WO2023104872A1

WO2023104872A1 - Surface coating comprising microfibrillated cellulose

Info

Publication number: WO2023104872A1
Application number: PCT/EP2022/084763
Authority: WO
Inventors: Zhenyu Zhang; Peter Fryer; Shaojun QI; Ioannis KIRATZIS; Stuart Clarke; David Skuse
Original assignee: Fiberlean Technologies Limited; The University Of Birmingham; Cambridge Enterprise Ltd
Priority date: 2021-12-09
Filing date: 2022-12-07
Publication date: 2023-06-15
Also published as: GB202117810D0

Abstract

Articles comprising a surface and having on said surface a coating comprising microfibrillated cellulose, methods of applying a coating comprising microfibrillated cellulose to a surface, compositions comprising microfibrillated cellulose, and the use of such compositions in methods of preparing an antimicrobial surface coating.

Description

Surface coating comprising microfibrillated cellulose

FIELD OF INVENTION [0001] Articles comprising a surface and having on said surface a coating comprising microfibrillated cellulose, methods of applying a coating comprising microfibrillated cellulose to a surface, compositions comprising microfibrillated cellulose, and the use of such compositions in methods of preparing an antimicrobial surface coating. BACKGROUND OF THE INVENTION

[0002] Severe acute respiratory syndrome coronavirus 2 (SARS-C0V-2), responsible for the global pandemic of coronavirus disease 2019 (COVID-19), belongs to the family of ‘enveloped viruses’ along with influenza viruses and the also lethal 2002 severe acute respiratory syndrome coronavirus 1 (SARS-C0V-1) and the 2011 Middle East respiratory syndrome coronavirus (MERS-CoV). In vitro SARS-C0V-2 virions are often wrapped within respiratory droplets and aerosols generated by a diseased person via coughs, sneezes, talking or simply breathing, making them highly contagious, particularly in enclosed spaces. Transmission of SARS-C0V-2 can thus occur through direct exposure to respiratory droplets (>5-10 pm) or aerosols (<5 pm) that include virus. Surface transmission is considered a likely mode by the scientific community and public health authorities. It takes place by contact with fomite surfaces that were contaminated by infectious respiratory secretions or droplets. SARS-C0V-2 RNA has been widely detected on high-touch surfaces such as handles (e.g. door handles or trash can handles), handrails, shared sanitation facilities in hospitals, schools and community settings, recently cold chain surfaces, etc. Viable SARS-C0V-2 were found on those surfaces for periods ranging from hours to days. Therefore, one of the primary intervention measures adopted by countries and territories around the world amid the COVID-19 pandemic is frequent cleaning and disinfection of communal surfaces. [0003] Possible routes for reducing surface transmission of viruses such as SAR-CoV- 2 include (a) chemical disinfection, (b) non-contact disinfection and (c) antiviral coatings. Chemical detergents, such as chlorine bleach, phenolics and quaternary ammonium compounds have been reported as rapid solutions for disinfection of virus contaminated surfaces. Such detergent-based agents inactivate viruses by disrupting the lipid envelop of the virion. However, they normally do not provide long lasting protection to the surface, and the concerns over their environmental impact and cytotoxicity limit their regular use in settings such as households and offices. The current practice of large-scale, frequent, indiscriminate and sometimes more-than- needed application of disinfectants amid COVID-19 is worrying, posing threats to the urban environment, biodiversity and the public health.

[0004] Non-contact disinfection can be delivered from a distance via various energy sources. SARS-C0V-2 has been found to be stable at 4 °C but very sensitive to heat. It has been shown to be possible to disinfect personal protective equipment (PPE), including N95 masks by gently heating at 70 °C and 0% relative humidity for 1 hour.

Heat inactivation was also achieved by incubating SARS-C0V-2 stock at 8o°C for 1 hour. Thermal inactivation is, however, not flexible as it requires heating equipment which requires investment and there are limitations on the dimensions of the objects that can be treated. [0005] Antiviral surfaces offer a passive approach against harmful pathogens, including coronaviruses. Naturally occurring antiviral surfaces, for example, are found on specific herbs containing antiviral inhibitors such as myricetin, scutellarein and phenolic compounds which destroy viruses upon contact. Engineered surface coatings incorporating selected metal elements, notably copper and silver, have shown satisfactory virucidal properties by disrupting the disulphide bonds of virus proteins and/or releasing reactive oxygen species (ROS) that damage the nucleic acids of the virus. Another group of antiviral materials, and the probably most popular ones, include quaternary ammonium compounds (QACs). The positively charged groups and lipophilic tails on QACs can readily bond to and disrupt negatively charged virus envelopes, conferring a good inactivation efficiency provided the QAC structure matches the lipid composition and envelope protein density of the targeted virus. [0006] The conventional strategies for antiviral surfaces have been primarily focused on modifying surfaces with chemical compounds which target directly the virus membrane. However, each of these approaches has their associated drawbacks, not least that they target a virus membrane which is often not what is in direct contact with the surface in question (for example, in the case of virions that are wrapped within respiratory droplets and aerosols).

[0007] Notwithstanding the foregoing technologies, there remains a need for easily manufactured and readily available antimicrobial products that reduce or prevent the transmission of infectious disease such as SARS-CoV-2. SUMMARY OF THE INVENTION

[0008] A first aspect of the invention provides an article comprising a surface and having on said surface a coating comprising at least about 8o wt% microfibrillated cellulose based on the total weight of the coating.

[0009] A second aspect of the invention provides an article comprising a non-porous surface and having on said surface a coating comprising microfibrillated cellulose.

[0010] A third aspect of the invention provides a method of applying a coating to a surface, the method comprising:

(i) treating the surface with a composition comprising a suspension of microfibrillated cellulose in a liquid component comprising water and optionally a water miscible component; and

(ii) obtaining a surface coated with a coating comprising microfibrillated cellulose. [0011] A fourth aspect of the invention provides a composition comprising a suspension of microfibrillated cellulose in a liquid component comprising water and optionally a water miscible component.

[0012] A fifth aspect of the invention provides a method of applying a coating to a surface, the method comprising (i) treating the surface with a composition according to the fourth aspect of the invention; and (ii) obtaining a surface coated with a coating comprising microfibrillated cellulose.

[0013] A sixth aspect of the invention provides an article comprising a surface coated with a coating applied according to the methods of the third or fifth aspects of the invention.

[0014] A seventh aspect of the invention provides an article comprising a surface coated with the composition of the fourth aspect of the invention.

[0015] An eighth aspect of the invention provides the use of a composition according to the fourth aspect of the invention in a method of preparing an antimicrobial surface coating.

[0016] A ninth aspect of the invention provides the use of microfibrillated cellulose for inactivating a microbe capable of causing an infection in a subject.

[0017] A tenth aspect of the invention provides a method of inactivating a microbe capable of causing an infection in a subject, comprising using microfibrillated cellulose.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1A is an optical microscopic image of an MFC thin film prepared by the herein described spin coating method.

[0019] Figure 1B is an optical microscopic image of an MFC thin film prepared by the herein described spray coating method. [0020] Figure 1C is an atomic force microscopic image of an MFC thin film prepared by the herein described spin coating method.

[0021] Figure 1D is an atomic force microscopic image of an MFC thin film prepared by the herein described spray coating method. [0022] Figure 1E is a scanning electron microscopic image of an MFC thin film prepared by the herein described spin coating method.

[0023] Figure 1F is a scanning electron microscopic image of an MFC thin film prepared by the herein described spray coating method.

[0024] Figure 2A shows the height distribution of MFC thin films prepared by the herein described spin coating method and spray coating method.

[0025] Figure 2B shows uncoated glass (top), a spray coated MFC film (middle) and a spin coated MFC film (bottom) in natural light:

[0026] Figure 3A shows the roughness and waviness of a series of spin coated MFC thin films prepared according to the herein described spin coating methods.

[0027] Figure 3B shows the porosity and mean pore size of a series of spin coated MFC thin films prepared according to the herein described spin coating methods.

[0028] Figures 4A to 4F show optical microscopic images of the MFC thin films before and after the scraping tests of example 1.

[0029] Figure 5A shows the contact angle of the water droplets of example 2.1.

[0030] Figure 5B shows the disappearance time of the water droplets of example 2.1.

[0031] Figures 6 to 9 show the evaporation behavior of the droplets of examples 2.2.1 to 2.2.4, respectively.

[0032] Figure 10 shows the redistribution of 1 mm diameter artificial saliva droplets according to examples 3.1, 3.2 and 3.3.

[0033] Figure 11 shows the redistribution of 1 mm diameter artificial saliva droplets according to examples 3.4, 3.5 and 3.6. [0034] Figure 12 shows the redistribution of 1 mm diameter artificial saliva droplets according to examples 3.7, 3.8 and 3.9.

[0035] Figure 13 shows the area of fluorescent stained mucin on the artificial skin following the touch tests in examples 3.1 to 3.6. [0036] Figure 14 shows the area of fluorescent stained mucin on the artificial skin following the touch tests in examples 3.7 to 3.12.

[0037] Figure 15 shows the effect of the settlement time and surface specification on resultant infection with SARS-C0V-2 as described in example 4.1.

[0038] Figure 16 shows the viability of E.coli after incubation on the MFC thin film and glass for 1 h and 24 h as described in example 4.2.

[0039] Figure 17 shows the viability of S.epidermidis after incubation on the MFC thin film and glass for 1 h and 24 h as described in example 4.2.

[0040] Figure 18 is an atomic force microscopy image of the MFC coating exposed to viral titre showing that the porous coating was able to capture individual virus as described in example 4.3.

DETAILED DESCRIPTION OF THE INVENTION

[0041] Antimicrobial effect

[0042] As used herein the term ‘antimicrobial surface coating’ is intended to mean that the external surface of a substrate on which coating according to the invention is applied is active against microbes so as to prevent or reduce the transmission of the microbes from the surface of said substrate. The term antimicrobial refers to the effect on bacteria, viruses and/or fungi. In some embodiments, the ‘antimicrobial surface coating’ is an ‘antiviral surface coating’. In some embodiments, the microbe is selected from the group consisting of bacteria, viruses and/ or fungi. In some embodiments, the microbe is a virus. [0043] In some embodiments, the coating has an inactivating effect on a microbe capable of causing an infection in a subject. In some embodiments, the microbe is bacteria, optionally E. coli and/or S. epidermidis. In some embodiments, the subject is a human. [0044] In some embodiments, the coating has an inactivating effect on a virus capable of causing a viral infection in a subject optionally a virus capable of causing an airborne viral infection in a subject. In some embodiments, the virus is an RNA virus. In some embodiments, the virus is an RNA virus selected from the group consisting of a coronavirus (including a coronavirus selected from MERS-CoV, SARS-CoV, and SARS- C0V-2), an influenza virus, a rhinovirus, Measles virus and Mumps virus. In some embodiments, the virus is a coronavirus. In some embodiments, the virus is SARS-CoV- 2. In some embodiments, the subject is a human.

[0045] As used herein an ‘airborne viral infection’ is an infection transmitted by an airborne virus. An ‘airborne virus’ is a virus in which the disease spreads in particles in exhaled air. These particles include respiratory droplets (>5-10 pm) and aerosols (< 5 pm) that include the virus. Transmission of an airborne viral infection can also take place through a subject touching fomite surfaces that have been contaminated by respiratory secretions or droplets expelled by an infected subject.

