2E Spectrometer by using N2 laser at 337 nm (pulse rate of 10 Hz) with positive polarity in the linear mode. The accelerating voltage was 20 kV. The applied pressure was 3.59χ 10 ⁷ Torr. The sample was prepared by taking 20 mg of polymer dissolved in 0.5 ml THF. 2-[(2E)-3-(4-tert- Butylphenyl)-2-methylprop-2-enylidene] malononitrile (DCTB) was used as matrix (20 mgcnr³). 0.5 mg Sodium trifluroacetate was dissolved in 0.5 ml THF used as ionization promoter. Than after mixing them together by 1 :1000:10 ratio 1 μΙ of this solution was applied to Matrix plate. The matrix was dried and experiment was carried out.

Gel permeation elution chromatography

[00244] Both Normal and reverse phase GPEC analysis were performed using an LC- 20ADXR Prominence pump and SIL-20AXR Prominence auto sampler with a CTO-10AS column oven set to 40°C using analytical grade solvents with an Shimadza ELSD-LT detector with the data being analysed by LC Solution software 1 .25. The machine was equilibrated for 1 hr prior to use and a 5minute equilibrium period was done between each sample run to allow for solvent gradient to reach 100% of chosen solvent before the next run.

Normal phase [00245] The column used for all normal phase runs was a Genesis Ci₈ 4μηι column. The gradient performed was as follows; Hexane 100% for 4minutes, up to 20% IPA over next 2minutes then hold for 4minutes, up to 40% IPA over next 2minutes and hold for 4minutes then increase the gradient to 100% IPA over the next 5minutes.

Reverse phase

[00246] The column used for all reverse phase runs was a Nova-Pak silica 4μηι 3.9x150mm cartridge. The gradient performed was as follows; IPA 100% for 4minutes, up to 20% Hexane over next 2minutes then hold for 4minutes, up to 40% Hexane over next 2minutes and hold for 4minutes then increase the gradient to 100% Hexane over the next 5minutes.

ATR-FTIR (attenuated total reflection Fourier transform infared spectroscopy)

[00247] All samples were placed without dilution on the crystal of a Bruker ALPHA platinum - ATR and analysed using OPUS 7.5. The crystal was cleaned with methanol between sample loadings.

Elemental Analysis

[00248] Elemental Analysis was performed on a Perkin-Elmer 2400 CHNS/O Series 2 Elemental Analyser. 5-1 Omg of sample was combusted in the presence of excess oxygen and combustion reagent to form C0₂ and water. Levels of each element were detected using a thermal conductivity detection system.

Particle Sizing Analysis

[00249] Particle size analysis was carried out on a Brookhaven Instruments Corporation ZetaPALS Zeta Potential Analyser with the 90Plus/BI-MAS Multi Angle Particle Sizing Option. Samples were prepared at 0.5% concentration (5mg/ml) by either dissolving directly in the required solvent or by using the solvent switch method. Polymer samples were dissolved in organic solvent (hexamethyldisiloxane) then ultrapure H₂0 was added dropwise to the stirring solutions. Samples were left to stir for several hours for the organic solvent to evaporate. 15μΙ of sample was then added to 3ml of 10mmol KCI solution, sonicated for 20 seconds, filtered through a 1 μηι filter. Measurements were made at 25°C unless otherwise stated. 10 analysis runs were made in triplicate for each sample. Zeta Potential Measurements

[00250] Zeta potentials were measured on a Brookhaven Instruments Corporation ZetaPALS Zeta Potential Analyser. Samples were prepared in ultrapure H₂0 using the same method as for particle size analysis. 15μΙ of sample was added to 1 .5ml of 1 mmol KCI solution. Measurements were made at 25°C in triplicate for each sample in 5 cycles of 2 minute runs.

Thermogravimetric Analysis (TGA)

[00251] A Perkin Elmer TGA pyris 1 was used with the pan being supported via a "hangdown" position. With Pyris manager 1 1 .1 software being used to collate data.

Size exclusion chromatography

[00252] Molecular weight and molecular weight distributions were measured relative to PMMA standards by GPC with PL gel mixed-B (10 μηι particle size, 100-10⁶ A pore size, effective MW ranges 10³ - 10⁶, 3x 30 cm + guard columns) (polymer laboratories UK) on an Rl detector. The mobile phase was Chloroform (GPC grade) set to a flow rate of 1 mlmin ¹. Sample concentration used was 2 mgml ¹ , filtered prior to injection. Samples were injected manually. Example 1 - Preparation of Functionalised Silicone Polymer Backbone (P -L)

Scheme 1 - Functionalisation of silicone polymer backbone at the terminal OH or O with either vinyl or all yl chloroformate

[00253] PDMS functionlised macro-monomers were prepared under a nitrogen atmosphere using living anionic polymerization. For example, a solution of hexamethylcyclotnsiloxane (0.03 mol, 7 g) and lithium isopropoxide (3mol %, 0.4 mL 2M solution in THF) in THF (10 mL) was injected into a pre-sealed glass tube. The solution was stirred at room temperature for 3hrs and then allyl chloroformate (3mol %) was injected into the solution. The reaction mixture was ultrasonicated for 20 min and then stirred at room temperature for 24hrs. The solvent was evaporated by rotary evaporation under reduced pressure and the liquid oligomer was dissolved in chloroform. The solution was washed with water twice and the organic layer collected. Chloroform was removed by rotary evaporation and the product was dried under vacuum at 40°C. The functionalised oligomer was then characterized by ¹ H NMR, SEC and MALDI ToF mass spectrometry.

Allyl PDMS Macro-monomer: Ή NMR: (400 MHz, CDCI₃) δ/ppm:. 0.15 (br, 3H, -CH₃), 1 .25 (d, 3H, -CH₃), 4.1 (sep, 1 H, CH), 4.25 (d, 2H, CH₂), 5.1 (d, 1 H, C=CH), 5.3 (d, 1 H C=CH), 5.9 (br, 1 H, C=CH)

Vinyl PDMS Macromonomer: ¹H NMR: (400 MHz, CDCI₃) δ/ppm: 0.15 (br, 3H, -CH₃), 1 .25 (d, 3H, -CH₃), 4.1 (sep, 1 H, CH), 5.4 (d, 1 H, C=CH), 5.9 (d, 1 H C=CH), 7 (d, 1 H C=CH)

[00254] PDMS functionalised marcomonomers were synthesised as stated above. The ratio of initiator (ILP) to starting material (HMCTS) was tailored to obtain average molecular weights of approximately 2, 5 and 10K for both the allyl and vinyl functionalised macro- monomers. The Mw, Mn, PDI, percentage functionality (%Fn) and yield are given below in Table 1 . The percentage functionality was calculated using ¹ H NMR via integration of relevant peaks which will be addressed later. Second confirmation of %Fn was calculated by MALDI TOF mass spectroscopy by comparing the area under the hydroxyl terminated peak and ally terminated peaks, with an average obtained using each peak over the entire spectrum.

Table 1 - Characterisation of functionalised silicone polymers

12 1 1 .5 1 .08

1 :40 (high Mw) 30 50 18 40

33 30.4 1 .19

[00255] The average M_w, M_n and PDI were all determined by SEC using PMMA as the calibration standard, the original aim of macro-monomers to be produced was 2 (low Mw), 5 (medium Mw) and 10K (high Mw) which appears to have been largely achieved. The general trend of macromonomer is an apparent increase in size as intended. The poly dispersities index of all samples were narrow showing a typical bell curve distribution, however, the vinyl reacted macro-monomer had two distinct populations shown in FIG.1 .

[00256] FIG. 1 shows a SEC chromatograph of (a): allyl-functionalised silicone polymer, with increasing size from left to right; and (b): vinyl-functionalised silicone polymer, again with increasing size from left to right.

[00257] Upon analysis of SEC chromatographs given in FIG. 1 it can be seen that the allyl-functionalised PDMS polymer (or macromonomer) produces single distributions of macromonomer, with an increase in size when increasing the ratio of initiator to starting material as intended. Whilst this trend of increasing in size can generally be seen with the vinyl-functionalised PDMS macromonomer. These macromonomers however, have a distinct bimodal distribution present regardless of average molecular weight targeted. Using origin software these peaks were deconvoluted using a Gaussian fit model to represent the two individual populations which is shown below in FIG. 2. These deconvoluted peaks were then used to determine the M_w and M_n of each peak, which are summarised below in Table 2.

FIG. 2 shows low (a), medium (b), and high (c) molecular weight according to above FIG. 1 and Table 1 . Peak colours; dark grey: 1 ^st deconvoluted peak, light grey: 2^nd deconvoluted peak, black: raw data.

Table 2 - Deconvoluted SEC bimodal distribution of vinyl macromonomers using origin to obtain individual peaks Mw, Mn, Mz and PDI.

[00258] The reason behind these two distinct populations forming may be due to the difference in reactivity between the allyl and vinyl chloroformate, with the latter being much less reactive so the polymerisation is not being terminated accordingly so is as a result less controlled and two populations are formed.

[00259] The percentage functionality of these PDMS macromonomers was initially low (left %Fn in Table 1 ) this was thought to be due to the presence of water within the reaction, essentially quenching the oxygen anion of the PDMS before the addition of the chloroformate, or reacting directly with the chloroformate, as a result efforts were made to make the reaction conditions much drier. The nitrogen supply was passed over CaCI₂, HMCTS was dried 24hrs prior to use in a vacuum desiccator and all glass ware was dried in a 70°C oven for 24hrs prior to use. This yielded a significantly higher %Fn (right %Fn in Table 1 ). The reduction in water content of HMCTS via ¹ H NMR is shown below in FIG. 3.

