WO2023227599A1

WO2023227599A1 - Antimicrobial coating composition

Info

Publication number: WO2023227599A1
Application number: PCT/EP2023/063784
Authority: WO
Inventors: Connell BOAL; James Joseph Brennan; Thomas Patrick Patton; John Reginald Barrett
Original assignee: Atlantic Technological University
Priority date: 2022-05-23
Filing date: 2023-05-23
Publication date: 2023-11-30

Abstract

Antimicrobial coating compositions that can maintain a sterile surface and prevent pathogenic microbial adhesion comprising a storage-stable antimicrobial A3IS system and silicone.

Description

“Antimicrobial Coating Composition”

Field of the Invention

This invention relates to antimicrobial coating compositions, in particular compositions that can maintain a sterile surface and prevent pathogenic microbial adhesion.

Background to the Invention

In the US alone it is estimated that 50-70% of the 2 million healthcare associated infections can be attributed to indwelling medical devices such as urinary catheters or prosthesis (VanEpps & Younger, 2016).

It is known to provide an antimicrobial coating on a medical device to prevent bacterial proliferation around or on the device. This reduces the incidences of hospital acquired infections, reduces the need for antibiotic prescription, avoids longer hospital stays for patients and reduces the hours required by hospital staff when addressing any infections that occur from indwelling medical devices.

Examples of different varieties of non-drug eluting antimicrobial device coatings are outlined in the table below.

Many metallic and copolymer coatings are relatively expensive. Also, metallic based coatings can be toxic. Heavy metal exposure can actually induce antimicrobial resistance on its own. That is why metallic coatings are seen as a short-term solution as prolonged exposure to some metallic based coatings can induce AMR (antimicrobial resistance). Metallic coatings can be very hazardous also if the patient is over exposed.

Biofilms occur on medical devices when planktonic bacteria migrate on to a surface of the device and proliferate. Bacterial biofilms can be single type or have multiple different types of colonies present. The adherent cells produce a slimy extracellular matrix that is composed of extracellular polymeric substances. Biofilms are especially dangerous as standard antibiotic treatments are often ineffective as they cannot penetrate the outer wall of the biofilm.

Medical device manufacturers have also tried coating medical components in various antibiotics in order to prevent infection, however this has led to a dramatic increase in rates of antibiotic resistance seen in recent years.

The present invention is directed towards addressing this problem, and in particular to providing new antimicrobial coating compositions that can maintain a sterile surface and prevent pathogenic microbial adhesion.

US 2017\0072024A1 discloses a topical antimicrobial composition for the treatm4ent of infections of the skin and mucous membranes, the composition comprising a mixture of at least one carbohydrate, glucose oxidase and zinc oxide. RU 2644745C1 discloses a wax protective agent for the skin of the hands which includes bee honey. WO 2019\197839A1 discloses tissue scaffold matrices which may be used for coating medical devices. WO 2009\064879A2 discloses antimicrobial coatings for medical devices.

Summary of the Invention

According to the invention there is provided an antibacterial coating composition comprising A3IS and silicone.

A3IS is a storage stable antibacterial, antifungal, antiviral and immunostimulatory system. A3IS is described in WO 2008/041218, the content of which is included herein by reference, and comprises a storage-stable antimicrobial system comprising an oxidoreductase enzyme, a substrate for the oxidoreductase enzyme and hydrogen peroxide in an aqueous solution wherein the substrate for the oxidoreductase enzyme is present up to 90% by weight and water is present up to 20% by weight based on the weight of the total system; the system has a pH from approximately 4 to 8; and the system provides a two-stage hydrogen peroxide release. Various examples of A3IS are described in WO 2008/041218. The A3IS used in this invention does not include natural honey which would not be suitable.

Upon hydration, A3IS produces a sustained release of hydrogen peroxide which is a well known biocide. The sustained delivery of hydrogen peroxide will maintain a sterile surface and prevent bacterial attachment to the device. Hydrogen peroxide has been shown to induce angiogenesis, collagen deposition and cause stem cells to proliferate. Hydrogen peroxide is a broad spectrum antimicrobial compound which demonstrates efficacy against bacteria, fungi and viruses.