[0046] As used herein the term ‘inactivating effect on a microbe’ means that the coating improves microbe inactivation compared to a corresponding untreated surface. Such an improvement in microbe inactivation may include an improvement in the prevention or reduction of transmission of the microbe from the surface. Such an improvement may include an increase in the speed and/or extent of microbe inactivation. As used herein the corresponding untreated surface, refers to the same surface or an equivalent surface prior to the application of the coating. For example if the coated surface is glass, the corresponding untreated surface is the same type of glass without the coating such that a like-for-like comparison can be made. [0047] As used herein the term ‘inactivating effect on a virus’ means that the coating improves viral inactivation compared to a corresponding untreated surface. Such an improvement in viral inactivation may include an improvement in the prevention or reduction of transmission of the virus from the surface. Such an improvement may include an increase in the speed and/or extent of viral inactivation. As used herein the corresponding untreated surface, refers to the same surface or an equivalent surface prior to the application of the coating. For example if the coated surface is glass, the corresponding untreated surface is the same type of glass without the coating such that a like-for-like comparison can be made. In some embodiments, the antiviral activity is determined according to ISO 21702:2019 (Measurement of antiviral activity on plastics and other non-porous surfaces).

[0048] Coating composition

[0049] In some embodiments, the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 40 wt% based on the total weight of the composition. In some embodiments, the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 30 wt% based on the total weight of the composition. In some embodiments, the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 25 wt% based on the total weight of the composition. In some embodiments, the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 20 wt% based on the total weight of the composition. In some embodiments, the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 15 wt% based on the total weight of the composition. In some embodiments, the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 10 wt% based on the total weight of the composition. In some embodiments, the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 5 wt% based on the total weight of the composition. In some embodiments, the composition comprises microfibrillated cellulose in an amount of about o.i to about 4 wt% based on the total weight of the composition. In some embodiments, the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 3 wt% based on the total weight of the composition. In some embodiment, the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 2 wt% based on the total weight of the composition.

[0050] As used herein reference to the ‘total weight of the composition’ includes all components of the composition including the weight of all liquids present in the composition unless otherwise stated.

[0051] In some embodiments, the composition comprises a suspension of microfibrillated cellulose in a liquid component. In some embodiments, the liquid component comprises one or more liquids, for example two, three, four or five liquids. Preferably, the liquid component comprises two liquids or three liquids. In some embodiments, the liquid component comprises liquids selected from the group consisting of water, methanol, ethanol, 1-propanol, 2-propanol, dimethylsulfoxide, acetonitrile, acetone, tetrahydrofuran and mixtures thereof.

[0052] In some embodiments, the liquid component comprises water. In some embodiments, the liquid component comprises water and optionally one or more other liquids. In some embodiments, the liquid component comprises water and optionally one or more other liquids. In some embodiments, the liquid component comprises a liquid selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, dimethylsulfoxide, acetonitrile, acetone, tetrahydrofuran and mixtures thereof. In some embodiments, the composition comprises a suspension of microfibrillated cellulose in a liquid comprising water and one or more other liquids optionally selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, dimethylsulfoxide, acetonitrile, acetone, tetrahydrofuran and mixtures thereof.

[0053] In some embodiments, the composition comprises a suspension of microfibrillated cellulose in a liquid component comprising water and one or more polar liquids. In some embodiments, the composition comprises a suspension of microfibrillated cellulose in a liquid comprising water and one or more alcohols optionally selected from the group consisting of methanol, ethanol, 1-propanol, 2- propanol and mixtures thereof. In some embodiments, the composition comprises a suspension of microfibrillated cellulose in a liquid component comprising water and ethanol.

[0054] In some embodiments, the composition comprises a suspension of microfibrillated cellulose in a liquid component comprising water and optionally one or more other liquids, wherein the ratio of water : other liquids is from about 1 : 1 to about 1 : io (v : v), optionally from about 1 : 3 to about 1 : 7 (v : v). In some embodiments, the composition comprises a suspension of microfibrillated cellulose in a liquid component comprising water and one or more alcohols (optionally selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol and mixtures thereof), wherein the ratio of water : alcohols is from about 1 : 1 to about 1 : 10 (v : v), optionally from about 1 : 3 to about 1 : 7 (v : v). In some embodiments, the alcohol is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol and mixtures thereof.

[0055] In some embodiments, the microfibrillated cellulose content of the composition is in the range of from about 0.01 to about 99.9 wt% based on the weight of solids in the composition. In some embodiment, the microfibrillated cellulose content of the composition is in the range of about 70 to about 99 wt%, in the range of about 80 to about 99 wt%, or in the range of from about 90 to about 99 wt% of the solids in the composition.

[0056] In some embodiments, the composition is sprayable.

[0057] Microfibrillated Cellulose

[0058] The microfibrillated cellulose used in the coating according to the present invention can be prepared using methods known in the art. [0059] Microfibrillated cellulose (MFC) shall in the context of the patent application mean a nanoscale cellulose particle fiber or fibril with at least one dimension less than about IOO nm. MFC comprises partly or totally fibrillated cellulose or lignocellulose fibers. The liberated fibrils have a diameter less than about ioo nm, whereas the actual fibril diameter or particle size distribution and/ or aspect ratio (length/ width) depends on the source and the manufacturing methods.

[0060] The smallest fibril is called elementary fibril and has a diameter of approximately 2-4 nm (see e.g. Chinga-Carrasco, G., Cellulose fibres, nanofibrils and microfibrils: The morphological sequence of MFC components from a plant physiology and fibre technology point of view, Nanoscale Research Letters 2011, 6:417), while it is common that the aggregated form of the elementary fibrils, also defined as microfibril (Fengel, D., Ultrastructural behavior of cell wall polysaccharides, Tappi J., March 1970, Vol 53, No. 3.), is the main product that is obtained when making MFC e.g. by using an extended refining process or pressure- drop disintegration process. Depending on the source and the manufacturing process, the length of the fibrils can vary from around 1 to more than 10 micrometers. A coarse MFC grade might contain a substantial fraction of fibrillated fibers, i.e. protruding fibrils from the tracheid (cellulose fiber), and with a certain amount of fibrils liberated from the tracheid (cellulose fiber). [0061] There are different acronyms for MFC such as cellulose microfibrils, fibrillated cellulose, nanofibrillated cellulose, fibril aggregates, nanoscale cellulose fibrils, cellulose nanofibers, cellulose nanofibrils, cellulose microfibers, cellulose fibrils, microfibrillar cellulose, microfibril aggregates and cellulose microfibril aggregates.

MFC can also be characterized by various physico-chemical properties such as large surface area or its ability to form a gel-like material at low solid contents (1-5 wt %) when dispersed in water. The cellulose fiber is preferably fibrillated to such an extent that the final specific surface area of the formed MFC is from about 1 to about 300 m²/g, such as from about i to about 200 m²/g or more preferably about 50-200 m²/g when determined for a freeze-dried material with the BET method.

[0062] The nanofibrillar cellulose may contain some hemicelluloses, of which; the amount is dependent on the plant source. Mechanical disintegration of the pre-treated fibers, e.g. hydrolysed, pre-swelled, or oxidized cellulose raw material is carried out with suitable equipment such as a refiner, grinder, homogenizer, colloider, friction grinder, ultrasound sonicator, fluidizer such as microfluidizer, macrofluidizer or fluidizer-type homogenizer. Depending on the MFC manufacturing method, the product might also contain fines, or nanocrystalline cellulose or other chemicals present in wood fibers or in papermaking process. The product might also contain various amounts of micron size fiber particles that have not been efficiently fibrillated.

MFC is produced from wood cellulose fibers, both from hardwood or softwood fibers. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. It is preferably made from pulp including pulp from virgin fiber, e.g. mechanical, chemical and/or thermo mechanical pulps. It can also be made from broke or recycled paper.

[0063] In some embodiments, the microfibrillated cellulose has a Schopper Riegler value (SR.degree.) of more than about 85 SR.degree., or more than about 90

SR.degree., or more than about 92 SR.degree. The Schopper-Riegler value can be determined through the standard method defined in EN ISO 5267-1.

[0064] The microfibrillated cellulose preferably has a water retention value of at least about 200%, more preferably at least about 250%, most preferably at least about 300%. The addition of certain chemicals may influence the water retention value.

[0065] The above described definition of MFC includes, but is not limited to, the new proposed TAPPI standard W13021 on cellulose nanofibril (CNF) defining a cellulose nanofiber material containing multiple elementary fibrils with both crystalline and amorphous region. [0066] In some embodiments, the microfibrillated cellulose is obtained from a chemical pulp, or a chemithermomechanical pulp, or a mechanical pulp, or thermomechanical pulp, including, for example, Northern Bleached Softwood Kraft pulp (“NBSK”), Bleached Chemi-Thermo Mechanical Pulp (“BCTMP”), or a recycled pulp, or a paper broke pulp, or a papermill waste stream, or waste from a papermill, or combinations thereof.

[0067] In some embodiments, the pulp source is kraft pulp, or bleached long fibre kraft pulp.

[0068] In some embodiments, the pulp source is softwood pulp selected from spruce, pine, fir, larch and hemlock or mixed softwood pulp.

[0069] In some embodiments, the pulp source is hardwood pulp selected from eucalyptus, aspen and birch, or mixed hardwood pulps.

[0070] In some embodiments, the pulp source is eucalyptus pulp, spruce pulp, pine pulp, beech pulp, hemp pulp, acacia cotton pulp, and mixtures thereof. [0071] In some embodiments, a fibrous substrate comprising cellulose has a

Canadian Standard Freeness equal to or less than about 450 cm3-

[0072] In some embodiments, the invention relates to modifications, for example, improvements, to the methods and compositions described in WO-A-2010/ 131016, the entire contents of which are hereby incorporated by reference. [0073] WO-A-2010/131016 discloses a process for preparing microfibrillated cellulose comprising microfibrillating, e.g., by grinding, a fibrous material comprising cellulose, optionally in the presence of grinding medium and inorganic particulate material.

When used as a filler in paper, for example, as a replacement or partial replacement for a conventional mineral filler, the microfibrillated cellulose obtained by said process, optionally in combination with inorganic particulate material improved the burst strength properties of the paper. That is, relative to a paper filled with exclusively mineral filler, paper filled with the microfibrillated cellulose was found to have improved burst strength. In other words, the microfibrillated cellulose filler was found to have paper burst strength enhancing attributes. In one particularly advantageous embodiment of that invention, the fibrous material comprising cellulose was ground in the presence of a grinding medium, optionally in combination with inorganic particulate material, to obtain microfibrillated cellulose having a fibre steepness of from about 20 to about 50.