[00260] FIG. 3 shows ¹ H NMR of HMCTS showing the integral peaks of H₂0 and CH₃ of HMCTS. Upon comparison of the ratio of integrals of the peaks gave a water percentage content of the material, (a): Before drying, 10% H₂0, (b): After 24hrs of drying, 4% H₂0.

[00261] Both the structure and functionality of macromonomer was determined by ¹ H NMR. The structure closely matches to what is to be expected clearly showing the vinyl peaks of the functionalised macromonomer (peaks c,d) in the ¹ H NMR which is shown below in FIG. 4.

[00262] FIG. 4 shows ¹ H NMR of the a functionalised PDMS macromonomer

[00263] The %Fn was calculated using the intergration of proton peaks a, i in the case of the allyl macromonomer. Calculating the %Fn vinyl had to be calculated using peaks c,d and i. This is due to the presence of proton peak h in both functionalised and non- functionalised PDMS macromonomer whilst the peaks c,d, and a are only present in functionalised PDMS macromonomer.

[00264] FIG. 5 shows ¹ H NMR of PDMS macromonomer percentage functionality of both vinyl and ally PDMS macromonomer was calculated using the intergral of the peaks indicated

[00265] Taking into account the significantly lower %Fn, yield and two distinct populations of macromonomer being produced at this stage when using vinyl chloroformate as the functionalising reagent this PDMS macromonomer was not taken into the next step for building the copolymer library as the allyl-PDMS macromonomer would be more appropriate at this stage. [00266] FIG. 6 shows the MALDI-TOF mass spectra of functionalised PDMS macromonomer by Allyl Chloroformate.

[00267] The MALDI-TOF mass spectroscopy spectrum of the each PDMS macromonomer shown in FIG. 6, shows two distributions for macromonomers; one with the desired end group and the other with a hydroxyl end group. The difference between two main peaks is 74 m/z and confirms the presence of -Si-O- repeat unit. FIG. 6 also shows that the macromonomer is present in trivalent form as three peaks separated are by 222 mass units, which is the mass of monomer. The distribution pattern is the same across the spectra.

[00268] ATR-FTIR (Attenuated total reflectance Fourier transform infrared spectroscopy) has been performed on the resulting three PDMS macromonomers.

[00269] FIG. 7 show the ATR-FTIR traces for the Low Mw PDMS co-polymer (1 a from Table 3), Medium Mw PDMS co-polymer (2a from Table 3) and High Mw PDMS copolymer (3a from Table 3).

[00270] The IR spectra is as to be expected showing peaks which correspond to the target PDMS macromonomer with a very similar overlap in spectra seen for all macromonomers tested.

Example 2 - Formation of Silicone-based Amphiphilic co-polymer

Scheme 2 - Polymerisation to form amphiphilic co-polymer [00271] N-vinylpyrrolidone (NVP), PDMS allyl-functionalised macro-monomer, ACVA and tetrahydrofuran were mixed together in the desired ratio until the solid initiator had dissolved. The resulting solution was pipetted into a 100ml ampule and placed on a high vacuum line. The solution was then frozen with liquid nitrogen and vacuum was applied until a steady vacuum was achieved (3x10 ³ mBar typically) and then closed. The ampule was defrosted with tepid water, once thawed this process repeated until the ampule was completely degassed. The ampule was sealed using gas/oxygen blowtorch and placed in a water bath at 60°C for up to 24hrs to undergo polymerisation. The ampule was opened by cracking and the product was removed via pipetting. The solvent was evaporated by rotary evaporation under reduced pressure and the product was precipitated and repeatedly washed with diethyl ether. This was removed by vacuum filtration obtaining a white powder which was vacuum dried for 24hrs. The resulting NVP-PDMS copolymers were then characterized by Ή NMR,¹³C NMR, SEC, TGA, DSC, Elemental analysis, ICP- MS

[00272] ¹H NMR (400MHz, CDCI₃) δ/ppm: 0.15 (s, 3H, -CH₃), 1 .24 (br, 3H, -CH₃), 1 .25 (br,CH₂CH₂), 1 .9 (br, 2H, -NC(=0)CH₂CH₂CH₂)2.2 (br, 2H, -NC(=0)CH₂CH₂CH₂), 3.2 (br, 2H, -NC(=0)CH₂CH₂CH₂) 3.76 (q, 1 H, -NCH-)

[00273] ¹³C NMR (400MHz, D₂0, CPD) δ/ppm: 1 (1 C, CH₃Si-R), 18 (1 C, - CH₂CH₂CH₂C(=0)N-), 30 (1 C, -CH₂CH₂CH₂C(=0)N-), 41 (1 C, -CH₂CHN-) 43 (1 C, - CH₂CHN-),44 (1 C, -CH₂CH₂CH₂C(=0)N-), 176 (1 C, -N(C=0)CH₂-)

PDMS NVP Copolymer library

[00274] The PDMS-NVP copolymers were produced following Scheme 2 and the associated procedure above. The intention was to produce a library of copolymers of different weights using the Low, medium and high M_w macromonomers. However, as well as this within each weight group of copolymer there is three different molar feed ratios of PDMS: NVP being used 3:1 , 1 :1 and 1 :3 respectively (that is the molar content of monomers in a PDMS polymer relative to the the moles of NVP monomer fed into the respective polymerisation reactions). The results of the SEC analysis and yield of each copolymerisation is summarised below in Table 3.

Table 3 - SEC analysis of amphiphilic co-polymer library

1 :3 2a 122,800 77,700 1 .6 40

1 :1 MediumMwPDMS 2b 130,000 83,000 1 .6 45

3:1 2c 107,200 68,500 1 .6 40

[00275] The molar feeds for the polymerisation reactions do not however determine the resulting molar ratios of respective PDMS/PVP monomeric units in the resulting copolymer itself. To establish the actual monomeric molar ratios for PDMS and PVP portions of the co-polymers, firstly elemental analysis was performed to determine nitrogen content and then ICP-MS was performed to determine the silicone content present. The results are summarised below in Table 4.

Table 4 - Analysis showing molar ratio of monomeric ratios in both the polymerisation feed and the resulting co-polymers for the co-polymers listed in Table 3

[00276] As you can be seen from Table 4 the molar feed ratio and ratio present in the copolymers differ significantly, perhaps explaining some of the discrepencies in the later particle sizing experiments (see below). Furthermore, certain difficulties encountered when trying to dissolve these co-polymers in hexamethyldisiloxane are also explained by underesteimates of the degree of NVP polymer being ultimately incorporated within the co-polymer.

[00277] FIG. 8 shows a typical ¹ H NMR spectrum for a graft coploymer. The broad peaks present are indicative of poly N-vinylpyrrolidone ATR-FTIR

[00278] Attenuated total reflectance Fourier transform infrared spectroscopy has been performed on the resulting nine PDMS-NVP-graft copolymers.

[00279] FIG. 9 shows the ATR-FTIR spectrum for the Low Mw PDMS co-polymers (1 a- c from Table 3).

[00280] FIG 10 shows a comparison between the change in absorption between PDMS macromonomer and PDMS-NVP-graft copolymer 1 a.

[00281] FIG. 11 shows the ATR-FTIR spectrum for the Low Mw PDMS co-polymers (2a-c from Table 3).

[00282] FIG 12 shows a comparison between the change in absorption between PDMS macromonomer and PDMS-NVP-graft copolymer 2a.

[00283] FIG. 13 shows the ATR-FTIR spectrum for the Low Mw PDMS co-polymers (3a-c from Table 3).

[00284] FIG 14 shows a comparison between the change in absorption between PDMS macromonomer and PDMS-NVP-graft copolymer 3a.

[00285] The IR spectra of three copolymers made from each one of the three PDMS macromonomers (low, medium and high) show very similar spectra. However, the spectra is as to be expected much noisier for the PDMS-NVP-graft copolymers, due to lots more functional groups being introduced. The broad OH peak present in these spectra is most likely due to the hydroscopic nature of the PVP component of the copolymer. The main difference between the spectra is the appearance of a peak at 1600cm ¹ which could be due to the aromatic Pyrrolidine or the ketone.

Gel permeation elution chromatography (GPEC)

[00286] All gel permeation elution chromatography experiments were performed by addition of 20mg of substrate to the solvent in which they would not dissolve and the favourable solvent was added drop wise until the mixture went cloudy so that upon addition to the system the substrate would precipitate onto the column. The reference homopolymers used were PVP obtained from Aldrich with an average M_w of 20,000 and PDMS macromonomers used to synthesise each of the copolymers.

Normal phase [00287] The gradient performed was as follows; Hexane 100% for 4minutes, up to 20% IPA over next 2minutes then hold for 4minutes, up to 40% IPA over next 2minutes and hold for 4minutes then increase the gradient to 100% IPA over the next 5minutes.

[00288] FIG. 15 shows the normal phase chromatogram of Low MW PDMS 1 a-1 c showing the retention time (minutes) against response in mV. With the references shown in black (PVP) and grey (PDMS macromonomer).