Silicone has a low chemical reactivity, low toxicity and good biocompatibility. The silicone provides a coating which prevents unwanted abrasion between the device implant and the surrounding tissue. Silicone is inherently hydrophobic, so it actively repels water and as such can repel bacterial attachment. The antibacterial coating composition can be applied to disposable medical devices such as scalpels, sutures and staples as well as implantable devices such as hip or knee prosthesis to prevent bacterial adhesion and thus reduce the risk of infection and therefore reduce the necessity for antibiotics.

Due to the ever-increasing rates of antimicrobial resistance, viable solutions to reduce the over reliance on antibiotics are needed as soon as possible. By using the antibacterial coating of the invention on medical devices, it will reduce the incidences of healthcare acquired infections and rejections of medical components thus reducing the volume of antibiotic prescriptions.

While the invention provides an antimicrobial coating for medical devices, the antibacterial coating composition could also be used in several other areas including, but not limited to, hospital ventilation systems, coatings for digital screens, door handles and filtration membranes for rooms that must minimize pathogenic microbes.

In one embodiment of the invention the composition comprises A3IS and silicone in a ratio of between 1 :1 and 10:1 by weight.

In another embodiment the composition comprises equal parts by weight of A3IS and silicone.

In another embodiment the A3IS comprises by weight:

Glucose in the range of 35% - 40%

Fructose in the range of 38% - 41 %

Maltose in the range of 10% - 17%

Sucrose in the range of 1.5% - 2.5%

Glucose oxidase in the range of 0.5% - 12.5%

Water in the range of 0% - 15%.

In another embodiment the A3IS comprises by weight:

35% Glucose

38% Fructose

10% Maltose

1.5% Sucrose 0.5% Glucose oxidase

15% Water.

In another embodiment the A3IS comprises by weight:

35% Glucose

38% Fructose

12% Maltose

2.5% Sucrose

12.5% Glucose oxidase.

In another embodiment the A3IS comprises by weight:

40% Glucose

41 % Fructose

17% Maltose

1.5% Sucrose

0.5% Glucose oxidase.

In another embodiment, the A3IS comprises by weight:

40% Glucose

40% Fructose

10% Maltose

10% Glucose Oxidase.

In another embodiment, the A3IS comprises by weight 90% Glucose and 10% Glucose Oxidase.

In another embodiment, the A3IS comprises by weight 40% Fructose, 0.1-10% Glucose Oxidase and 50-59.9% water.

In another embodiment, the antimicrobial coating composition further includes a surfactant.

In another embodiment, the surfactant comprises poloxamer or lecithin.

In another embodiment, the surfactant comprises poloxamer and lecithin. In another embodiment, the A3IS comprises by weight:

Glucose in the range 35% - 40%

Fructose in the range of 38% - 41%

Maltose in the range of 10% - 17%

Sucrose in the range of 1 .5% - 2.5%

Glucose oxidase in the range of 0.5% - 12.5% Polar solvent in the range of 0% - 15%.

In another embodiment, the polar solvent is selected from polypropylene glycol, ethanol, isopropyl alcohol and acetic acid.

In another aspect a method for manufacturing the antibacterial coating composition includes the steps of mixing and dissolving the sugars at a temperature in the range 80-100°C, and subsequently, as the mixture is cooling, adding the glucose oxidase.

In another aspect a coating method comprises the steps of mixing and dissolving the sugars at a temperature in the range of 80-100°C, while the sugar mixture is still warm, dipping the object into the mixture and removing the object from the mixture for coating an exterior of the object with a layer of the sugar mixture, and then dipping the object into glucose oxidase.

In another embodiment, the object is sequentially dipped into the warm sugar mixture and then into the glucose oxidase a number of times to create a multilayered coating of the composition on the object.

Brief Description of the Drawings

The invention will be more clearly understood by the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a contact angle analysis graph;

Fig. 2 is a table indicating a number of antibacterial coating compositions of the invention; Fig. 3 is a graph illustrating the activity of the various antimicrobial coating compositions of the invention; and

Fig. 4 is a graph providing a minimum inhibitory concentration comparison between medical device grade honey products and the antimicrobial composition of the invention.