[0074] The method described in WO-A-2010/131016 comprises a step of microfibrill ating a fibrous substrate comprising cellulose by grinding in the presence of a particulate grinding medium which is to be removed after the completion of grinding. By “microfibrillating” is meant a process in which microfibrils of cellulose are liberated or partially liberated as individual species or as small aggregates as compared to the fibres of the pre-microfibrillated pulp. Typical cellulose fibres (i.e., pre-microfibrillated pulp) suitable for use in papermaking include large aggregates of hundreds or thousands of individual cellulose fibrils. By microfibrillating the cellulose, particular characteristics and properties, including the characteristics and properties described herein, are imparted to the microfibrillated cellulose and the compositions comprising the microfibrillated cellulose.

[0075] The fibrous substrate comprising cellulose (variously referred to herein as “fibrous substrate comprising cellulose,” “cellulose fibres,” “fibrous cellulose feedstock,” “cellulose feedstock” and “cellulose-containing fibres (or fibrous,” etc.) may be derived from recycled pulp or a papermill broke and/or industrial waste, or a paper stream rich in mineral fillers and cellulosic materials from a papermill.

[0076] The recycled cellulose pulp may be beaten (for example in a Valley beater) and/or otherwise refined (for example, processing in a conical or plate refiner) to any predetermined freeness, reported in the art as Canadian standard freeness (CSF) in cm3. CSF means a value for the freeness or drainage rate of pulp measured by the rate that a suspension of pulp maybe drained, and this test is carried out according to the T 227 cm-09 TAPPI standard. For example, the cellulose pulp may have a Canadian standard freeness of about 10 cm3 _or greater prior to being microfibrillated. The recycled cellulose pulp may have a CSF of about 700 cm3 _Or less, for example, equal to or less than about 650 cm3, _Or equal to or less than about 600 cm3, _Or equal to or less than about 550 cm3, _Or equal to or less than about 500 cm3, _Or equal to or less than about 450 cm3, _Or equal to or less than about 400 cm3, _Or equal to or less than about 350 cm3, or equal to or less than about 300 cm3, _Or equal to or less than about 250 cm3, or equal to or less than about 200 cm?', or equal to or less than about 150 cm?', or equal to or less than about 100 cm3, _Or equal to or less than about 50 cm3. The recycled cellulose pulp may have a CSF of about 20 to about 700. The recycled cellulose pulp may then be dewatered by methods well known in the art, for example, the pulp maybe filtered through a screen in order to obtain a wet sheet comprising at least about 10% solids, for example at least about 15% solids, or at least about 20% solids, or at least about 30% solids, or at least about 40% solids. The recycled pulp maybe utilized in an unrefined state, that is to say without being beaten or dewatered, or otherwise refined. [0077] In some embodiments, the microfibrillated cellulose may also be prepared from recycled pulp or a papermill broke and/or industrial waste, or a paper stream rich in mineral fillers and cellulosic materials from a papermill.

[0078] The fibrous substrate comprising cellulose maybe added to a grinding vessel fibrous substrate comprising cellulose in a dry state. For example, a dry paper broke maybe added directly to the grinder vessel. The aqueous environment in the grinder vessel will then facilitate the formation of a pulp.

[0079] The inorganic particulate material, when present, may, for example, be an alkaline earth metal carbonate or sulphate, such as calcium carbonate, magnesium carbonate, dolomite, gypsum, a hydrous kandite day such as kaolin, halloysite or ball clay, an anhydrous (calcined) kandite clay such as metakaolin or fully calcined kaolin, talc, mica, perlite or diatomaceous earth, or magnesium hydroxide, or aluminum trihydrate, or combinations thereof.

[0080] A preferred inorganic particulate material for use is calcium carbonate.

Hereafter, the invention may tend to be discussed in terms of calcium carbonate, and in relation to aspects where the calcium carbonate is processed and/ or treated. The invention should not be construed as being limited to such embodiments.

[0081] The particulate calcium carbonate optionally used in the present invention may be obtained from a natural source by grinding. Ground calcium carbonate (GCC) is typically obtained by crushing and then grinding a mineral source such as chalk, marble or limestone, which may be followed by a particle size classification step, in order to obtain a product having the desired degree of fineness. Other techniques such as bleaching, flotation and magnetic separation may also be used to obtain a product having the desired degree of fineness and/or color. The particulate solid material may be ground autogenously, i.e. by attrition between the particles of the solid material themselves, or, alternatively, in the presence of a particulate grinding medium comprising particles of a different material from the calcium carbonate to be ground. These processes may be carried out with or without the presence of a dispersant and biocides, which maybe added at any stage of the process.

[0082] Precipitated calcium carbonate (PCC) maybe used as the source of particulate calcium carbonate in the present invention, and may be produced by any of the known methods available in the art. TAPPI Monograph Series No 30, "Paper Coating Pigments", pages 34-35 describes the three main commercial processes for preparing precipitated calcium carbonate which is suitable for use in preparing products for use in the paper industry, but may also be used in the practice of the present invention. In all three processes, a calcium carbonate feed material, such as limestone, is first calcined to produce quicklime, and the quicklime is then slaked in water to yield calcium hydroxide or milk of lime. In the first process, the milk of lime is directly carbonated with carbon dioxide gas. This process has the advantage that no by-product is formed, and it is relatively easy to control the properties and purity of the calcium carbonate product. In the second process the milk of lime is contacted with soda ash to produce, by double decomposition, a precipitate of calcium carbonate and a solution of sodium hydroxide. The sodium hydroxide may be substantially completely separated from the calcium carbonate if this process is used commercially. In the third main commercial process, the milk of lime is first contacted with ammonium chloride to give a calcium chloride solution and ammonia gas. The calcium chloride solution is then contacted with soda ash to produce by double decomposition precipitated calcium carbonate and a solution of sodium chloride. The crystals can be produced in a variety of different shapes and sizes, depending on the specific reaction process that is used.

The three main forms of PCC crystals are aragonite, rhombohedral and scalenohedral, all of which are suitable for use in the present invention, including mixtures thereof.

[0083] Wet grinding of calcium carbonate involves the formation of an aqueous suspension of the calcium carbonate which may then be ground, optionally in the presence of a suitable dispersing agent. Reference maybe made to, for example, EP-A- 614948 (the contents of which are incorporated by reference in their entirety) for more information regarding the wet grinding of calcium carbonate.

[0084] In some circumstances, minor additions of other minerals maybe included, for example, one or more of kaolin, calcined kaolin, wollastonite, bauxite, talc or mica, could also be present.

[0085] When the inorganic particulate material is obtained from naturally occurring sources, it maybe that some mineral impurities will contaminate the ground material. For example, naturally occurring calcium carbonate can be present in association with other minerals. Thus, in some embodiments, the inorganic particulate material includes some extent of impurities. In general, however, the inorganic particulate material used in the invention will contain less than about 5% by weight, preferably less than about 1% by weight, of other mineral impurities.

[0086] The inorganic particulate material which maybe used during a microfibrillating step will preferably have a particle size distribution in which at least about 10% by weight of the particles have an equivalent spherical diameter (e.s.d.) of less than 2 pm, for example, at least about 20% by weight, or at least about 30% by weight, or at least about 40% by weight, or at least about 50% by weight, or at least about 60% by weight, or at least about 70% by weight, or at least about 80% by weight, or at least about 90% by weight, or at least about 95% by weight, or about 100% of the particles have an e.s.d of less than 2 pm.

[0087] Unless otherwise stated, particle size properties referred to herein for the inorganic particulate materials are as measured in a well-known manner by sedimentation of the particulate material in a fully dispersed condition in an aqueous medium using a Sedigraph 5100 machine as supplied by Micromeritics Instruments Corporation, Norcross, Ga., USA (telephone: +1770 6623620; web-site: www.micromeritics.com), referred to herein as a "Micromeritics Sedigraph 5100 unit". Such a machine provides measurements and a plot of the cumulative percentage by weight of particles having a size, referred to in the art as the ' equivalent spherical diameter' (e.s.d), less than given e.s.d values. The mean particle size d₅₀ is the value determined in this way of the particle e.s.d at which there are 50% by weight of the particles which have an equivalent spherical diameter less than that d₅₀ value.

[0088] Alternatively, where stated, the particle size properties referred to herein for the inorganic particulate materials are as measured by the well-known conventional method employed in the art of laser light scattering, using a Malvern Mastersizer S machine as supplied by Malvern Instruments Ltd (or by other methods which give essentially the same result). In the laser light scattering technique, the size of particles in powders, suspensions and emulsions maybe measured using the diffraction of a laser beam, based on an application of Mie theory. Such a machine provides measurements and a plot of the cumulative percentage by volume of particles having a size, referred to in the art as the 'equivalent spherical diameter' (e.s.d), less than given e.s.d values. The mean particle size d₅₀ is the value determined in this way of the particle e.s.d at which there are 50% by volume of the particles which have an equivalent spherical diameter less than that d₅₀ value.

[0089] Unless otherwise stated, particle size properties of the microfibrillated cellulose materials are measured by the well-known conventional method employed in the art of laser light scattering, using a Malvern Insitec L machine as supplied by Malvern Instruments Ltd (or by other methods which give essentially the same result).

[0090] Unless otherwise stated, particle size properties of the microfibrillated cellulose materials are measured by the well-known conventional method employed in the art of laser light scattering, using a Malvern Mastersizer S machine as supplied by Malvern Instruments Ltd (or by other methods which give essentially the same result). [0091] The fibrous substrate comprising cellulose maybe microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a d_5O ranging from about 5 pm to about 500 pm, as measured by laser light scattering.

The fibrous substrate comprising cellulose maybe microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a d_5O of equal to or less than about 400 pm, for example equal to or less than about 300 pm, or equal to or less than about 200 pm, or equal to or less than about 150 pm, or equal to or less than about 125 pm, or equal to or less than about 100 pm, or equal to or less than about 90 pm, or equal to or less than about 80 pm, or equal to or less than about 70 pm, or equal to or less than about 60 pm, or equal to or less than about 50 pm, or equal to or less than about 40 pm, or equal to or less than about 30 pm, or equal to or less than about 20 pm, or equal to or less than about 10 pm. [0092] The fibrous substrate comprising cellulose maybe microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a modal fibre particle size ranging from about 0.1-500 pm and a modal inorganic particulate material particle size ranging from about 0.25-20 pm. The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a modal fibre particle size of at least about 0.5 pm, for example at least about 10 pm, or at least about 50 pm, or at least about 100 pm, or at least about 150 pm, or at least about 200 pm, or at least about 300 pm, or at least about 400 pm. [0093] The fibrous substrate comprising cellulose maybe microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a fibre steepness equal to or greater than about 10, as measured by Malvern. Fibre steepness i.e., the steepness of the particle size distribution of the fibres) is determined by the following formula: Steepness = 100 x d_3O/d₇o)

[0094] The microfibrillated cellulose may have a fibre steepness equal to or less than about 100. The microfibrillated cellulose may have a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30. The microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.

[0095] The finer mineral peak can be fitted to the measured data points and subtracted mathematically from the distribution to leave the fibre peak, which can be converted to a cumulative distribution. Similarly, the fibre peak can be subtracted mathematically from the original distribution to leave the mineral peak, which can also be converted to a cumulative distribution. Both these cumulative curves may then be used to calculate the mean particle size (d_5O) and the steepness of the distribution (d₃o/d_7Q 100). The differential curve may then be used to find the modal particle size for both the mineral and fibre fraction

[0096] Another preferred inorganic particulate material for use is kaolin clay. The invention should not be construed as being limited to such embodiments. Thus, in some embodiments, kaolin is used in an unprocessed form.