[00289] The reference for PVP in FIG. 15(1 -3minutes) shows firstly that there is a large degree of homopolymer PVP in the reaction mixture, secondly it shows that there is a slightly different composition for 1 a-1 c with a peak occurring before the PVP reference. This could be due to the reaction producing a short homopolymer of PVP or a graft copolymer with most repeat units being NVP, either of these would explain the slight drift in response time from the reference PVP. The reaction has also unreacted PDMS macromonomer present shown between 12-16 minutes. The section between 8 and 10 minutes has been enlarged for better visualisation of the copolymer peak. The copolymers all elute at roughly the same time point as expected due to their amphiphilic nature. The relatively low amount of graft copolymer is due to the reactivity ratios between NVP and the allyl PDMS macromonomers, the large degree of homopolymer however is not a concern as this will allow for loading of Iodine to create PVP-I in situ within the PDMS adhesive membrane allowing for a more stable composition. The averaged amount of copolymer present from both normal and reverse phase using the area under the curve is tabulated in Table 5.

Reverse Phase

[00290] The gradient performed was as follows; IPA 100% for 4minutes, up to 20% Hexane over next 2minutes then hold for 4minutes, up to 40% Hexane over next 2minutes and hold for 4minutes then increase the gradient to 100% Hexane over the next 5minutes

[00291] FIG. 16 shows the reverse phase chromatogram of Low MW PDMS 1 a-1 c showing the retention time (minutes) against response in mV. With the references shown in black (PVP) and grey (PDMS macromonomer).

[00292] The noticeable difference between normal, FIG. 15, and the reverse, FIG. 16, phase runs is the separation of copolymer peaks. Whilst in the normal phase they elute at roughly the same time, however, there is a larger degree in separation when using reverse phase. The same can be seen for both runs; the assumed homopolymers of PDMS and PVP roughly elute at the same time. The slight difference in elution time has been previously discussed.

Table 5 - Average graft copolymer amount obtained from the area under the peaks for both normal phase and reverse phase runs.

TGA analysis

[00293] TGA was performed initially to determine at which temperature range would be appropriate to use for DSC analysis before polymer degradation started to occur. All samples were run from a 25°C TO 300°C at a rate of 10°C per minute. In FIG. 17 it can be seen that there is an initial loss in weight between 100 and 200°C this is thought to be water loss of the sample, which is to be expected as the copolymers contains a large degree of NVP which is highly hygroscopic. The chance that this is organic solvent is low due to 48hrs drying a vacuum oven at 40°C prior to DSC analysis. However, this could be short chain macromonomer being lost or short chain homopolymer of either PDMS or NVP. The polymer started to degrade at approximately 225°C and rapidly decomposed above temperatures of 250°C. Table 6 - refined molar ratio calculations in view of TGA analysis

[00294] FIG. 17 shows the TGA (thermogravimetric analysis) of a typical copolymer sample showing %weight loss over an increasing temperature range at a rate of 10 degrees per minute.

[00295] All copolymers regardless of NVP content have a similar degree to hold H₂0 with the total range being from 4 to 10 percent. This is perhaps unexpected, since one would expect a higher NVP content to allow for more water encapsulation. The bigger the PDMS component the more this would hinder the uptake of H₂0 - this general trend can be seen.

DSC analysis

[00296] A Perkin Elmer DSC pyris 1 was used, with Pyris manager 1 1 .1 software being used to collate data.

[00297] DSC was performed using a temperature range from -80 °C to 100°C at a rate of 10 degrees per minute, performing two heating cycles and one cooling cycle between on each sample. The first heating cycle of lowMw 1 a is shown in FIG. 18 (left), from this it can be seen that there is two T_g being observed (50°C, 63°C) which is due to the two components PDMS and NVP being present and phase separated initially. However, on the second heating cycle there is only one T_g recorded (71 °C) which is due to the individual components now being phase mixed resulting in only one T_g present. The cooling cycle shows an endothalpic spike which may be due to the sample forming a crystalline structure.

[00298] FIG. 18 shows a DSC of a LowM_w1 a showing (a) the first heating cycle in red and cooling shown in blue, (b) is the second heating cycle again shown in red with only one T_g being present. [00299] DSC was performed on the entire copolymer library and is summarised below in the graph of FIG. 19 and Table 7 below.

Table 7 - Showing the DSC analysis for all of the co-polymers in the library of Table 3.

[00300] FIG. 19 shows the DSC for each copolymer sample set showing the trend between samples of roughly the same weight differing in PDMS NVP molar ratios and between sets of varying PDMS macromonomer size.

[00301] As can be seen from FIG. 19, the larger the PDMS macromonomer the larger the Tg between sample groups. Within the sample groups it can be seen that the larger degree of NVP component the larger the Tg again. This can due to the increase in size as the increase in ratio of NVP means also that the size of the copolymer is also increased.

Example 3 - Formation of Particles of Silicone-based Amphiphilic co-polymer

[00302] Particle size analysis was carried out on a Brookhaven Instruments Corporation ZetaPALS Zeta Potential Analyser with the 90Plus/BI-MAS Multi Angle Particle Sizing Option. Samples were prepared at 0.5 % concentration (5 mgml ¹) by either dissolving directly in the required solvent or by using the solvent switch method.

[00303] Measurements were made at 25 °C unless otherwise stated. 10 analysis runs were made in triplicate for each sample.

[00304] In aqueous solution the following procedure was followed; 10mg of copolymer (this procedure was the same for each copolymer 1 a-3c) was added to 2ml_ of Ultra pure H₂0 and left to shake for 1 hour prior to use. A cuvette was filled with 2ml_ of 10mmol KCI solution to which 300μΙ_ of copolymer solution was added. This final solution was used for particle size analysis. For particle sizing in organic solution the following procedure was used; 10mg of copolymer was added to DCM and stirred for 1 hour prior to use 200μΙ_ of this solution was added to cuvette containing 2ml_ of DCM.

Particle sizing - Aqueous solution

[00305] FIG. 20 shows a graph that shows as the NVP ratio is increased within the copolymer the general trend is that as too be expected the size of these particles decrease. Interestingly the PDMS component of the copolymer doesn't seem to have an effect on the size of the particulates formed.

Particle sizing - Organic Solution

[00306] FIG. 21 shows a graph that shows as the NVP ratio is increased within the copolymer the general trend is that as too be expected the size of these particles. The increase shown is due to the interaction of the hydrophilic component and the hydrophobic solvent. Interestingly the PDMS component of the copolymer doesn't seem to have an effect on the size of the particulates formed, with an outlier being seen in the medium PDMS which does not fit this trend. However it is worth noting that this point also has the largest error associated with it and will be repeated as a result.

Transmission electron miscroscopy (TEM)

[00307] Sodium periodate (4 g) was dissolved in deionized water (100 ml, 25°C) and chilled. RuO₂-xH₂0 (0.6 g) was added to the aqueous Nal0₄ solution. All of the black ruthenium dioxide powder dissolved, producing a stable yellow solution of Ru0₄.

[00308] This yellow solution is then poured into the bottom of a sealable container and the parafilm with the grids on is balanced above the solution (typically 1 1 μΙ of the desired sample having been allowed to dry on the grids previous to this). The container is then sealed and the fumes allowed to deposit the ruthenium onto the grids for 7 minutes.

[00309] TEM imaging was carried out using a Philips CM 100 instrument operating at 100 kV. Polymer samples dispersed in ultrapure H₂0, or ethanol where stated, were prepared for TEM by adsorbing a 5 μΙ drop of sample onto a glow-discharged carbon- coated grid for 1 minute. The grid was blotted, washed in a drop of distilled water and blotted again. The grid was then washed in a drop of uranyl formate, blotted and then negatively stained by holding the grid in a drop of uranyl formate for 20 seconds before blotting. [00310] FIG. 22 shows the TEM images of graft copolymers stained with ruthenium, for a) Low Mw PDMS co-polymer (1 a from Table 3) b) Medium Mw PDMS co-polymer (2a from Table 3) and c) High Mw PDMS co-polymer (3a from Table 3).

[00311] From FIG. 22 it can be seen is that all of the graft copolymer compositions (1 a, 2a and 3a) form what to appear micelles of varying size. The sizes of the micelles are consistent with the particle size measurements (FIG. 20), with the average particle sizes being between 500nm to 1000nm

[00312] FIG. 23 shows enlarged areas of the TEM images showing micelle micro structure for a) Low Mw PDMS co-polymer (1 a from Table 3) b) Medium Mw PDMS co- polymer (2a from Table 3) and c) High Mw PDMS co-polymer (3a from Table 3).

Example 4 - Absorption of Hydrophilic Agents by Silicone-based Amphiphilic copolymer Particles

Encapsulation of HpO inside copolymer micelles in organic solvent

[00313] 10mg of each copolymer (this procedure was the same for each copolymer 1 a- 3c) was dissolved in 10ml of DCM, once dissolved 1 .1 ml of H₂0 was added drowse to the stirring solution. A control of DCM alone was also done with the addition of 400uL of H₂0 causing a visible phase separation whilst the DCM containing the solution had a maximum load of 1 .1 mL H₂0 before this occurred. This is a 10 wet weight percent uptake, knowing this the samples were left to rest and using a light microscope pictures were taken at 0, 4, 8, 24 and 48hrs at 10, 20 and 40x magnification to determine stability and/or changes in physical morphologies of these apparent swollen micelles.

[00314] FIG. 24 shows light microscope pictures taken for the Low Mw PDMS copolymer (1 a from Table 3) at 0, 4, 8, 24 and 48hrs at 10, 20 and 40x magnification to determine stability and/or changes in physical morphologies of these apparent swollen micelles.

[00315] FIG. 25 shows light microscope pictures taken for the Medium Mw PDMS co- polymer (2a from Table 3) at 0, 4, 8, 24 and 48hrs at 10, 20 and 40x magnification to determine stability and/or changes in physical morphologies of these apparent swollen micelles.