Detailed Description of the Preferred Embodiments

To prepare an antimicrobial coating composition of the invention A3IS was mixed with various grades of silicone and tested as an antimicrobial coating for surgical sutures and urinary catheters. Surprisingly, the activity of the newly mixed product was tested and showed the same level of antimicrobial activity after mixing as the standard neat A3IS product. The antimicrobial coating composition can be sprayed on any medical device and depending on the surface charge of the device, can be altered to ensure a uniform coating depth around the part. The low friction of silicone makes it ideal for both external and internal medical device implants.

Examples of antimicrobial coating compositions according to the invention are discussed below.

The table below describes the different batches that were prepared.

Table 1 : Summary of batches used.

Powder, Neat & Silicone Solution Manufacture • Powder batch 1 & 2 were mixed as per the ratios seen in T able 1 above. 100g total batch size was made for each powder sample in a sealable container, while the gel batch was made using one 25g tube of product mixed with 25g of silicone lubricant.

• Continuously invert the mixture for 2 minutes until yellow colour has dispersed throughout container. Ensure no clumps of sugar are present after mixing.

• Spray 48ml of the silicone lubricant into a clean container.

• Weigh 50g of the powder batch and place into same container as the container.

• Use 3-5 extra sprays of the silicone to wash down the container containing the A3IS powder to make up a 100ml solution.

• Mix the solution using a spatula for 60 seconds or until uniformly dispersed.

Activity Testing

• Measure 95ml of deionised water into a clean container

• Weigh 1 g of the powder/silicone solution and transfer to container containing deionised water.

• Use 4ml of deionised water in a syringe to wash down the sides of the powder/silicone container so all is transferred to the container with deionised water.

• Use the MQuant Hydrogen Peroxide measuring sticks to dip the solution and record the reading of hydrogen peroxide.

Suture Coating

• Soak the non-absorbable suture in the powder/silicone solution

• Press down the suture into the solution and close the container cap so that the solution can be inverted and mixed.

• Allow the suture to soak for a minimum of 10 minutes.

• Allow the sutures to dry.

• If required, a uniform thickness of the antimicrobial coating composition along the length of the suture can be achieved using a die.

Table 2: Release activity test with various presentations of A3IS and silicone. As can be seen all values recorded were identical.

The antimicrobial coating composition can be coated by various methods depending on the application. Initial trials have focused on simple dip coating and soaking processes which are effective depending on the application. Grafting process have been trialled which proved effective for larger components.

Electrospraying was found to be very useful for creating very thin layers of the antimicrobial coating on smaller surfaces. The versatility of the antimicrobial coating composition means it can quite simply be painted on to any surface or device to achieve an antimicrobial coating.

Silicone adheres quite readily to itself so a multilayer approach can be taken determined by the length of time the coating needs to remain active for.

The function of the invention is the prevention of infection by using an antimicrobial barrier or coating to prevent microbial proliferation by blocking adhesion to the component or surface. The aim of the coating is to reduce to overreliance and prescriptions of antibiotics and thus offer a viable solution to the increasing rates of antimicrobial resistance (AMR) seen each year. Hydrogen peroxide is a well-known biocide and is effective at combating bacteria, fungi and even viruses with ease. Hydrogen peroxide also effectively destroys any type of biofilm and by using a sustained release of hydrogen peroxide like that offered with A3IS in the antimicrobial coating composition it results in the complete removal of any biofilms present. The antimicrobial coating composition of the invention offers a non-antibiotic approach to reducing the number of hospital associated infections seen each year globally.

Various silicone products can be used. NuSil® (Avantor, Radnor, PA19087, USA) provide various grades and presentations of medical grade silicone. Silicone can be provided in many different forms and depending on the intended use of the antimicrobial coating, different presentations of silicone will be used. Examples of the types of silicone to be used and their desired ratios are given in the table below. All silicones used for medical grade applications will require medical device grades of silicone but for other applications such as antimicrobial coatings for door handles and other common equipment, other versions of silicone are available.