[0097] Kaolin clay used in this invention maybe a processed material derived from a natural source, namely raw natural kaolin clay mineral. The processed kaolin clay may typically contain at least about 50% by weight kaolinite. For example, most commercially processed kaolin clays contain greater than about 75% by weight kaolinite and may contain greater than about 90%, in some cases greater than about 95% by weight of kaolinite.

[0098] Kaolin clay used in the present invention may be prepared from the raw natural kaolin clay mineral by one or more other processes which are well known to those skilled in the art, for example by known refining or beneficiation steps. [0099] For example, the clay mineral maybe bleached with a reductive bleaching agent, such as sodium hydrosulfite. If sodium hydrosulfite is used, the bleached clay mineral may optionally be dewatered, and optionally washed and again optionally dewatered, after the sodium hydrosulfite bleaching step.

[00100] The clay mineral may be treated to remove impurities, e.g. by flocculation, flotation, or magnetic separation techniques well known in the art.

Alternatively the clay mineral used in the invention may be untreated in the form of a solid or as an aqueous suspension.

[00101] The process for preparing the particulate kaolin clay for use in the present invention may also include one or more comminution steps, e.g., grinding or milling. Light comminution of a coarse kaolin is used to give suitable delamination thereof. The comminution may be carried out by use of beads or granules of a plastic (e.g. nylon), sand or ceramic grinding or milling aid. The coarse kaolin maybe refined to remove impurities and improve physical properties using well known procedures. The kaolin clay may be treated by a known particle size classification procedure, e.g., screening and centrifuging (or both), to obtain particles having a desired d₅₀ value or particle size distribution. [00102] Manufacturing Microfibrillated Cellulose

[00103] Prior art methods of manufacturing microfibrillated cellulose include mechanical disintegration by refining, milling, beating and homogenizing, and refining, for example, by an extruder. These mechanical measures may be enhanced by chemical or chemo-enzymatic treatments as a preliminary step. Various known methods of microfibrillation of cellulosic fibres are summarized in U.S. Pat. No. 6,602,994 Bi as including e.g. homogenization, steam explosion, pressurization-depressurization, impact, grinding, ultrasound, microwave explosion, milling and combinations of these. WO 2007/001229 discloses enzyme treatment and, as a method of choice, oxidation in the presence of a transition metal for turning cellulosic fibres to MFC. After the oxidation step the material is disintegrated by mechanical means. A combination of mechanical and chemical treatment can also be used. Examples of chemicals that can be used are those that either modify the cellulose fibers through a chemical reaction or those that modify the cellulose fibers via e.g. grafting or sorption of chemicals onto/into the fibers. [00104] Various methods of producing microfibrillated cellulose (“MFC”) are known in the art. Certain methods and compositions comprising microfibrillated cellulose produced by grinding procedures are described in WO-A-2010/ 131016. Husband, J. C., Svending, P., Skuse, D. R., Motsi, T., Likitalo, M., Coles, A., FiberLean Technologies Ltd., 2015, “Paper filler composition,” PCT International Application No. WO-A- 2010/131016. Paper products comprising such microfibrillated cellulose have been shown to exhibit excellent paper properties, such as paper burst and tensile strength. The methods described in WO-A-2010/131016 also enable the production of microfibrillated cellulose economically.

[00105] WO 2007/091942 Al describes a process, in which chemical pulp is first refined, then treated with one or more wood degrading enzymes, and finally homogenized to produce MFC as the final product. The consistency of the pulp is described to be preferably from about 0.4 to about 10%. The advantage is said to be avoidance of clogging in the high-pressure fluidizer or homogenizer.

[00106] W02010/131016 describes a grinding procedure for the production of microfibrillated cellulose with or without inorganic particulate material. Such a grinding procedure is described below. In an embodiment of the process set forth in WO-A-2010/131016, the contents of which is hereby incorporated by reference in its entirety, the process utilizes mechanical disintegration of cellulose fibres to produce microfibrillated cellulose (“MFC”) cost-effectively and at large scale, without requiring cellulose pre-treatment. An embodiment of the method uses stirred media detritor grinding technology, which disintegrates fibres into MFC by agitating grinding media beads. In this process, a mineral such as calcium carbonate or kaolin is added as a grinding aid, greatly reducing the energy required. Husband, J. C., Svending, P., Skuse, D. R., Motsi, T., Likitalo, M., Coles, A., FiberLean Technologies Ltd., 2015, “Paper filler composition,” U.S. Pat. US9127405B2. [00107] A stirred media mill consists of a rotating impeller that transfers kinetic energy to small grinding media beads, which grind down the charge via a combination of shear, compressive, and impact forces. A variety of grinding apparatus may be used to produce MFC by the disclosed methods herein, including, for example, a tower mill, a screened grinding mill, or a stirred media detritor. [00108] Homogenization preparation of microfibrillated cellulose

[00109] In some embodiments, microfibrillation of a fibrous substrate comprising cellulose maybe effected under wet conditions in the presence of the inorganic particulate material by a method in which the mixture of cellulose pulp and inorganic particulate material is pressurized (for example, to a pressure of about 500 bar) and then passed to a zone of lower pressure. The rate at which the mixture is passed to the low-pressure zone is sufficiently high and the pressure of the low pressure zone is sufficiently low to cause microfibrillation of the cellulose fibres. For example, the pressure drop maybe effected by forcing the mixture through an annular opening that has a narrow entrance orifice with a much larger exit orifice. The drastic decrease in pressure as the mixture accelerates into a larger volume (i.e., a lower pressure zone) induces cavitation which causes microfibrillation. In an embodiment, microfibrillation of the fibrous substrate comprising cellulose may be effected in a homogenizer under wet conditions in the presence of the inorganic particulate material. In the homogenizer, the cellulose pulp-inorganic particulate material mixture is pressurized (for example, to a pressure of about 500 bar), and forced through a small nozzle or orifice. The mixture maybe pressurized to a pressure of from about 100 to about 1000 bar, for example to a pressure of equal to or greater than about 300 bar, or equal to or greater than about 500, or equal to or greater than about 200 bar, or equal to or greater than about 700 bar. The homogenization subjects the fibres to high shear forces such that as the pressurized cellulose pulp exits the nozzle or orifice, cavitation causes microfibrillation of the cellulose fibres in the pulp. Water may be added to improve flowability of the suspension through the homogenizer. The resulting aqueous suspension comprising microfibrillated cellulose and inorganic particulate material maybe fed back into the inlet of the homogenizer for multiple passes through the homogenizer. In a preferred embodiment, the inorganic particulate material is a naturally platy mineral, such as kaolin. As such, homogenization not only facilitates microfibrillation of the cellulose pulp, but also facilitates delamination of the platy inorganic particulate material. [00110] A platy inorganic particulate material, such as kaolin, is understood to have a shape factor of at least about 10, for example, at least about 15, or at least about 20, or at least about 30, or at least about 40, or at least about 50, or at least about 60, or at least about 70, or at least about 80, or at least about 90, or at least about 100. Shape factor, as used herein, is a measure of the ratio of particle diameter to particle thickness for a population of particles of varying size and shape as measured using the electrical conductivity methods, apparatuses, and equations described in U.S. Patent No.

5,576,617, which is incorporated herein by reference

[00111] Optional components of the coating composition [00112] In some embodiments, the composition is formulated for use as an antimicrobial surface coating. In some embodiments, the composition is formulated for use as an antimicrobial surface coating capable of inactivating surface viability of microbes such as bacteria, viruses, and/or fungi.

[00113] In some embodiments, the composition comprises an inorganic particulate material. The inorganic particulate material, when present, may, for example, be an alkaline earth metal carbonate or sulphate, such as calcium carbonate, magnesium carbonate, dolomite, gypsum, a hydrous kandite clay such as kaolin, halloysite or ball clay, an anhydrous (calcined) kandite clay such as metakaolin or fully calcined kaolin, talc, mica, perlite or diatomaceous earth, or magnesium hydroxide, or aluminium trihydrate, graphene, graphene oxide, reduced graphene oxide, and mixtures thereof. [00114] In some embodiments, the composition comprises particles of silver, copper, copper oxide, bismuth, cobalt platinum, and mixtures thereof. In some embodiments, the size of the particles may be from 1 nm to 900 pm. In some embodiments, the particles are nanoparticles. In some embodiments, the particles are nanoparticles in the arrangement of core-shell nanoparticles. [00115] In some embodiments, the composition comprises microencapsulates that are liquid encapsulated in a shell. In some embodiments, the material for the shell can be either inorganic such as silicate particles or organic such as latex particles.

[00116] In some embodiments, the composition comprises Metal-Organic-Framework (MOF).

[00117] In some embodiments, the the composition comprises one or more hydrogels.

In some embodiments, the size of the hydrogel maybe from 1 nm to 900 pm. The hydrogel could be prepared using biopolymers such as chitosan, carrageenan, polylactide, or synthetic polymers. The hydrogels could carry stimuli-responsive components that can be triggered by light or humidity.

[00118] In some embodiments, the composition comprises a quaternary ammonium compound, such as benzalkonium chloride. In some embodiments, the composition comprises a single or multiple organic biocidal actives.

[00119] In some embodiments, the composition comprises functional additives such as fillers, cross-linkers, colorants, optical brightening agents, co-binders, or rheology modifiers, anti-foaming agents or foaming agents, biocides and/or anti-microbial agents.

[00120] Preparation of the coating composition

[00121] In some embodiments, the composition comprising microfibrillated cellulose is prepared by a process of: (i) obtaining a suspension of microfibrillated cellulose in a liquid component, for example water, (ii) adding one or more other liquids to the suspension from step (i) and optionally adding any further components, and optionally (iii) homogenizing the suspension obtained from step (ii).

[00122] Application of the coating [00123] In some embodiments, the composition is applied to the surface by spray- coating, spin-coating or may also be applied as a spot coating. In some embodiments, the composition is applied to the surface by spray-coating or spin-coating. In some embodiments, the coating is applied to the surface by spray-coating, optionally the spray-coating is applied for example, using a manual atomiser, an aerosol bottle or an industrial spray coater. [00124] In some embodiments, the coating can be applied in one or multiple layers. In some embodiments, the content of each layer applied to the surface may be identical or different in the different layers, i.e. different coating compositions maybe used for different layers.

[00125] In some embodiments, the coating can be applied in multiple layers by spray- coating, optionally the multiple layers are applied in about 1-100 sprays, or about 30-50 sprays. In some embodiments, the coating is applied to the surface by spray-coating using a manual atomiser. In some embodiments, the content of each layer sprayed onto the surface maybe identical or different in the different layers, i.e. different coating compositions maybe used for different layers. [00126] Typically, the coating composition that is applied to a surface of an article dries quickly. In some embodiments, the drying time of the coating is in the range of from about 1 s to about 60 s. Such a drying time may avoid bubbles and leads to a surface with optimal surface characteristics.