[00316] FIG. 26 shows light microscope pictures taken for the High Mw PDMS copolymer (3a from Table 3) at 0, 4, 8, 24 and 48hrs at 10, 20 and 40x magnification to determine stability and/or changes in physical morphologies of these apparent swollen micelles.

[00317] Determining the change in morphology/stability of these micelles is difficult using light microscopy alone it would seem that the there are indeed larger micelles forming retaining large amounts of water which slowly disappear over time. However, even after 48hrs none of the water is released from these micelles as no phase separation occurs or at least not 400μΙ as this would cause a visible phase separation seen in the control. This would suggest these initial larger micelles are unstable and break down too much smaller micelles but creating a much larger degree of micelles within the solution which can be seen to aggregate to increase stability. This could be due to the gain in stability and also that due to the increase in number the likelihood of this occurring has also increased.

Example 5 - Formation of Test Wound Dressing Compositions and Wound

Dressing membranes

PDMS Membrane

[00318] The PDMS membrane was prepared by adding 'x' amount of Rhodamine B (see Table 8) dissolved in an x amount of water (see Table 8) to a swirling copolymer solution (co-polymer 1 a) containing an 'x' amount of hexamethyldisiloxane (see Table 8). This was then added to 5g of component A of the PDMS membrane and stirred whilst adding 5g of component B (provided by Scappa healthcare™ and commercially sourced as SILPURAN® 21 10 A/B Silicone Gel, which is commercially available from Wacker Chemie AG). Once both components had been added the viscous dispersion was drawn down using a K bar of 150μηι and left in an oven at 60°C for 10minutes to cure. The exact amounts of Rhodamine B, copolymer, and associated solvents are given in Table 8 below to yield 0.1 , 0.15, 0.20, 0.5, 1 and 10% copolymer blended PDMS membranes.

Table 8 - Details of amounts and ratios of components used to form a variety of PDMS membranes

[00319] Table 8 below provides a consolidated version of the data presented in Table 8, which shows relative wt% and wt ratios of the respective components. Table 9 - Consolidated version of Table 8 (condensinq entries a, b, c into a sinqle entry)

[00320] Of the above entries in Table 9, mixture number 5 appeared to provide the most promising composition for use in wound dressings.

Example 6 - Testing of Wound Dressing Compositions and Wound Dressing membranes SEM images of membrane

[00321] Membranes were applied to an aluminium stub (0.5 inch diameter) using a carbonised sticky tab as an adhesive. The stub(s) were coated with gold using and Edwards S150b coater and viewed using a Philips XL-20 SEM at 20Kv.

[00322] FIG. 27 shows SEM images of three different membranes, where the membranes respectively contained 0, 1 and 10% copolymer (i.e. the weight ratio of copolymer to PDMS matrix material was 0, 1 :100 and 1 :10 respectively), shown from left to right. This is due to them being the most varied in the sample range. As the copolymer content is increased from zero to 10% the surface morphology changes from being smooth to becoming much rougher with increasing populations of 'pimples' appearing on the surface. This is most likely due the particles observed in solution protruding from the surface. 10 percent peel test

[00323] FIG. 28 shows SEM images following a peel test of the SEM "stubs" of FIG. 27. The peel test was one which only worked for the 10% copolymer this is most likely because of the large amount of copolymer micelles present on the surface of this membranes when compared to the 1 % copolymer membrane. The peel test was conducted simply by taking the 'stub' used for SEM imaging to which the SEM imaging is typically done, and imprinting this onto the membrane.

[00324] The rather interesting results you can see from the SEM images taken (FIG. 28) is that the micelles formed on the surface shown on the left are only loosely embedded into the membrane and upon peeling the SEM 'stub' you can see that they stay intact and can clearly be seen as micelles shown on the right. These results also suggest that the PDMS membrane at 10% composition is not completely set, unlike the other membranes at lower concentrations of copolymers. Confocal microscopy

[00325] Images (512 x 512 x 182) were obtained using a Zeiss LSM 10Meta inverted confocal microscope and EC Plan-Neofluar 40x/1 .30 oil DIC, with a pixel dwell time of Ι .θΐ με. Rhodamine B was excited using a 543 nm laser (31 % transmission). All image analysis was performed using Zeiss LSM Image Browser.

[00326] Confocal microscopy images were taken of the 0.1 , 1 and 10% copolymer membranes. The ratio of Rhodamine B/copolymer is either 1 :5 or 1 :2.5. These images were then Z-stacked to produce a projected image side on, shown in FIG. 29 (magnification x16). The software used to reconstruct these images was LSM image browser.

[00327] FIG. 29 shows confocal images of three membranes all Z stacked using LSM image browser, (a); 0.1 % copolymer with elongated spheres roughly ranging from 5-15μηι in length and 5μηι in width, (b); 1% copolymer showing large elongated spheres showing a large range of sizes from 5 up to 50μηι. (c); 10% copolymer showing a diffuse layer of copolymer and rhodamine B throughout the entire membrane.

[00328] From FIG. 29 it is clear to see that Rhodamine B has been encapsulated within the membrane suggesting that the hydrophilic molecule in this case Rhodamine B is being held within copolymer micelles. It is remarkable just how much Rhodamine B has been incorporated into the membrane. This is clear to see with the 1 % copolymer image (FIG. 29(b): middle) showing concentrated regions of Rhodamine B up to 50μηι in length and up to 20μηι across. Particle sizing analysis of copolymers yielded micelles with the largest size in diameter of 10μηι, suggesting these micelles seen with the Rhodamine B incorporated can aggregate together to form much larger micelles which can also be seen to occur when visualising these micelles swollen with H₂0 under a light microscope. The 10% copolymer membrane (FIG. 29(c); bottom) showed a much thinner than expected red 'smear'. This would initially suggest that the Rhodamine B is diffuse entirely throughout the membrane however, that the cross linking process of the PDMS matrix is severely hampered by the shear amount of solvents, copolymer and Rhodamine B present in the matrix, resulting in the formation of a highly viscous solution being formed not a membrane. This is also backed up with the images from the SEM peel test conducted on the 10% copolymer, showing material, possibly micelles being easily removed and images alone.

Copolvmerisation with Fluorescein o-acrylate

[00329] PDMS functionalised macromonomers was reacted with N-vinylpyrrolidone in the same method as explained above, with the addition of 1 wt% of fluorescein o-acrylate added to the reaction mixture

[00330] Upon copolymerisation with fluorescein o-acrylate the copolymer location in relation to Rhodamine B was discernible.

[00331] FIG. 30 shows the confocal images for copolymer (LowMWPDMSI a) containing fluorescein o-acrylate dissolved in H₂0 at 5mg/ml concentration, wherein in the top left the confocal image for just fluorescein o-acrylate is displayed, in the top right the confocal image for just Rhodamine B is displayed, and at the bottom the overlaid images are displayed, wherein the yellow is a result of the combination of both green and red fluorescence.

[00332] FIG. 31 shows the confocal images for copolymer (LowMWPDMS 1 a) containing fluorescein o-acrylate dissolved in hexamethyldisolxane at 5mg/ml concentration, wherein in the top left the confocal image for just fluorescein o-acrylate is displayed, in the top right the confocal image for just Rhodamine B is displayed, and at the bottom the overlaid images are displayed, wherein the yellow is a result of the combination of both green and red fluorescence.

[00333] The images in FIGs 30 and 31 show the copolymer forms micelles in hydrophobic solvent and not in H₂0.

Contact angle measurements

[00334] Contact angles were measured using a Rame-Hart goniometer by the sessile drop method. The sample stage was made level using a bulls-eye level; the sample was then placed on the stage. A water droplet (2 μΙ) was formed on the surface with a microliter syringe. The angle of the liquid-solid-gas/vapour interface was measure. Multiple measurements were taken for each sample in separate areas of the sample and the average value recorded.

[00335] Contact angle measurements where conducted using a goniometer, microscope and a pipette containing ultra pure H₂0 and 1 -Bromonaphthalene. Measurements were taken in repeats of five with the results being shown below in FIGs 32a and 32b.

[00336] FIG. 32 is a graph showing the contact angles as a dependency of % copolymer present within the membrane in a) H₂0 and b) 1 -Bromonaphthalene.

[00337] The trend which can be seen is to be as expected - i.e. the larger the amount of copolymer (i.e. which increases overall hydrophilic content), and the higher the NVP content (which again increases overall hydrophilic content), the more likely the hydrophilic PVP polymeric component will be present at the surface. The more hydrophilic a surface becomes, the lower the contact angles will be.

[00338] For the same reason the contact angle increases when using 1 - Bromonaphthalene as this is a non-polar hydrophobic solvent. [00339] Using the contact angles obtained it is possible to determine the polar and the non-polar dispersive components of the surface energy of a solid using Fowkes equation. Using this equation the adhesion energy is a sum of two partial contributions, each of which is expressed as the geometric mean of two adhesion parameters, γι_ and ys, the first of which characterizes the "adhesive power" of the liquid, and the second, of the solid. (l + cos Θ) = 2[JAY^ds +

Equation 1 y^DL - Dispersion forces surface energy of the liquids y^ds - Dispersion forces surface energy of the solid

Y^PL - Polar interaction surface energy of the liquids

y^ps - Polar interaction surface energy of the solid

[00340] The adhesion parameters of the liquids are known (Table 10). Therefore, by measuring the contact angles for two different liquids, the remaining two parameters, those of the solid can be found.