The list in the table above is not exhaustive but gives an indication of the range of ratios and types of silicones which can be used in different applications. In many instances parts will be coated using a multi-layer approach whereby an even ratio mix of silicone and antimicrobial may be used for the first layer with a reduction ratio of antimicrobial to silicone for outer layers. For example, in situations where reducing friction is a key parameter, such as in the case of a short term medical implant such as surgical sutures, a low viscosity silicone oil and antimicrobial solution would be used. In this instance the silicone would have a high ratio to antimicrobial solution to reduce friction and reduce the insertion force required for the suture through skin to prevent unwanted adverse effects from the suture. As the implant is only for short term use it does not require an excessive amount of antimicrobial in order to maintain a sterile site while the device is in use. For long term medical implant devices, such as hip and knee prosthetics, a more uniform ratio of A3IS to silicone would be used where preventing friction is not a core requirement. In instances where longer term implants are used, a multi-layer approach would be most suitable in order to provide prolonged antimicrobial activity around the insertion site and prevent surgical implant infection and thus reduce the incidences of repeat surgery or further hospital stays.

Further A3IS compositions that can be used in combination with silicone are indicated in the table below.

Advantages of the Invention

• A3IS has good biocompatibility characteristics o Concentrations x20 stronger than those used in a clinical dose were shown to have no toxic or irritant effects during a human trial. • The A3IS & Silicone coating mixture offers long term antimicrobial release which will reduce the incidences of microbial adhesion and thus prevent device failure or infection. o The therapeutic release of hydrogen peroxide at low doses has a secondary effect in inducing the host's immune system. Surprisingly there is no drop off in activity when A3IS is mixed with silicone (Table

2)

• The limiting factor of the A3IS antimicrobial product is the availability of glucose. Once the glucose has been depleted the product ceases production of hydrogen peroxide. o A surprising benefit of using A3IS in the antimicrobial coating composition is that it has access to available glucose within the human body and as such can offer prolonged hydrogen peroxide release. • A3IS is cheaper than the majority of metallic and copolymer coatings.

• A3IS is much less toxic than metallic based coatings or devices. o Heavy metal exposure can actually induce antimicrobial resistance on its own that’s why metallic coatings is seen as a short-term solution as prolonged exposure to some metallic based coatings can induce AMR. Metallic coatings can be very hazardous also if the patients is over exposed.

• Due to the generation of reactive oxygen species, there is a much less likely chance for resistance to develop. o Reactive oxygen species (ROS) target all aspects of microbes. They can puncture cell walls and actively destroy the core components of a pathogenic microbe. While antibiotics only target a specific marker on a cell, ROS is broad spectrum in it’s antimicrobial potential and as such can combat bacteria, fungi or even viruses making it much better at combating infectious diseases than a standalone antibiotic.

• Sustained low dose delivery of reactive oxygen species (hydrogen peroxide) results in a less toxic response than using a neat solution of ROS. o Sustained low dose delivery of ROS from A3IS results in the complete and irreversible kill of all pathogens it comes in contact with. The lower dose results in a much less toxic response from the host and as such offers better biocompatibility.

• Reactive oxygen species (ROS) has very well-known anti-biofilm properties. o While antibiotic coatings can be used for combating some types of infection, the biofilms that can develop from some infections are the core reason why some antibiotics become completely ineffective. ROS can effectively destroy biofilms and dissipate the matrix formed which reduces the viability of the microbial colony substantially. o Biofilm formation is often cited as the primary reason for medical device failure. The introduction of any medical device, no matter their biocompatibility, increases the potential surface area for pathogenic microbes to adhere to and thus puts the patient at a higher potential risk of infection.

The A3IS & Silicone mix can be tailored based on the desired application. o For example, a higher ratio of silicone to A3IS would be used for an application such as surgical suture coating as reducing friction is of upmost importance during insertion of the suture in surgery. For applications such as long-term implants i.e. heart values or prosthetics a higher ratio of A3IS would be used as long term antimicrobial activity is the most important aspect for these applications.