[00127] When applied to the target surface of an article, the disclosed compositions may form a strong external barrier after drying. In some embodiments, the compositions maybe dried to form the coating by allowing the liquid in the composition to evaporate optionally at room temperature. In some embodiments, the coating is dried using heat to facilitate faster drying of the composition optionally thereby preventing or mitigating long-term exposure to oxygen and light. In some embodiments, temperatures ranging from about 3O°C to about 35°C can be used to dry the compositions after they have been applied to a surface. In some embodiments, a hot air drying technique can be used to dry (at least partially) the coating. Such hot air drying techniques can use temperatures ranging from about 6o°C to about 9O°C for a time period ranging from about 2 minutes to about 10 minutes.

[00128] In some embodiments, the compositions may be dried to form the coating by allowing the liquid in the composition to evaporate at a temperature of less than about 200 °C, or less than about 150 °C, or less than about 100 °C, or less than about 50 °C or less than about 40 °C. In some embodiments, the compositions maybe dried to form the coating by allowing the liquid in the composition to evaporate at a temperature less than about 3O°C.

[00129] In some embodiments, the compositions may be dried to form the coating by allowing the liquid in the composition to evaporate at room temperature. As used herein ‘room temperature’ may refer to a temperature of about 15-25°C. This provides several advantages over use of elevated temperature for instance special apparatus to maintain the drying at an elevated temperature is not required, making a process at room temperature more practical. Alternatively, the compositions maybe dried to form the coating by allowing the liquid in the composition to evaporate at a temperature of about O"3O°C, or about o-i5°C, or about 25-3O°C.

[00130] Coating

[00131] In some embodiments, the coating is an antimicrobial surface coating. In some embodiments, the coating is an antiviral surface coating. [00132] In some embodiments, the coating is obtained in the form of a thin layer comprising microfibrillated cellulose. In some embodiments, the coating is obtained in the form of a film comprising microfibrillated cellulose.

[00133] In some embodiments, the coating has a thickness of between about 50 and about 5000 nm. In some embodiments, the coating has a thickness of between about 50 and about 2000 nm. In some embodiments, the coating has a thickness of between about 100 and about 1500 nm. In some embodiments, the coating has a thickness of between about 100 and about 1000 nm. In some embodiments, the coating has a thickness of between about 100 and about 500 nm.

[00134] In some embodiments, the coating has a thickness of less than about 5000 nm. In some embodiments, the coating has a thickness of less than about 2000 nm. In some embodiments, the coating has a thickness of less than about 1500 nm. In some embodiments, the coating has a thickness of less than about 1300 nm.

[00135] In some embodiments, the coating is invisible. As used herein, the term ‘invisible’ refers to the inability for an individual to readily see the coating with the naked eye. In some embodiments, the coating is unnoticeable to the naked eye. In some embodiments, the coating has an opacity of less than about 10%, for example less than about 8%, less than about 5% or less than about 2% (e.g. as measured by an opacimeter or a spectrophotometer).

[00136] In some embodiments, the coating comprises microfibrillated cellulose in an amount of about 80 to about 100 wt% based on the total weight of the coating. In some embodiments, the coating comprises microfibrillated cellulose in an amount of about

90 to about 100 wt% based on the total weight of the coating. In some embodiments, the coating comprises microfibrillated cellulose in an amount of about 95 to about 100 wt% based on the total weight of the coating. In some embodiments, the coating comprises microfibrillated cellulose in an amount of about 99 to about 100 wt% based on the total weight of the coating. In some embodiments, the coating consists essentially of microfibrillated cellulose.

[00137] In some embodiments, the microfibrillated cellulose content of the coating maybe in the range of from about 0.01 to about 99.9 wt% based on the weight of solids of the coating. In some embodiments, the microfibrillated cellulose content of the coating layer may be in the range of about 70 to about 99 wt%, in the range of about 80 to about 99 wt%, or in the range of from about 90 to about 99 wt% based on the weight of the solids of the coating. [00138] In some embodiments, the coating has a surface porosity of between about 20-70 % (of total surface area). In some embodiments, the coating has a porosity of between about 25-65 %.

[00139] In some embodiments, the coating has a mean pore size of between about 2-20 pm. In some embodiments, the coating has a mean pore size of between about 4-12 pm.

[00140] The surface porosity and mean pore size may be measured using a scanning electron microscope (e.g. Philips XL-30 FEG ESEM). Porosity levels can be evaluated using the image processing program (e.g. Gwyddion and the integrated Watershed algorithm). [00141] In some embodiments, the water contact angle of the coating is between about o° and 180°. In some embodiments, the water contact angle of the coating is between about o° and 90°. In some embodiments, the water contact angle of the coating is between about io° and 90°. In some embodiments, the water contact angle of the coating is between about io° and 45⁰. In some embodiments, the water contact angle of the coating is about 40° or less. In some embodiments, the water contact angle of the coating is about 35⁰ or less. In some embodiments, the water contact angle of the coating is about 30° or less.

[00142] In some embodiments, the water contact angle (°) of the coating is at least about 50% lower than the water contact angle of a corresponding untreated surface. [00143] The water contact angle of the coating maybe measured using a generic contact angle goniometer (Ossila Ltd.).

[00144] In some embodiments, the coating has a roughness (R_a) of between about 50 - 400 nm. In some embodiments, the coating has a roughness (R_a) of between about 5 - 200 nm. In some embodiments, the coating has a roughness (R_a) of between about 200 - 2000 nm.

[00145] In some embodiments, the coating has a waviness (W_a) of between about 100

- 700 nm. [00146] The coating roughness and waviness maybe measured using an atomic force microscope (AFM, Multimode, Broker) with a tapping mode cantilever (NCHR-20, Apex Probes Ltd.). Surface parameters maybe extracted from the scans by the AFM and a white light interferometer (WLI). [00147] The term ‘coating’ as used herein refers to a layer of the composition created on the surface of an article. The layer need not have a uniform thickness or be completely homogenous in composition. Also, the coating need not cover the entire article to which it is applied. In some embodiments, the coating can substantially coat the article. In such embodiments, the coating can cover about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the surface area of the article. In other embodiments, the coating can completely coat the article - that is it can cover about 100% of the object. In some embodiments, the coating can have a thickness that varies by about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% over the article.

[00148] Coating removal [00149] In some embodiments, the method comprises a step of removing the coating from the surface. In some embodiments, the method comprises a step of the removing the coating from the surface by applying water to the coating.

[00150] In some embodiments, the coating is removable from the surface. In some embodiments, the coating is removable from the surface by the application of water to the coating.

[00151] Surfaces and products

[00152] In some embodiments, the coating may be applied to one or more surfaces of an article.

[00153] In some embodiments, the surface to be treated is non-porous, i.e. the surface is a non-porous surface. [00154] In some embodiments, the surface to be treated is hard, i.e. the surface is a hard surface.

[00155] In some embodiments, the surface to be treated is selected from the group consisting of glass, ceramic, wood, metal, paint, plastic and mixtures thereof. In some embodiments, the surface to be treated is selected from the group consisting of glass, ceramic, wood, metal and mixtures thereof. In some embodiments, the surface to be treated may itself be a coating on a surface.

[00156] Many surfaces exposed to repeated human contact will benefit from the application of compositions comprising microfibrillated cellulose of the present invention. The surface coating compositions of the present invention will target the public transport sector, including aviation, rail and buses where surfaces are believed to bear high concentrations of viral -laden aerosols, particularly in confined spaces within the foregoing transportation means. The compositions will also be targeted to treat surfaces in medical, business, educational and household settings. For example, the surface coating compositions of the present invention will target surfaces in areas with a high traffic population.

[00157] In some embodiments, the surface is a high-touch surface such as counters, shopping carts, table tops, doorknobs, light switches, handles, stair rails, elevator buttons, desks, keyboards, phones, toilets, faucets, and sinks. [00158] Further definitions

[00159] The titles, headings and subheadings provided herein should not be interpreted as limiting the various aspects of the disclosure. Accordingly, the terms defined below are more fully defined by reference to the specification in its entirety. All references cited herein are incorporated by reference in their entirety. [00160] Unless otherwise defined, scientific and technical terms used herein shall have the meanings that are commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.

[00161] In this application, the use of “or” means “and/or” unless stated otherwise. In the context of a multiple dependent claim, the use of “or” refers back to more than one preceding independent or dependent claim in the alternative only.

[00162] It is further noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” and any singular use of any word, include plural referents unless expressly and unequivocally limited to one referent.

[00163] The instant invention is most clearly understood with reference to the following definitions.

[00164] The term "about" is used herein to mean approximately, in the region of, roughly, or around. When the term "about" is used in conjunction with a numerical range, it modifies that range by extending the boundaries above and below the numerical values set forth. In general, the term "about" is used herein to modify a numerical value above and below the stated value by a variance of io%.

[00165] As used herein, the terms "comprising" (and any form of comprising, such as "comprise", "comprises", and "comprised"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include"), or "containing" (and any form of containing, such as "contains" and "contain"), are inclusive or open-ended and do not exclude additional, unrecited elements or method steps. Additionally, a term that is used in conjunction with the term "comprising" is also understood to be able to be used in conjunction with the term "consisting of or "consisting essentially of."

[00166] The term "dry" weight is intended to mean the weight of the composition free of liquid, in particular free of water. [00167] As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

[00168] As used herein, the phrase "integer from X to Y" means any integer that includes the endpoints. For example, the phrase "integer from i to 5" means 1, 2, 3, 4, or 5.

[00169] The term “recycled cellulose-containing materials” means recycled pulp or a papermill broke and/or industrial waste, or paper streams rich in mineral fillers and cellulosic materials from a papermill. [00170] For the avoidance of doubt, insofar as is practicable any embodiment of a given aspect of the present invention may occur in combination with any other embodiment of the same aspect of the present invention. In addition, insofar as is practicable it is to be understood that any preferred or optional embodiment of any aspect of the present invention should also be considered as a preferred or optional embodiment of any other aspect of the present invention.

[00171] The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. Also, the description of the embodiments of the present invention is intended to be illustrative and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art.

[00172] It is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.

[00173] The various embodiments described in this specification can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.

[00174] The disclosures of each and every patent, patent application, publication, and accession number cited herein are hereby incorporated herein by reference in their entirety.

[00175] While the present disclosure has been disclosed with reference to various embodiments, it is apparent that other embodiments and variations of these maybe devised by others skilled in the art without departing from the true spirit and scope of the disclosure. The appended claims are intended to be construed to include all such embodiments and equivalent variations. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure. [00176] The foregoing written specification is considered to be sufficient to enable one skilled in the art to practice the embodiments. The foregoing description and Examples detail certain embodiments and describes the best mode contemplated by the inventors. It will be appreciated, however, that no matter how detailed the foregoing may appear in text, the embodiment may be practiced in many ways and should be construed in accordance with the appended claims and any equivalents thereof.

EXAMPLES

[00177] Materials

[00178] A micro fibrillated cellulose (MFC) aqueous slurry (solid content 0.7 wt.%, 99.9 % of the solid content is cellulose, batch code FLD0216-200051) was obtained from Fiberlean Technologies Ltd. UK. The MFC was fiber/ fibril only MFC. [00179] Polyethyleneimine (PEI; Product code 181978) was obtained from Sigma- Aldrich.

[00180] Phosphate buffered saline (PBS; P4417) was obtained from Sigma-Aldrich.