Table 10 - The surface energy of two liquids used; H₂Q and 1 -Bromonapthalene and the two components dispersion forces and polar interactions.

[00341] Using 1 -Bromonapthalene allows for the equation to be simplified and solved as the polar component (γι_^ρ) is zero. As a result the total surface energy and % polarity of the surface can be calculated, which is shown below in Tabe 1 1 for low MW PDMS 1 a.

Table 1 1 - Total surface energy and % polarity for Low MW PDMS 1 a at copolymer concentrations of 0.1 , 0.5, 1 , 2.5, 5 and 10% with the dispersion and polar components shown.

I 5 9.66 0.83 10.49 7.90

I 10 10.99 9.42 20.41 46.14

[00342] What can be seen by addition of more copolymer to the PDMS membrane is the surface energy decreases. As surface energy is an adhesive parameter this lowering in energy means a decrease in energy gained upon bringing the surface into contact with other materials. The result of this is that the membrane essentially becomes less 'tacky' as a material. The % polarity of the surface increases as to be expected with the increased amount of % copolymer present; the surface is becoming more polar.

Peel adhesion testing

[00343] A Housefield Tensionometer was used with a 5 Newton load cell to conduct all peel tests. The test conditions were as follows for all tested materials; 19°C, 55% humidity, 25mm width, 225mm peel length at a speed of 300mm/min with a start tension of 0.08N, with polycarbonate being used as the stationary phase. All data was recorded and analysed with QMat professional 5 series.

[00344] Membranes were loaded in the same concentrations as shown in Table 7 excluding Rhodamine B.

[00345] FIG. 33 shows the peel adhesion results for a) Low Mw PDMS co-polymers (1 a-c from Table 3) b) Medium Mw PDMS co-polymers (2a-c from Table 3) and c) High Mw PDMS co-polymers (3a-c from Table 3). All membranes were 25 mm in width with a peel length of 225 mm and were peeled at a rate of 300 mm/min with a start tension of 0.08 N with polycarbonate being used as the stationary phase. The reference region is shown between the two black dotted lines, this region is peel adhesions conducted under the same conditions but with silicone only gels made under the typical industry conditions (120 °C) and the conditions used to make the doped silicone gels (70 °C).

[00346] The reference region between the black lines is typically between 1 .6 N and 2.9 N and is generally considered to be the 'ideal' region for industrial application. Two silicone only reference gels were made by adding equal amounts of component A and B (SILPURAN 21 10 A and SILPURAN 21 10 B respectively) as done previously. However, the temperature and time of curing differs between the two, with the industry silicone gel reference being set at 120 °C for two minutes and the other being 70 °C for 15 minutes. The reason the setting procedure differs between the two reference gels is that for the doped silicone adhesive membranes contain H₂0, meaning the higher temperature causes the water to evaporate leaving behind an un even surface not suitable for application so a lower temperature and longer curing time has been used.

[00347] FIG. 33 shows that the copolymer concentration for 1 a-1 c does not seem to affect peel adhesion with the majority lying in the 'ideal' region. The same cannot be said with 2a-2c with the general trend that increasing the concentration decreasing the peel adhesion with only about half the membranes falling within the 'ideal' region. This is what you would expect as the polycarbonate is a hydrophobic surface with a low surface energy as a direct result the increase in copolymer presence at the surface would decrease the adhesion between the two surfaces. The final copolymers 3a-3c peel adhesion results stay relatively consistent across the concentration range with all lying below the 'ideal' region. Comparing the peel adhesion between groups it can be said that as the increase in molecular size of the copolymer present in the membrane has as detrimental effect on the adhesion. This may be due to the probability of hydrophilic regions being present at the surface as the size of the copolymers and resulting micelles increase.

Moisture vapour transfer rates (MVTR)

[00348] The flange of a paddington cup was used as a template and three repeats of each test sample were cut. The base of three paddington cups were clamped together and 20ml of deionised water added to each cup (sufficient to leave an air gap of 5mm between the liquid surface and the dressing sample). The samples were then clamped onto the paddington cups to ensure a water tight seal. Samples were then weighed and placed in an oven for 3hours at 37 ^°C, samples were then weighed to calculate weight loss. This data was then extrapolated to gain gnr²24hr¹ of water.

[00349] FIG. 34 shows the gnr²24hr¹ of water loss for a) Low Mw PDMS co-polymers (1 a-c from Table 3) b) Medium Mw PDMS co-polymers (2a-c from Table 3) and c) High Mw PDMS co-polymers (3a-c from Table 3).

[00350] From FIG. 34 it can be seen that MVTR rates increase with the amount of copolymer within the membrane, with 1 a-1 c showing the highest extrapolated MVTR. Interestingly, it can be seen from FIG. 34 that the amount of moisture transferred (MVTR) from any PDMS membrane containing 2.5% of copolymer increases three fold.

[00351] This is an important property as one of the drawbacks of using silicone adhesives as a wound contact layer is that the material has to be post modified via perforation to allow for fluid to flow from the wound into an absorbent foam. Rhodamine B release experiments

[00352] The different PDMS membranes containing the various concentrations of copolymer and Rhodamine B were placed in 2ml_ of phosphate buffer solution (PBS) in tissue culture plastic and analysed at 0, 0.5, 1 .5, 4, 24 and 48hr time periods using a specord S600 with the wavelength of 500 - 600nm being the region of greatest absorption for Rhodamine B.

[00353] FIG. 35 shows the release profile of rhodamine B from the membranes at 0, 0.5, 1 .5, 4, 24, 48hr time periods ranging from 0.1 % to 10% copolymer concentrations, as measured using a specord S600 spectroscope with the wavelength of 500 - 600nm. The following lines correspond with the following measurement times Black (Ohr), Red (0.5hr), Orange (1 .5hr), Green (4hr), Blue (24hr), Purple (48hr).

[00354] Please note that the release profiles shown in FIG. 35 are distorted at Ohr, where all membranes initially seem to release more than would be expected, because the membranes were not washed prior to being submerged in PBS, thus some rhodamine B would be only loosely attached to the surface. However the absorption then decreases again after this affect has subsided. The picture is quite complex due to the complex dynamics involved in these experiments. However, the rhodamine B is slowly released up until about 4hours in each case before the rhodamine B begins to adsorb to the tissue culture plastic at around 48hr release being the lowest absorption seen in each membrane. The one exception to this pattern is the 10% copolymer, no doubt for the reasons discussed previously that this membrane is insufficiently 'crosslinked' and thus dissolves in the PBS over time. The problems which have been observed in this experiment have been rectified with the tissue culture plastic being replaced with glass sample tubes to prevent adsorption and at 37°C to more closely mimic that of a wound site.

7 day release experiment in glass

[00355] This experiment was carried out as detailied in the previous experiment (above) in terms of detection. However, the samples were now placed in 5ml of PBS and placed in 10ml sealed glass sample tubes and placed in an oven set to 37°C. The results were obtained from making the membranes in triplicate and taking 3 repeat readings of each triplicate membrane, the results are shown in FIG. 36.

[00356] FIG. 36 shows the 7 day release profiles of 0.1 , 0.5, 1 , 2.5, 5 and 10% copolymer (with the Rhodamine/copolymer ratios corresponding to those of Table 7) showing the general trend that as the amount of Rhodamine B is increased within the copolymer present in the membrane, the larger the absorption observed after 7 days. [00357] This release profile data is much more akin to what one would expect, with the observed absorption increasing with the increase of amount of rhodamine B present in the membranes. The 10% copolymer data is removed from this graph to avoid distortion of the graph.

72 hour time point release profile

[00358] This experiment was carried out as detailied in the previous experiment (above) in terms of detection. However, the samples were placed in 3 ml of PBS in 6 ml sealed glass sample tubes then transferred to an oven set to 37°C. The results were collected through making the membranes in triplicate and taking 3 repeat readings of each triplicate membrane as before, the results including standard error have been corrected to concentration using the beer Lambert law using the molar extinction coefficient of 101 ,000 molL¹.

[00359] FIG. 37 shows the 72 hour time point release profiles of 0.1 to 10 % membranes with scans taken at 551 nm at time intervals of 30 min for the first 4 hr and then every hour until 12 hr. he remaining time points were taken at 16, 24, 36, 48, 60 and 72 hr.

[00360] Interestingly from FIG. 37 the results are as predicted, showing a stable release for all concentrations except 10% which depicts a burst release indicative of a non- set membrane for reasons discussed previously. However, there is a definite 'sweet' spot where adding more copolymer and Rhodamine B does not equate to more being released as shown for the 1 and 2.5 %; unexpectedly a larger amount is released from 1 %. This is ideal from a manufacturing point of view where 'less is more'.

[00361] The results obtained in FIG. 37 can be applied to Fickian's second law of diffusion. Peppas (Eur.J. Pharm. Biopharm. 50 (2000) 27-46) suggests using a power relationship between release rate and Fickian's second law of diffusion of a diffusate from a hydrogel shown in Equation 2.

Equation 2

[00362] Equation 2 can only be applied to 60% of the total amount of drug released otherwise Fickian's second law of diffusion does not hold. Here, I and M^™ are the amounts of drug released at time (t) and at equilibrium, respectively. K is a proportionality constant, and n is the diffusional exponent. The value of the exponent is very informative with values of between 0.5 being normal non-hindered diffusion. Values below 0.5 indicate a restriction of diffusion whether this is chemically or structurally.