[00181] Mucin (Type I-S from bovine submaxillary glands; M3895) was obtained from Sigma-Aldrich.

[00182] Bovine Serum Albumin (BSA; A9647) was obtained from Sigma-Aldrich.

[00183] Tryptone (T9410) was obtained from Sigma-Aldrich.

[00184] Fluorescence dye Alexa Fluor™ 488 C5 Maleimide was obtained from ThermoFisher Scientific. [00185] Glass coverslips ( <X> 10 mm, thickness 0.16-0.19 mm) were obtained from

Fisher Scientific.

[00186] Artificial skin (polyurethane elastomer).

[00187] Thin Film Fabrication

[00188] Glass coverslips (O 10 mm, thickness 0.16-0.19 mm) were cleaned with ethanol and then placed within an oxygen plasma chamber (HPT-1OO, by Henniker Plasma) for 5 minutes. 70 pl polyethyleneimine solution (1% w/v in H₂0) was placed on the cleaned glass coverslips which were spun at 600 rpm for 30 seconds on a spin coater (SPIN 150!, APT GmbH), then accelerated at 500 rpm/s to 4000 rpm and spun for 60 seconds to provide pre-treated glass coverslips. [00189] MFC thin films were fabricated on the pre-treated glass coverslips using two different approaches, namely spin-coating and spray-coating. The MFC aqueous slurry was diluted with ethanol (v/v = 1:5) and homogenised (using a SHM1 homogeniser, Stuart) for 3 minutes before use to provide an MFC suspension. In the case of spin coating, 400 pl MFC suspension was added dropwise onto a pre-treated glass coverslip spinning at 6000 rpm. In the case of spray coating, a manual cosmetic atomiser (Avalon, 30mL, spray dosage o.i6mL) was used to apply the MFC suspension onto a stationary pre-treated glass coverslip. 40 sprays were made to obtain a high percentage of coverage on the pre-treated surface.

[00190] Artificial Salvia Preparation

[00191] An artificial salvia solution was prepared in compliance with international standard ASTM E2197 and formed of three types of proteins (i) high molecular weight proteins (Bovine Serum Albumin, BSA), (ii) low molecular weight peptides (tryptone), and (iii) mucous material (mucin).

[00192] To prepare the artificial saliva solution, the following solutions were individually prepared: (i) 0.5 g BSA in 10 mL PBS; (ii) 0.5 g tryptone in 10 mL PBS; and (iii) 0.04 g mucin in 10 mL PBS. Each of solutions (i) to (iii) were then passed through a 0.22 pm pore diameter membrane filter, divided into aliquots, and stored at either 4 ± 2°C (for storage under 24 hours) or -20 ± 2°C (for storage over 24 hours, followed by thawing before use). 500 pL of the artificial saliva solution was obtained by mixing 25 pL of solution (i), 35 pL of solution (ii), 100 pL of solution (iii), and 340 pL PBS in a container (mixed using a magnetic stirrer for 30 minutes). The concentration of mucin in the resulting artificial saliva solution was 0.8 mg/ml.

[00193] Thin Film Characterisation

[00194] Surface morphology of the thin films was examined using an atomic force microscope (AFM, Multimode, Bruker) with a tapping mode cantilever (NCHR-20, Apex Probes Ltd.) and a scanning electron microscope (Philips XL-30 FEG ESEM).

Surface parameters were extracted from the scans by the AFM and a white light interferometer (WLI). Porosity levels of the thin films were evaluated semi- quantitatively using the image processing program Gwyddion and the integrated Watershed algorithm. [00195] Figure 1A is an optical microscopic (Leica Z16 APOA) image of an MFC thin film prepared by the herein described spin-coating method. [00196] Figure 1B is an optical microscopic image of an MFC thin film prepared by the herein described spray-coating method.

[00197] Figure 1C is an atomic force microscopic image of an MFC thin film prepared by the herein described spin-coating method. [00198] Figure 1D is an atomic force microscopic image of an MFC thin film prepared by the herein described spray-coating method.

[00199] Figure 1E is a scanning electron microscopic image of an MFC thin film prepared by the herein described spin-coating method.

[00200] Figure 1F is a scanning electron microscopic image of an MFC thin film prepared by the herein described spray-coating method.

[00201] As shown in figures 1A to 1F, the spray-coating and spin-coating methods both resulted in a good coverage on the pre-treated glass coverslip whilst the density of MFC colonies on the spin-coated MFC thin films is slightly higher than that of those MFC films fabricated by spray-coating. The spin-coated MFC thin films also demonstrate a marginal yet discernible preferred orientation of the fibrils along the radius of the substrate due to the centrifugal effect during spinning. As a comparison, the spray- coated MFC thin films show a more random distribution of the cellulose fibrils.

[00202] Figure 2A shows the height distribution of MFC thin films prepared by the herein described spin-coating method and spray-coating method which suggest that the spray-coated MFC thin films and the spin-coated MFC thin films were 300 nm and 1.2 pm thick, respectively, rendering them effectively invisible to the human eye (see

Figure 2B).

[00203] Surface parameters such as roughness, waviness and porosity were extracted from surface profile scans and are summarised in Table 1. Table i

[00204] As shown in Table 1, the spin-coated MFC thin films were measured to have a rougher topography, but a lower mean pore size compared to the spray-coated MFC thin films, implying that the former should possess a larger surface area within the MFC architecture.

[00205] The surface parameters of the MFC thin films can be tuned according to the sample preparation methods. For example, a series of spin-coated MFC thin films were prepared according to the above-described spin-coating method except that the spin speed and amount of MFC suspension was varied. The surface roughness of the spin- coated MFC thin films decreased when the spin speed increased (Figure 3A).The porosity increased monotonically as a function of the spin speed (figures 3A and 3B).

Applying more MFC suspension (200 pl vs. 400 pl) onto the spinning substrate led to higher surface roughness and lower porosity levels (figures 3A and 3B).

[00206] Example 1: MFC Thin Film Mechanical Stability

[00207] The mechanical stability of the spin coated MFC thin films were evaluated by means of scraping tests against artificial skin using the following methodology. For each of the following tests, an artificial skin piece was fixed on one end of an instrument arm. The artificial skin piece was brought into contact with an MFC thin film and pushed laterally across the MFC thin film with the contact force being kept at either 2 N or 4 N. The distance over which the arm of the force board moved is 25 mm with a speed of 10 mm/s. Figures 4A to 4E show the results of the scraping tests using a contact force of 2N. Similar results were obtained using a contact force of 4N.

[00208] The first test used a single pass of the artificial skin piece on a dry (i.e. not pre- wetted) MFC thin film. See Figure 4A which is an optical microscopic image of the MFC thin film before the first test and Figure 4B showing the same MFC thin film after the first test.

[00209] The second test used 17 passes of the artificial skin piece on a dry (i.e. not pre- wetted) MFC thin film. See Figure 4C which is an optical microscopic image of the MFC thin film before the second test and Figure 4D showing the same MFC thin film after the second test.

[00210] The third test used a single pass of the artificial skin piece on an MFC thin film that had been pre-wetted with artificial saliva droplets (by placing a 0.5 pl droplet of artificial salvia on the film immediately before the test). See Figure 4E which is an optical microscopic image of the MFC thin film before the third test and Figure 4F showing the same MFC thin film after the third test.

[00211] The morphology of the MFC thin films did not show noticeable removal after the scraping tests with a 2 N load under dry conditions (i.e. for the not pre-wetted MFC thin films), even after multiple cycles of the lateral scraping. The good mechanical stability of the thin film is assigned to the hydrogen bonding between cellulose fibrils and at the cellulose-substrate interface that sufficiently immobilise the network of cellulose fibrils and gives rise to its considerable resistance to occasional scratches while it is dry. However, the MFC thin film was easily removed within a single scraping when it was wetted (only the area of the MFC thin film that had been pre-wetted was removed, the remaining non-wetted area was not removed). The results show that the MFC thin films can be fabricated on common communal surfaces by simply spraying whilst showing good durability in dry, ambient conditions. They can also be removed easily when wetted and re-applied wherever needed during everyday cleaning procedures.

[00212] Example 2.1: Goniometry

[00213] For each of the following examples, contact angle measurements were carried out against a droplet size 1 mm in diameter (0.5 pl in volume), for which a generic contact angle goniometer (Ossila Ltd.) was employed.

[00214] In example 2.1, a 1 mm diameter water droplet was deposited on a pre-cleaned (uncoated) glass coverslip, a spray-coated MFC thin film, and a spin-coated MFC thin film. The water contact angles (dynamic contact angles) were measured 200 milliseconds after deposition of the 1 mm diameter water droplets. The results are shown in Figure 5A. Additionally, the time until the droplets stopped being discernible to the optics of the goniometer was measured. The results are shown in Figure 5B.

[00215] Figure 5A shows that MFC thin films fabricated by spray-coating and spin- coating result in significantly reduced contact angles relative to the uncoated glass coverslips (approximately around a half and a third of the contact angle on the uncoated glass coverslip, respectively). This is attributed to the hydrophilic and thus more wettable surface of the MFC.

[00216] Figure 5B shows the time periods during which the droplets were present on the surface (the uncoated glass coverslip, the spray-coated MFC thin film, and the spin- coated MFC thin film) and discernible to the optics of the goniometers. Droplets on solid, flat surfaces (such as the uncoated glass coverslips) simply evaporate over time, whilst droplets deposited on such porous surfaces as the MFC thin films also undergo quick spreading and penetration upon landing. As shown in Figure 5B, shows that a 1 mm diameter droplet remained detectable for more than 8 minutes (498 seconds) on the uncoated glass coverslip until complete evaporation. In contrast, a 1 mm diameter droplet remained detectable for only approximately 3 minutes (195 seconds) and 2 minutes (110 seconds) on the spray-coated MFC thin film and the spin-coated MFC thin film, respectively. This remarkable reduction demonstrates the MFC thin films can effectively shorten the existing time of aqueous droplets on the surface, hence largely reducing the likelihood foreign surfaces are contaminated by touching the droplet site.. [00217] Example 2.2 QCM Evaporation [00218] The evaporation behavior of droplets of deionized water and the artificial saliva solution were studied using silicon dioxide coated quartz crystal microbalance (QCM) sensors (5 MHz 14 mm Cr/Au/Si02, Quartz Pro, Sweden). For each of examples 2.2.1 to 2.2.4, the surface of the QCM sensor was (i) the crystal sensor pre-treated in the same way as the above glass coverslips (pre-treated sensor surface); (ii) a spray-coated MFC thin film on a pre-treated sensor surface, or (iii) a spin-coated MFC thin film on a pre-treated sensor surface. The spin-coated MFC thin film and spray-coated MFC thin film were applied to the pre-treated sensor surfaces in the same way that they were applied to the glass coverslips (see Thin Film Fabrication above).

[00219] In example 2.2.1, a deionised water droplet of 1 mm in diameter was generated and placed onto each of the QCM sensor surfaces (i) to (iii) by a micropipette.

[00220] In example 2.2.2, a droplet of the artificial saliva solution of 1 mm in diameter was generated and placed onto each of the QCM sensor surfaces (i) to (iii) by a micropipette.

[00221] In example 2.2.3, aerosol droplets of deionised water (3.0 pm, mass median aerodynamic diameter) were generated and deposited on each of the QCM sensor surfaces (i) to (iii) using a commercially available nebuliser (Omron C28P). The aerosolised droplets were breathed out towards the QCM sensor from a distance of approximately 5 cm at a nebulisation rate of 0.5 mL/min. The duration of each aerosol spit was fixed to be 5 seconds to stimulate sufficient response from the QCM. [00222] In example 2.2.4, aerosol droplets of the artificial saliva solution were generated and deposited each of the QCM sensor surfaces (i) to (iii) using the nubulizer as described in example 2.2.3. [00223] The frequency history of the quartz sensors was recorded throughout the deposition and evaporation of the droplets in examples 2.2.1 to 2.2.4 using a QCM quartz crystal microbalance (openQCM NEXT, Italy). The quartz crystal sensor, upon an applied voltage, is excited to oscillate at its resonance frequency f_o. The resonant frequency will decrease as a consequence of an adsorbed molecular layer on the crystal surface. Therefore, by looking at the frequency history over time it is possible to identify the moment a droplet was placed on the quartz crystal (frequency dipped) and dried out (frequency recovered). The results are shown in figures 6 to 9 (examples 2.2.1 to 2.2.4, respectively). [00224] Figure 6 shows the the typical evaporation behaviours of 1 mm diameter water droplets on sensor surfaces (i) to (iii). The frequency shift 4f of sensor surface (i) in response to the evaporating water droplet demonstrated three distinct stages: an instant decrease in/from its fundamental value (4f= 100 Hz) when the water droplet is deposited; a plateau of a few minutes during which 4f is relatively constant; a gradual and steady recovery of /up to its original unloaded value (4f = o Hz), indicating the completi on of the evaporation. The evaporation events on sensor surface (i) last approximately 10 min.

[00225] 4f in examples 2.2.1 to 2.2.4 is majorly a measure of the interactions at the solid-liquid interface rather than the total mass change of the spherical cap on top. The second stage of the evaporation on sensor surface (i), where 4f keeps effectively constant, is interpreted as evaporating in the so-called constant contact radius mode. During this stage the contact line is pinned whilst the contact angle and the droplet height decrease as the evaporation continues. The constant contact radius mode lasts until the pinning force, which is a cosine function of the contact angle, is no longer strong enough and the contact line starts to contract, steering the evaporation into the final stage, i.e. a constant contact angle or a mixed mode and resulting in a gradual recovery of the resonant frequency/. [00226] Figure 6 (example 2.2.1) shows that the ramped recovery of/ (due to a largely linear reduction in contact area) on sensor surface (i) was completely cancelled for both sensor surfaces (ii) and (iii). Instead, Af for sensor surfaces (ii) and (iii) remained unchanged throughout (after the initial decrease) until an abrupt recovery to their unloaded values at the end of the evaporation. This change in the frequency evolution indicates that the contact areas of the 1 mm water droplets on sensor surfaces (ii) and (iii) were effectively constant over their life span. This is ascribed to the MFC thin films that are much more wettable owing to the natural hydrophilicity of the cellulose fibrils and the highly porous structure they form. Meanwhile, the higher surface roughness levels of the MFC thin films (~ioo nm for the spray-coated MFC thin film and -250 nm for the spin-coated MFC thin film) gives rise to a larger contact angle hysteresis and complete contact line pinning compared to the uncoated sensor surface.

[00227] The MFC thin film coated sensors manifested enormously amplified response (4fioo Hz, 700 Hz and 5 kHz for sensor surfaces (i), (ii), and (iii) respectively) to the droplets of the same size. This significantly increased sensitivity to adsorbed mass can also to attributed to the surface roughness introduced by the MFC thin films.

[00228] Importantly, Figure 6 shows that the present MFC thin films shortened the lifetime of 1 mm water drops significantly from around 10 minutes to 3-5 min irrespective of the coating approach. This is understood to be because the water droplets were pinned longer, and their surface area stayed large longer due to the increased surface hydrophilicity, resulting in less time needed for complete evaporation.

[00229] Figure 7 (example 2.2.2) shows the the typical evaporation behaviours of 1 mm diameter artificial saliva droplets on sensor surfaces (i) to (iii). In contrast to Figure 6, a full recovery to the fundamental frequency is not shown for any of sensor surfaces (i) to

(iii). This is because the non-volatile ingredients of the artificial saliva, including mucin proteins and inorganic salt species tend to diffuse towards the three-phase interface and adhere inevitably to the surface at the end of the evaporation. The adsorbed matter finally remaining on the surface upon full dryness is formed of mucin and salt nuclei.

As a consequence, the final frequency shifts Affinal upon complete evaporation were similar irrespective of surface configuration (Affinal 1600, 1350, 1400 Hz for sensor surfaces (i) to (iii), respectively).

[00230] Similar to example 2.2.1, the evaporation of artificial saliva drops on sensor surface (i) in Figure 7 shows an initial frequency drop due to the creation of a new solid-liquid interface covering part of the surface area. It is followed by an incubation period of about 6 min as discussed above for the water evaporation in example 2.2.1. The relatively flat A/ suggests that the interfacial adsorption is so far predominated by a water film and the deposition and adsorption of other components (mucin proteins and salts) is negligible at this stage. The frequency then meets the second knee point and turns down gradually when the proteins and salts start to approach the crystal surface.

In the finishing stage of the evaporation, the final amount of water is dried out within a short period of time. The mucin and salt masses are pulled down towards the quartz surface by the capillary forces of the evaporating water, causing a rapid decrease in/ before stabilising at its final level, i.e., when evaporation completes.

[00231] Figure 7 shows that for both sensor surface (ii) and (iii), the total evaporation time is reduced by over 50%. The time taken for the artificial saliva droplets to dry out remained essentially at the same scale as the water droplets drying on the same surfaces (as in example 2.2.1). Water evaporation is therefore limiting the lifetime of the artificial saliva droplets. The MFC thin films were effective in accelerating the water evaporation as discussed in relation to example 2.2.1.

[00232] Examples 2.2.3 and 2.2.4 represent dynamic aerosol drying processes. Unlike the 1 mm diameter droplet evaporation in examples 2.2.1 and 2.2.2, all the QCM sensor surfaces show ‘V’ shaped responses (see Figures 8 and 9), and no period over which A/ is flat is observed, indicating that no contact line pinning stages occurred. The Af of all sensor surfaces (i) to (iii) were found ever changing. It is important to note that in examples 2.2.3 and 2.2.4, instead of one single drop (as in examples 2.2.1 and 2.2.2), a large number of aerosolised droplets land on and evaporate from the surfaces over the

5 seconds. Condensation of the aerosolised droplets can also occur at the target substrate given the continuous aerosol flow.

[00233] Figures 8 and 9 show that the evaporation events on sensor surface (ii) and (iii) last three to four times longer compared to those on sensor surface (i). The longer evaporation time on the MFC coated sensor surfaces is believed to because of the porous structure and increased surface area that leads to a higher uptake of the aerosolised droplets. The aerosolised droplets deployed were effectively smaller than the pore sizes of the spray-coated MFC thin film and the spin-coated MFC thin film (around 10 and 5.8 pm respectively). The MFC films thus trapped more aerosol droplets from the nebulizer, which contributes to their longer evaporation time. This shows that the present MFC thin films are effective in capturing and immobilising free- flight aerosols, including those of respiratory fluid, granting them a high potential towards hygiene and healthcare applications.

[00234] Example s: Contact Transfer Evaluation

[00235] The ability of the MFC thin films to reduce the contact transfer from a surface to a person was evaluated by means of touch tests using artificial skin using the following methodology. For each of the following touch tests, an artificial skin piece was fixed on one end of an instrument arm. The artificial skin piece was driven smoothly towards and into contact with an MFC thin film or pre-treated glass coverslip until a contact force of 2 N was reached. The artificial skin was retracted from the MFC thin film or uncoated glass coverslip smoothly. Each touch cycle lasted approximately 5 seconds.

[00236] For each of the following tests, a fluorescent dye (Alexa Fluor 488) was introduced to the artificial saliva . [00237] In example 3.1, a droplet of the fluorescent dye stained artificial saliva solution was deposited on a uncoated glass coverslip. The uncoated glass coverslip loaded with the droplet was immediately subjected to the above touch test.

[00238] In example 3.2, a droplet of the fluorescent dye stained artificial saliva solution was deposited on a spray-coated MFC thin film. The MFC thin film loaded with the droplet was immediately subjected to the above touch test.

[00239] In example 3.3, a droplet of the fluorescent dye stained artificial saliva solution was deposited on a spin-coated MFC thin film. The MFC thin film loaded with the droplet was immediately subjected to the above touch test. [00240] In example 3.4, a droplet of the fluorescent dye stained artificial saliva solution was deposited on a uncoated glass coverslip. The pre-treated glass coverslip loaded with the droplet was subjected to the above touch test 5 minutes after the droplet was applied to the uncoated glass coverslip.

[00241] In example 3.5, a droplet of the fluorescent dye stained artificial saliva solution was deposited on a spray-coated MFC thin film. The MFC thin film loaded with the droplet was subjected to the above touch test 5 minutes after the droplet was applied to the MFC thin film.

[00242] In example 3.6, a droplet of the fluorescent dye stained artificial saliva solution was deposited on a spin-coated MFC thin film. The MFC thin film loaded with the droplet was subjected to the above touch test 5 minutes after the droplet was applied to the MFC thin film.

[00243] Examples 3.7, 3.8, and 3.9 were conducted using the same methodology as in examples 3.1, 3.2 and 3.3 except that instead of a droplet of the fluorescent dye stained artificial saliva solution, droplets of aerosol (3.0 pm, mass median aerodynamic diameter) of the solution was deposited using a nebulizer (Omron C28P) pointed at the

MFC thin film or uncoated glass coverslip from a distance of 5 cm (the nebulizer was turned on for a period of 30 seconds at a nebulization rate of 0.5 mL/min). [00244] Examples 3.10, 3.11, and 3.12 were conducted using the same methodology as in examples 3.4, 3.5 and 3.6 except that instead of a droplet of the fluorescent dye stained artificial saliva solution, droplets of aerosol (3.0 pm, mass median aerodynamic diameter) of the solution was deposited using a nebulizer (Omron C28P) pointed at the MFC thin film or uncoated glass coverslip from a distance of 5 cm (the nebulizer was turned on for a period of 30 seconds at a nebulization rate of 0.5 mL/min).

[00245] For each of examples 3.1 to 3.9, the MFC thin film/ uncoated glass coverslip before the touch test, the MFC thin film/glass coverslip after the touch test and the artificial skin after the touch test were imaged (using a fluorescent microscope: Leica Z16 APOA; 470 nm excitation wavelength). The areas of the fluorescent protein stains after the touch were recorded and analysed using the image processing programme Imaged and the results are shown in Figures 10 to 14.

[00246] Figure 10 shows the redistribution of 1 mm diameter artificial saliva droplets on a substrate (uncoated glass coverslip, spray-coated MFC thin film, or spin-coated MFC thin film) before and after the touch test in examples 3.1, 3.2 and 3.3 as well as the artificial skin after said touch tests.