[00363] FIG. 38 shows the fraction of Rhodamine B released against time below 60% of maximum release to obtain power exponent 'η' of 0.1 -5% copolymer composition, as tabulated in Table 12.

Table 12 - the power exponent 'n' values calculated for the fraction of Rhodamine B released against time below 60% of maximum release for 0.1 -5% copolymer compositions.

[00364] From Table 12 it can be seen that the values fall between 0.5 and 1 which is what is expected for this system, where the release is non-hindered and should be diffusion based.

48hr time point release profile of Rhodamine B

[00365] FIG. 39 shows the Rhodamine release for all copolymer compositions (1 a-3c) monitored over 48hs and at various concentrations (0.1 , 0.5, 1 , 2.5 and 5%).

[00366] From FIG. 39 it can be seen that, in general, as you increase the amount of Rhodamin B within the composition there is an increase in maximum amount released. However, the increment in increase varies between copolymers, with Low MW PDMS 1 a being the most uniform. Medium MW PDMS 2a 0.1 % Rhodamine B was shown not to release at all over the 48hr time period. High MW PDMS 3b 5% Rhodamine B released the largest concentration of Rhodamine B out of all compositions presented. The Fickian constants for all of the compositions presented above have also been calculated in tangent with the maximum release and is presented in FIG. 40.

[00367] FIG. 40 shows that the rate of release various depending on copolymer composition and amount of Rhodamine B. There can be two interesting things that can be speculated from this. Firstly, that each copolymer composition effects the PDMS membrane morphology and secondly that the amount of Rhodamine B present further effects the morphology. Ideally in a system with the intended use of drug delivery to human infected wounds you would want the Fickian constant to be at a value of 0.5 (rate of diffusion) and above. The data suggests that a large degree of copolymer compositions at various loading concentrations are capable of achieving this.

Example 7 - Antimicrobial rlease and cytotoxicity studies

Silver release studies

[00368] 3 by 3cm² squares of silver containing PDMS membranes were added to 5ml of ddH₂0 and incubated at 37°C for 48hrs. NaCI₂ was added to the solution causing the precipitation of Silver Chloride (AgCI), NaCI₂ was added until precipitate stopped forming. This precipitate is then filtered, dried, and it's mass determined. From the mass of the AgCI, the mass of Ag in the Solution can be determined.

[00369] Two studies were conducted, the first of which used the entire copolymer library using a 1 % Ag loading concentration.

[00370] FIG. 41 shows the silver release data for all membranes, loaded at a 1 % Ag concentration. Release was monitored via a gravimetric method with low PDMS MW 1 a, Medium PDMS MW 2a and High MW PDMS 3c releasing the maximum amount of Ag over a five day period.

[00371] The results shown in FIG. 41 were obtained with many repeats to reduce and/or remove error associated with the gravimetric method for monitoring the release.

[00372] From FIG. 41 it can be seen that Low MW PDMS 1 a, Medium MW PDMS 2a and High MW PDMS 3c releases the most silver.

[00373] Taking into account that the maximum release was obtained from Low MW PDMS 1 a, Medium MW PDMS 2a and High MW PDMS 3c and these were then taken forward and release was monitored with an increased amount of Ag to 2.5%.

[00374] FIG. 42 shows the silver release data for all membranes, loaded at a 2.5% Ag concentration. Release was monitored via a gravimetric method with low PDMS MW 1 a, eleasing the maximum amount of Ag over a five day period.

[00375] The results shown in FIG. 42 correspond with the release pattern shown previously in FIG. 41 with the maximum release achieved from low MW PDMS 1 a followed by medium MW PDMS 2a and high MW PDMS 3c. Corrected zone of inhibition (CZOI)

[00376] Under sterile conditions membrane samples were cut into 3 x 3cm² and a challenge lnoculum_was then prepared by Disperse representative colonies of the chosen challenge organism in Maximum Recovery Diluent (MRD) to achieve a specific optical density (OD550) equivalent to approximately 1 x10⁸ cfu/ml. The solution was then diluted 1 in 10 in MRD until to a final population concentration of approximately 1 x10⁶ cfu/ml was achieved. A total viable count (TVC) using the surface count method was then be performed to determine the number of viable organisms per millilitre Inoculation of test plates was performed using a sterile swab before addition to suspenison onto Wilkins- Chalgren Agar plates. Plates were then incubated for 4 hours in an appropriate atmosphere (37°C, 5% C0₂).

[00377] After the initial incubation, membrane samples were antiseptically transferred to the centre surface of an inoculated plate and press down lightly to ensure intimate contact with the agar. A negative control plate was also set up by placing a sample of gauze or the test sample without the antimicrobial in the centre of a previously inoculated plate. Plates were inoculated for a further 24hrs. CZOI was calculated as follows;

[00378] After digital callipers were used to determine the zones of inhibition. Four measurements were taken A, B, C and D, as shown in FIG 43.

[00379] The zone of inhibition (ZOI) is determined by multiplying A by C. With the dressing size being determined by multiplying B by D. The corrected zone of inhibition (cZOI) can then be determined by subtracting the dressing size from the ZOI as shown below in equation 3;

CZOI = (A x C) - (B x D)

Equation 3

[00380] Corrected zone inhibition studies were carried out for all three copolymer compositions. The wound dressing was applied and incubated over night at 37 °C for 24 hr. Following this the wound dressing was removed and pthe plates were re-incubated for another 24 hr at 37 °C. Finally, bacterial re-growth after 24 hr of incubation after wound dressing removal was examined. The results are summarised in FIGs 43-46.

[00381] FIG. 44 shows the corrected zone inhibition studies for the polymer composition low MW PDMS 1 a.

[00382] FIG. 45 shows the corrected zone inhibition studies for the polymer composition medium MW PDMS 2a. [00383] FIG. 46 shows the corrected zone inhibition studies for the polymer composition high MW PDMS 3c.

[00384] FIG. 47 shows the corrected zone inhibition studies for the control experiment, wherein no polymer composition was added.

[00385] What you can see from FIGs 43-46 is firstly that membranes without the presence of Ag do not prevent the growth but do indeed promote the growth of microbials. Secondly, you can see that the efficacy at least visually is 1 a, 2a and 3c respectively.

[00386] Comparing the control membranes containing Ag but no graft copolymer with those containing graft polymers shows that the controls do have some efficacy towards both species of bacteria. However, this is due to these membrane depositing clumps of Ag upon removal of the dressing before the 24hr re-incubation. These results, therefore, are not a true representation of the potential of these doped membranes to deliver antimicrobials to a wound, due to the release method being most optimal when in the presence of a wet surface or completely submerged within a liquid as shown with the use of Rhodamine B (described above).

Antimicrobial activity test

IS022196 standard protocol

[00387] Under aseptic conditions PDMS membrane samples were cut to 5 x 5cm² and transferred to a sterile Petri dish. 4 x 4cm² film samples were also cut and transferred to a sterile Petri dish so that every test sample has a film sample.

[00388] Challenge Inoculum was prepared by dispersing representative colonies of the chosen challenge organism in Tryptone Soya Broth (TSB) to achieve a specific optical density (OD550) equivalent to approximately 1 x10⁸ cfu/ml. This was then diluted to a final population concentration of approximately 6x10⁵ cfu/ml. A standard plate count (Ohr) was then performed on this suspension to determine the number of viable organisms per millilitre.

[00389] Test materials were then Inoculated via pipetting 400μΙ volume of the challenge organism (approximately 6x10⁵ cfu/ml) onto each test sample, then by placing a film sample on top of each test sample so that the liquid spreads across the surface of the test sample. Negative control were also prepared using non-antimicrobial sample. Test and control samples were then incubated at 35 °C {±3°C) for 24 hours. [00390] Total Viable Counts (TVC's) were then performed by firstly pipetting 10ml volumes of DE Neutralising Broth (DENB) into each test and control Petri dish. Secondly, microbial plate counts were made by making serial, ten-fold dilutions in DENB from the test/control Petri dish. Following this, 1 ml/100μΙ volumes were dispensed onto duplicate Tryptone Soya Agar (TSA). Inoculum was then spread using L shaped spreaders and plates were then incubated at 35°C (±3°C) for 48 hrs.

[00391] Antimicrobial activity of test samples was measured by the log reduction compared to that of the control samples.

[00392] Antimicrobial activity tests were only performed on Low MW PDMS 1 a, Medium MW PDMS 2a and High MW PDMS 3c. All tests were performed as stated in the IS022196 standard protocol above.

[00393] FIG. 48 shows the initial inoculation of bacteria on the left in black and control adjacent to this also in black with the test materials shown in red, green and blue. All materials were tested against both S. aureus and P. aeruginosa.

[00394] After initial inoculation the control sample which contains no copolymer or antimicrobial shows a 2 log increase in CFU which is to be expected and confirms that the bacteria used is proliferating normally. After incubation with the three test materials the proliferation of these bacteria is halted and the bacterium begin to die. However, this is not the case for High MW PDMS 3c which did not kill the bacteria but did reduce proliferation when compared to the control. This correlates with what was observed previously in the CZOI expriments (above). Graft copolymers Low MW PDMS 1 a and Medium MW PDMS 2a performed almost identically with a 'total kill' (>10¹ log CFU detected) of P. aeruginosa and a 3 log reduction observed when exposed to S. aureus. These results suggest that these systems deliver given antimicrobial in the presence of a liquid interface.