[00247] Figure 11 shows the redistribution of 1 mm diameter artificial saliva droplets on a substrate (uncoated glass coverslip, spray-coated MFC thin film, or spin-coated MFC thin film) before and after the touch test in examples 3.4, 3.5 and 3.6 as well as the artificial skin after said touch tests.

[00248] Figure 12 shows the redistribution of 1 mm diameter artificial saliva droplets on a substrate (uncoated glass coverslip, spray coated MFC thin film, or spin coated MFC thin film) before and after the touch test in examples 3.7, 3.8 and 3.9 as well as the artificial skin after said touch tests. [00249] Figure 13 shows the area of fluorescent stained mucin on the artificial skin following the touch tests in examples 3.1 to 3.6. Figure 14 shows the area of fluorescent stained mucin on the artificial skin following the touch tests in examples 3.7 to 3.12. [00250] By counting and comparing the areas of artificial skin showing a fluorescent response after contact with the artificial saliva solution on (i) a uncoated glass coverslip; (ii) a spray-coated MFC thin film; and (iii) a spin-coated thin film (figures io to 14), it is clearly evidenced that both the spin-coated and spray-coated MFC thin films suppress cross contamination via the back transfer of the mucin (i.e. potentially virus containing) to other surfaces.

[00251] Figure 10 and Figure 13 show that the spray coated MFC thin film and the spin coated MFC thin film spread the artificial saliva droplets instantly to areas approximately 200% and 400% of that of the same droplet on the uncoated glass coverslip, respectively. The circular droplet on the uncoated glass coverslip was smeared by the artificial skin and left an intense and large area of fluorescence signal on the artificial skin, indicating that a large amount of mucin was collected by the artificial skin during the touch time of 5 seconds. The fluorescence on the artificial skin pieces after pressing against the spray coated MFC thin film and the spin coated MFC thin film attenuated significantly in both intensity and area (an up to 90% reduction in area) relative to the uncoated glass coverslip.

[00252] Figure 11 and Figure 13 show the transfer of mucin upon contact that was made 5 min after the droplet deposition. The fluorescence on the artificial skin pieces after touching the spray coated MFC thin film and the spin coated MFC thin film attenuated significantly in both intensity and area relative to the uncoated glass coverslip. The artificial skin piece was heavily soiled after touching the uncoated glass coverslip. This is in sharp contrast to the MFC thin films that passed negligible mucin stains onto the artificial skin following the touch test when the droplets were left on for 5 min. [00253] Figure 12 and Figure 14 show that the transfer of mucin from the MFC thin films, pre-loaded with artificial saliva aerosol sprays, to the artificial skin is almost zero following the touch tests of examples 3.8, 3.9, 3.11 and 3.12. In contrast, the artificial skin showed large amounts of mucin following contact with the uncoated glass coverside in examples 3.7 and 3.10.

[00254] Example 4: Antimicrobial testing

[00255] In example 4.1, the MFC thin films’ ability to inhibit surface transmission of SARS-C0V-2 was studied through in vitro infection of Vero cells. To replicate virus droplets as in a sneeze from an infected person, 0.5 pL drops of medium containing SARS-C0V-2 were added on top of the various materials and left at room temperature for either 5 minutes or 10 minutes. The absorption of the drops was evident immediately in the porous materials. Any remaining infectious virus was then retrieved from the treated surfaces using 50 pl of cell culture medium on top of the viral drops, which were transferred to target cells for infection. We measured infection in Vero cells at 48 hours, by scoring the percentage of spike-expressing cells.

[00256] To mimic the formation of surface fomites, virus containing droplets were placed on the surfaces and left settling for 5 or 10 min before the recovery and infection procedures. Figure 15 shows the effect of the settlement time and surface specification on resultant infection. In case of 5 min, the MFC thin film (spin-coating) of this work has led a threefold reduction in the number of infected cells when compared to the control infection group. The infection rate was further reduced down to low values comparable to the uninfected control group when the virus droplets were left on the MFC coated surface for 10 min prior to recovery. The results suggest that the porous MFC thin film has a clear inactivation effect towards the virus, within a short timeframe of a few minutes after the landing of the virus containing droplets. We interpret this quick and effective virus inactivation primarily as a consequence of the much- accelerated droplet evaporation, as shown in Figures 6-9. The droplet of 0.5 uL (the same volume as used in Figure 6 and 7) would have been dried out completely after 5 min, leaving the virus content exposed to the ambient environment and prone to disruption and inactivation. In contrast, no adverse effect on the virus viability was found on the glass and polyester surfaces, irrespective of the length of the settling time.

The glass and PET materials have been chosen as two representative non-porous surfaces that are commonly seen in everyday life. The results in Figure 15 imply that instead of modulating only the hydrophobicity or hydrophilicity of a surface, creating hydrophilic yet porous surfaces could be a more effective strategy against surface transmission of the virus.

[00257] In example 4.2, the MFC thin films’ ability to inhibit surface transmission of bacteria was tested. E. coli and S. epidermidis were incubated respectively in 10 ml L-B broth overnight in a 37 °C incubator with shaking at 150 rpm. Both species were pelleted and washed with 10 ml PBS solution twice and suspended in PBS to ODeoo 0.1 (E. coli-. 8.5 x 10⁷ cells/ ml, S. epidermidis-. 10.3 x 10⁷ cells/ ml). To the coated slides, 20 ul of the bacterial culture was added, slides were placed in 24 well plates which were sealed with parafilm and incubated at 3O°C for either 1 h or 24 h. After the set amount of time, surviving bacteria were recovered from the slides as follows, (i) Slides were placed into 0.7 ml PBS in 15 ml falcon tubes respectively and vortexed for 30 s. (ii)

Slides were further physically scraped with a spatula and the residue mixed into the respective 0.7 ml solution from (i). (iii) Samples were then sonicated for 3 x 1 min in a bath sonicator (GT Sonic, 40 Hz, 100 W). Serial dilutions were then performed and 10 ul of the final dilution was pipetted onto nutrient agar plates which were left to soak into the agar for 30 mins. Plates were then incubated at 37 °C overnight, after which colonies were counted to determine the antibacterial effect of the coatings.

[00258] Bacterial testing results using E.coli (Figure 16) and S. epidermidis (Figure 17) suggest that the MFC thin film is also able to suppress the proliferation of the two bacteria. Whilst the bare glass surface showed statistically no effect on the viability of both bacteria incubating on its top when compared to the control group, the viability of

E.coli was reduced by 43% and 54% when incubating on the MFC thin film for 1 and 24 h, respectively. S. epidermidis is especially vulnerable to the MFC coated substrates, with complete loss of viability after ih. The antibacterial effect of the MFC film can be again attributed to its hydrophilicity and porosity. It is known that hydrophilic surfaces can prevent the attachment of bacteria thus the formation of a biofilm due to the presence of a water molecule layer which hinders the adsorption of bacteria. The MFC thin film, in this scenario, enables the generation of a water barrier layer to bacteria adhesion, immediately and uniformly upon the deposition of the bacteria medium. [00259] In example 4.3, the MFC thin films’ ability to capture an individual SARS-CoV- 2 virus was studied. To replicate virus droplets as in a sneeze from an infected person, 0.5 pL drops of medium containing SARS-C0V-2 (England 2 stock 10⁶ lU-mlv¹) were added on top of the MFC thin film. Surface morphology of the thin films was examined by an atomic force microscope (AFM, Multimode, Bruker) with a tapping mode cantilever (NCHR-20, Apex Probes Ltd.). Figure 18 is an atomic force microscopy image of the MFC coating exposed to viral titre showing that the porous coating was able to capture individual virus.

Claims

1. An article comprising a surface and having on said surface a coating comprising at least about 8o wt% microfibrillated cellulose based on the total weight of the coating.

2. The article according to claim i, wherein the surface comprises a non- porous surface optionally selected from the group consisting of glass, ceramic, plastic, wood, metal and mixtures thereof.

3. The article according to claim 1 or claim 2, wherein the surface is a hard surface.

4. A method of applying a coating to a surface, the method comprising:

(ii) obtaining a surface coated with a coating comprising microfibrillated cellulose.

5. The method according to claim 4, wherein the composition is applied to the surface by spray-coating.

6. The method according to claim 4 or claim 5, wherein after the treatment of step (i), the composition is dried to form the coating by evaporation of the liquid component at room temperature.

7. The method according to any one of claims 4-6, wherein the surface to be treated comprises a non-porous surface optionally selected from the group consisting of glass, ceramic, plastic, wood, metal and mixtures thereof.

8. The method according to any one of claims 4-7, wherein the surface to be treated is a hard surface.

9. The method according to any one of claims 4-8, wherein the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 10 wt% based on the total weight of the composition, optionally wherein the composition comprises microfibrillated cellulose in an amount of about 0.1 to about 5 wt% based on the total weight of the composition.

10. The method according to any one of claims 4-9, wherein the composition comprises a water miscible component, optionally wherein the water miscible component is an alcohol.

11. The method according to any one of claims 4-10, wherein the composition comprises an inorganic particulate material.

12. The method according to any one of claims 4-11, wherein the composition comprises particles of silver, copper, copper oxide, bismuth, cobalt, platinum or a mixture thereof.

13. The method according to any one of claims 4-12, wherein the composition comprises a quaternary ammonium compound.

14. The article or method according to any preceding claim, wherein the coating has an inactivating effect on a microbe capable of causing an infection in a subject.

15. The article or method according to any preceding claim, wherein the coating has an inactivating effect on a virus capable of causing a viral infection in a subject, optionally wherein the virus is an RNA virus selected from the group consisting of a coronavirus (including a coronavirus selected from the group consisting of MERS-CoV, SARS-CoV, and SARS-C0V-2), an influenza virus, a rhinovirus, Measles virus and Mumps virus.

16. The article or method according to any preceding claim, wherein the coating is obtained in the form of a film.

17. The article or method according to any preceding claim, wherein the coating has a thickness of between about 50 and about 2000 nm.

18. The article or method according to any preceding claim, wherein the coating is invisible.

19. The article or method according to any preceding claim, wherein the coating has a porosity of between about 20-70%.

20. The article or method according to any preceding claim, wherein the water contact angle (°) of the coating is at least about 50% lower than the water contact angle of a corresponding untreated surface.

21. The article or method according to any preceding claim, wherein the microfibrillated cellulose has a fibre steepness of from about 20 to about 50.

22. The article or method according to any preceding claim, wherein the microfibrillated cellulose has a d_5O ranging from about 5 pm to about 500

23. An article comprising a surface coated with a coating applied according to the method of any one of claims 4-22.

24. Use of a composition comprising a suspension of microfibrillated cellulose in a liquid component comprising water, and optionally a water miscible component, in a method of preparing an antimicrobial surface coating.

25. Use of microfibrillated cellulose for inactivating a microbe capable of causing an infection in a subject.

26. A method of inactivating a microbe capable of causing an infection in a subject, comprising using microfibrillated cellulose.

27. The use or method according to claim 25 or claim 26, wherein the microfibrillated cellulose is in the form of a surface coating.

28. The use or method according to claim 27, wherein the surface coating is invisible.