Culture of human epidermal fibroblasts (HDF)

Method

[00395] 60 mL of Dulbecco's modified Eagle's medium (DMEM) was removed from the 500 mL bottle, and replaced with 50 mL fetal bovine serum (FBS) and 10 mL penicillin- streptomycin. The bottle was agitated before 9 mL of complete medium was removed and placed in a T75 cell culture flask. This aliquot of medium was warmed in the incubator for 30 minutes, whilst the remaining media was stored in the fridge for up to six weeks. After 30 minutes the cryopreserved cells were gently agitated in a water bath at 37 °C for 1 minute, until the frozen plug' broke inside the vial. The cells were then quickly transferred to the pre-prepared T75 and gently swirled to thaw completely. The cells were kept in the incubator at 5% C02, 37 °C for 24 hours, in order to adhere, before a complete media change was performed. Complete media changes were then performed every 2-3 days, with daily checks of cell health using phase contrast microscopy.

Passage

[00396] Cells were passaged upon reaching 90% confluence by looking under microscopy. Old medium was removed from the flask and the cells were washed with 10 ml of sterile phosphate buffered saline (PBS). 5ml of trypsin was added to the cells and the flask was agitated very well at room temperature. Optical microscopy was used to observe the detachment of cells, and when 90% complete detachment observed 5 ml of trypsin neutralize solution was added to the flask. The entire contents of the flask were then added to a sterile centrifuge tube and spurn at 1500 rpm for 5 minutes. The supernatant was removed from the tube and the cells were re-suspended in a known amount of media. An appropriate amount of cell solution was then added to fresh, sterile T75 flasks and then serum-free media added to make a total 10 ml. the flasks were then placed in incubator at 37°C, 5% C0₂.

Cryopreservation

[00397] The CoolCell (Biocision) container was placed in a polystyrene container and surrounded with dry ice to cool down.

[00398] The cell freezing medium was prepared by adding 10% DMSO in FBS.

[00399] The cells were washed with sterile PBS and trypsin was added as described above in the passage protocol. After removal of the supernatant after centrifugation, the cells were resuspended in freezing medium and placed in a cryovial with a density of ~1 x10⁶ cells per ml. the cryovials were then promptly placed in the cooled CollCell (Biocision). After 24 hours the cryovials were removed and placed in canes within liquid nitrogen dewar at -196°C.

Thawing

[00400] Removed the cryovial from the liquid nitrogen container and thawd in water bath at (37°C) for 2 minutes. The cryovial was rinsed thoroughly with 70% ethanol under a laminar flow, then open the vial and transfer the cells to a cell culture flask that contain the prewarmed medium.

Cell counting [00401] Cell counts were performed by resuspending cells in a known volume of fibroblast culture media. 100μΙ of this cell solution and 100μΙ of the trypan blue stock solution were mixed to form a 1 :1 solution. 10μΙ of this solution was then withdrawn and placed into the chamber of the Neubauer haemocytometer. Non-viable cells are stained blue by the trypan blue. Cells were visualised using a phase contrast microscope and viable cells counted.

[00402] The concentration of viable cells was determined by Equation 4.

Cells / ml = n x 2 x m x 10000

Equation 4

wherein n = Number of viable cells counted and m = Volume of fibroblast culture media cells were resuspended in.

Alamar blue assay (metabolic activity)

[00403] Alamar blue is typically used to evaluate the metabolic activity of a population of cells using a fluorometric/colorimetric growth indicator. Specifically, the system incorporates an oxidation-reduction (REDOX) indicator that both fluoresces and changes colour in response to chemical reduction of growth medium resulting from cell growth, which can be related to the cytotoxicity of a test substance presented to the population when compared to cells which have not been treated. The assay was performed as described below.

[00404] HDF Cells were grown as described previously in this report and seeded at 2,000 cells per well in a volume of 2ml of Dulbecco's modified eagle medium and treated with various PDMS test samples in Indirect contact and direct contact via the use of crown insertions into 24 well plates. Control wells were also used with cells alone. These were then incubated for 48hrs (37°C, 5% C0₂). After incubation cell crowns and test samples were removed and 100μΙ of cell solution were transferred to a 96 well plate reader. 1 /10^th volume of Alamar blue reagent (life technologies) was added to each well and samples were protected from light and incubated for four hours (37°C, 5% C0₂), including alamar blue and media alone to use a negative control. Absorbance was then measured using a 96 well plate reader (570nm, 600nm as the reference). Cytotoxicity was calculated by the % reduction of alamar blue of control cells when compared with that of the treated cells, equation 5 was used; (εοχ)λ2 Αλ\ — {εοχ)λ\ Αλ2

— = Cytotoxicity

(εox)λ2 hλ^ — εox)λ^ Αλ2

Equation 5

A = Absorbance of test well

A = Absorbance of positive control

λι = 570nm

λ₂ = 600nm

[00405] FIG. 49 shows the comparision of % of cell survival of treated cells to untreated positive growth in direct contact, calculated using alamar blue assay.

[00406] FIG. 50 shows the comparision of % of cell survival of treated cells to untreated positive growth in indirect contact, calculated using alamar blue assay.

[00407] What can be seen from the direct contact studies (Fig. 48) is that the PDMS membrane without any PDMS-NVP-graft copolymer present is more toxic relative to when it contains either Low MW PDMS 1 a or Medium MW PDMS 2a.

[00408] As to be expected there is a reduction in cell viability obtained when exposing the cell populous to antimicrobial agents. Furthermore, this effect is dramatically increased when the substrate is in direct contact with the cells.

Picoqreen assay (cell proliferation)

[00409] The PicoGreen® dye is a fluorescent nucleic acid stain for quantitating double- stranded DNA (dsDNA), it can be used to measure the proliferation capacity of cells and thus be used to evaluate the cytotoxicity of various substrates on a population of cells compared with that of non treated cells.

[00410] HDF Cells were grown and seeded at 2,000 cells per well in a volume of 2ml of Dulbecco's modified eagle medium and treated with various PDMS test samples in Indirect contact and direct contact via the use of crown insertions into 24 well plates. Control wells were also used with cells alone. These were then incubated for 48hrs (37°C, 5% C0₂). After incubation cell crowns and test samples were removed and 100μΙ of cell solution were transferred to a 96 well plate reader. A standard curve was produced via materials provided in Picogreen assay kit, as well as a negative control. Quant-iT™ PicoGreen® reagent was then added to each test sample well, shaken and kept from sunlight. Sample fluorescence was measured using a 96 plate reader (excitation 480 nm, emission 520 nm). The amount of dsDNA can then be calculated using calibration curve provided.

[00411] FIG. 51 shows the comparison of the number of cells to untreated positive growth in direct contact, calculated using Picogreen assay.

[00412] FIG. 52 shows the comparison of the number of cells to untreated positive growth in indirect contact, calculated using Picogreen assay.

[00413] As with the alamar blue assay it can be seen that when the cells populous is treated with the substrate it is more cytotoxic in direct contact with them. Interestingly, the proliferative capacity of the cells is not increased when presented with the PDMS membrane with incorporated copolymer, while the metabolic activity of the cells is (alamar blue assay).

Claims

CLAIMS:

1 . A wound dressing for contact with skin and/or a wound, comprising a silicone- based composition coated onto a wound contact surface of the wound dressing, which silicone-based composition comprises:

- a silicone matrix material; and

- an amphiphilic co-polymer comprising a silicone polymer backbone Pi and one or more hydrophilic polymer chains P₂ attached to the silicone polymer backbone Pi, optionally via a linker; and

- optionally a hydrophilic agent.

2. The wound dressing as claimed in any preceding claim, wherein the amphiphilic co-polymer comprises:

a silicone polymer backbone Pi comprising a chain of polymerised monomer units Mi' derived or derivable from a monomer Mi, wherein by itself polymer Pi is substantially insoluble in water; and

one or more hydrophilic polymer chains P2, each comprising a chain of polymerised monomer units M₂' derived or derivable from a monomer M₂, attached to the silicone polymer backbone Pi , wherein by itself polymer P₂ is (substantially) soluble in water;

wherein each hydrophilic polymer chain P₂ is attached to the silicone polymer backbone Pi via a linker group L' at a grafting site of Formula la and/or Formula lb:

Formula la

wherein Mi' is a polymerised form of monomer Mi, and L' is a post-graft linker group derived from a pre-graft linker group L.

3. The wound dressing as claimed in claim 2, wherein Mi is selected from monomers of the formula M1 or a synthetic equivalent thereof: Ri

LG,— Si- -LG,

R₂

Formula M1

Formula M1 ' wherein:

Ri and R₂ are each independently selected from:

- hydroxy, amino, vinyl, or allyl,

n is an integer with a value of 2 or more.

4. The wound dressing as claimed in claim 3, wherein Ri and R₂ are each independently selected from (1 -8C)alkyl and aryl.

5. The wound dressing as claimed in claim 4, wherein Ri and R₂ are each independently selected from (1 -4C)alkyl and phenyl.

6. The wound dressing as claimed in claim 5, wherein both Ri and R₂ are methyl.

7. The wound dressing as claimed in claim 6, wherein the polymer Pi is polydimethylsiloxane (PDMS).

8. The wound dressing as claimed in any of claims 2 to 7, wherein the post-graft linker L' is attached to the polymer Pi via a functionalisable group of the polymerisable monomeric unit Mi' at the grafting site.

9. The wound dressing as claimed in claim 8, wherein the functionalisable group of the polymerisable monomeric unit Mi' at the grafting site is a nucleophilic functionalisable group selected from O , OH, NH₂, NHR (wherein R is selected from (1 -8C)alkyl, suitably from (1 -4C)alkyl).

10. The wound dressing as claimed in claim 8 or 9, wherein L' is a post-graft linker group derived from a pre-graft linker group L selected from (2-8C)alkenyl, (3-8C)alkenoyl, or (2-8C)alkenyloxycarbonyl.

1 1 . The wound dressing as claimed in any of claims 8 to 10, wherein L' is a post-graft linker group derived from a pre-graft linker group L that is (2-8C)alkenyloxycarbonyl.

12. The wound dressing as claimed in any of claims 8 to 1 1 , wherein L' is a post-graft linker group derived from a pre-graft linker group L that is vinyloxycarbonyl or allyloxycarbonyl.

13. The wound dressing as claimed in any of claims 2 to 12, wherein the polymer Pi only comprises grafting site(s) of Formula 1 a.

14. The wound dressing as claimed in claim 13, wherein the grafting site(s) are defined by the formula 1A:

Formula IA

15. The wound dressing as claimed in claim 14, wherein the grafting site(s) of formula 1A are selected from:

16. The wound dressing as claimed in any of claims 2 to 15, wherein at least 40% of available grafting sites upon the silicone polymer backbone Pi are functionalised with a linker group and a P₂ chain.

17. The wound dressing as claimed in any of claims 2 to 16, wherein M₂ is selected from alkenes substituted with one or more hydrophilic moieties which enable the corresponding polymer P₂ to be water soluble.

18. The wound dressing as claimed in any of claims 2 to 17, wherein M₂ is selected from N-vinylpyrrolidone (NVP to make PVP chains), N-vinylcapralactam, vinyl acetate, vinyl alcohol, hydrophilic acrylates and acrylic acids, hydrophilic arylamides, hydrophilic styrenes, and any salts or acid forms thereof, or any mixture thereof.

19. The wound dressing as claimed in any of claims 2 to 18, wherein M₂ is selected from N-vinylpyrrolidone (NVP to make PVP chains), N-vinylcapralactam, vinyl acetate, vinyl alcohol, acrylic acid, 2-aminoethyl methacrylate, methacrylic acid, 4-styrenesulfonic acid, Ν,Ν'-dimethyl acrylamide, glycerol monomethacrylate, potassium 3- sulfopropylmethacrylate, oligo(ethylene glycol) methacrylate, oligo(ethylene glycol) acrylate, 2-(dimethylamino)ethyl methacrylate, 2-(diisopropylamino)ethyl methacrylate, 2- (methacryloyloxy)ethyl phosphorylcholine, 2-Hydroxyethyl acrylate, 2-Hydroxyethyl methacrylate, methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate or methyl iodiide-quaternized 2-(dimethylamino)ethyl methacrylate, 2-(methacryloyloxy)ethyl succinate, and any salts or acid forms thereof, or any mixture thereof

20. The wound dressing as claimed in claim 19, wherein M₂ is N-vinylpyrrolidone and P₂ is poly(N-vinylpyrrolidone) (PVP), optionally a homopolymer thereof.

21 . The wound dressing as claimed in claim 20, wherein the amphiphilic co-polymer is a PDMS-PVP co-polymer.

22. The wound dressing as claimed in any preceding claim, wherein the polymer Pi has a molecular weight (M_w) between 1000 and 20000 g/mol, and the polymer chain(s) P₂ have a molecular weight (M_w) between 20,000 and 200,000 g/mol.

23. The wound dressing as claimed in any preceding claim, wherein the Pi : P₂ molar ratio of monomer units within the amphiphilic co-polymer is between 2:1 and 1 :9.

24. The wound dressing as claimed in any preceding claim, wherein the molar ratio of monomer units used in the formation of the amphiphilic co-polymer (i.e. the moles of M₂ used relative to the number of moles of Mi' units in the Pi polymer) is between 4:1 and 1 :4.

25. The wound dressing as claimed in any preceding claim, wherein the amphiphilic co-polymer is in the form of particles with a hydrophilic core and a hydrophobic shell.

26. The wound dressing as claimed in any preceding claim, wherein the silicone matrix material is a silicone or polysiloxane that is substantially insoluble in water.

27. The wound dressing as claimed in any preceding claim, wherein the silicone matrix material is polydimethylsiloxane (PDMS).

28. The wound dressing as claimed in any preceding claim, wherein the silicone-based composition comprises a hydrophilic agent that is encapsulated within particles of the amphiphilic co-polymer.

29. The wound dressing as claimed in any preceding claim, wherein the hydrophilic agent is a therapeutic agent.

30. The wound dressing as claimed in claim 29, wherein the therapeutic agent is for use in treating wound infections.

31 . The wound dressing as claimed in claim 28 or 29, wherein the hydrophilic agent is an antimicrobial agent.

32. The wound dressing as claimed in claim 31 , wherein the antimicrobial agent is selected from the group including silver, iodine and derivates (e.g. Povidone iodine (PVP- I), Cadexomer iodine (CI)), chlorhexidine, Polyhexamethylene biguanide (PHMB), Ethylene diamine tetra acetic acid (EDTA), Chlorhexidine (CHX), Quaternary ammonium compounds (QACs) and derivatives, Octenidine hydrochloride (OH), Benzalkonium chloride (BAC).

33. The wound dressing as claimed in any preceding claim, wherein the silicone-based composition comprises:

- 20,000-90,000 parts by weight silicone matrix material;

100-1 ,000 parts by weight amphiphilic co-polymer; and

10-500 parts by weight hydrophilic agent;

wherein optionally any remaining weight balance consists essentially of a hydrophilic and/or a hydrophobic solvent.

34. The wound dressing as claimed in any preceding claim, wherein the weight ratio of amphiphilic co-polymer to hydrophilic agent is between 20:1 and 1 :1 .

35. The wound dressing as claimed in any preceding claim, wherein the weight ratio of amphiphilic co-polymer to silicone matrix material is between 1 :1 ,000 and 1 :5.

36. A silicone-based composition, comprising:

- a silicone matrix material; and - an amphiphilic co-polymer comprising a silicone polymer backbone Pi and one or more hydrophilic polymer chains P₂ attached to the silicone polymer backbone Pi, optionally via a linker; and

- optionally a hydrophilic agent;

optionally as further defined in any of claims 2 to 35.

37. An amphiphilic co-polymer comprising:

a silicone polymer backbone Pi comprising a chain of polymerised monomer units Mi' derived or derivable from a monomer Mi, wherein by itself polymer Pi is (substantially) insoluble in water; and

- one or more hydrophilic polymer chains P2, each comprising a chain of polymerised monomer units M₂' derived or derivable from a monomer M₂, attached to the silicone polymer backbone Pi , wherein by itself polymer P₂ is (substantially) soluble in water;

Formula la

wherein Mi' is a polymerised form of monomer Mi, and L' is a post-graft linker group (i.e. derived from a pre-graft linker group L);

wherein Mi is selected from monomers of the formula M1 or a synthetic equivalent thereof:

Ri

LG-i— Si LG₂

R₂

Formula M1

Formula M1 ' wherein:

Ri and R₂ are each independently selected from:

- hydroxy, amino, vinyl, or allyl,

n is an integer with a value of 2 or more;

optionally as further defined in any of claims 3 to 25.

38. A process for the preparation of an amphiphilic co-polymer, the process comprising:

Ri

LG-i— Si LG₂

R₂

Formula M1

Formula M1 '

wherein:

Ri and R₂ are each independently selected from:

- hydroxy, amino, vinyl, or allyl;

n is an integer with a value of 2 or more.

b) preparing a functionalised silicone polymer (Pi-L) by functionalising one or more polymerised monomer units Mi' of the silicon polymer backbone Pi to install thereupon one or more pre-graft linker groups L to provide within the polymer Pi one or more grafting sites of Formula 2a or Formula 2b;

Formula 2a Formula 2b

c) polymerising a monomer M₂ in the presence of the functionalised silicone polymer (Pi-L) to grow (or attach), from the one or more pre-graft linker group(s) L thereof, one or more hydrophilic polymer chains P₂ (suitably at the terminal monomer unit Mi' thereof) to produce an amphiphilic co-polymer having one or more grafting sites of Formula la and/or Formula lb:

Formula la Formula lb wherein L' is a post-graft linker group derived from the pre-graft linker group L;

wherein by itself polymer P₂ is (substantially) soluble in water;

optionally as further defined in any of claims 3 to 25.

39. An amphiphilic co-polymer obtained by the process of claim 38.

40. A kit of parts comprising a wound dressing or a wound dressing as defined in any of claims 1 to 35, and a hydrophilic agent.

41 . A use of an amphiphilic co-polymer as claimed in claim 37 or 39 or as defined in any of claims 1 to 35, or a silicone-based composition as claimed in claim 35, for delivering a hydrophilic agent to a wound that is infected, suspected to be infected, or at risk of being infected.

42. A process for the preparation of a particulate composition, the process comprising contacting an amphiphilic copolymer as claimed in claim 37 or 39 or as defined in any of claims 1 to 35 with a hydrophobic solvent.

43. A particulate composition obtained by the process of claim 42.

44. A process for the preparation of an agent-loaded particulate composition, the process comprising contacting a particulate composition as claimed in claim 43 with a hydrophilic agent, optionally in the presence of a hydrophilic solvent.

45. An agent-loaded particulate composition obtained by the process of claim 44.

46. A wound dressing, silicone-based composition, an amphiphilic co-polymer, a process, a kit of parts, a use, a particulate composition, agent-loaded particulate composition, as substantially hereinbefore described with reference to the accompanying examples and figures.