The composition of the invention would be commercially viable as antimicrobial lubricants also. In the case of urinary catheters for example silicone is often used as a lubricant for insertion of catheters. When this occurs due to the hydrophobic nature of silicone, it can actively push pathogenic microbes around the urethra into the bladder. If the composition of the invention was used it would actively eliminate pathogenic bacteria of fungi in the surrounding area during insert and thus could prevent infection.

The coating composition of the invention can be used in contaminated locations or those with a high prevalence of pathogenic microbes as it will dissolve quickly into the surrounding tissues and could be used to complement existing antimicrobial coatings.

To prepare the composition of the invention, the sugars are mixed and dissolved first at a higher temperature (80-100C) and then subsequently as the mixture is cooling the glucose oxidase is added as a final step. The coatings can be prepared in a multilayer process i.e. while the sugar mixture is still viscous and warm the polymer or metal samples are dipped into the mixture and very slowly removed to leave a thin “base" layer on the component, after this the components can be dipped into glucose oxidase and this process repeated several times over to create a multi-layer.

The use of surfactants in the composition will improve the mixability of the components and prevent them separating during storage. Contact angle is a method of measuring how well a coating can adhere to a substrate and as is shown in Fig. 1 mixing A3IS with various levels of surfactants produces a smaller contact angle i.e. better adhesion to the polymer bases.

As many polymers are hydrophobic by nature and the A3IS mixture contains approximately 15% water, the coating will be naturally repelled by the polymer. Further modified versions of A3IS were created (see Fig. 2) which replaced water with different polar solvents such as ethanol, IPA, polyethylene glycol and acetic acid which had low melting points but would not necessarily dissolve at normal body temperature to increase the stability and shelf life of the coating itself. Each of the modified versions of A3IS produced without water had the same antimicrobial activity and hydrogen peroxide release activity when tested (see Fig. 3).

When using the modified versions of A3IS which can be manufactured under select conditions which contain no water, you ensure that hydrogen peroxide production only occurs once hydrated or when inserted into the patient. By doing this you can ensure definite levels of antimicrobial activity each time when used and also results in a much longer shelf life.

When comparing A3IS to natural or even medical device grade honey, the antimicrobial activity is substantially greater with A3IS. Fig. 4 shows the minimum amount to product required to prevent some of the most common pathogenic bacteria from proliferating. As you can see A3IS is significantly more effective than Medihoney and Surgihoney at combatting bacteria.

In this specification the terms “comprise, comprises, comprised and comprising” or any variation thereof and the terms “include, includes, included and including” or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail within the scope of the appended claims.

Claims

1. An antibacterial coating composition comprising A3IS and silicone.

2. The antibacterial coating composition as claimed in claim 1 , wherein the composition comprises A3IS and silicone in a ratio of between 1 :1 and 10:1 by weight.

3. The antibacterial coating composition as claimed in claim 1 or claim 2, wherein the composition comprises equal parts by weight of A3IS and silicone.

4. The antibacterial coating composition as claimed in any preceding claim, wherein the antimicrobial coating composition further includes a surfactant.

5. The antibacterial coating composition as claimed in claim 4, wherein the surfactant comprises poloxamer or lecithin.

6. The antibacterial coating composition as claimed in claim 4, wherein the surfactant comprises poloxamer and lecithin.

7. The antibacterial coating composition as claimed in any one of the preceding claims, wherein the A3IS comprises by weight: Glucose in the range of 35% - 40%

Fructose in the range of 38% - 41% Maltose in the range of 10% - 17% Sucrose in the range of 1 .5% - 2.5% Glucose oxidase in the range of 0.5% - 12.5% Water in the range of 0% - 15%.

8. The antibacterial coating composition as claimed in claim 7, wherein the A3IS comprises by weight:

35% Glucose 38% Fructose 10% Maltose

1.5% Sucrose

0.5% Glucose oxidase

15% Water.

9. The antibacterial coating composition as claimed in claim 7, wherein the

A3IS comprises by weight:

35% Glucose

38% Fructose

12% Maltose

2.5% Sucrose

12.5% Glucose oxidase.

10. The antibacterial coating composition as claimed in claim 7, wherein the

A3IS comprises by weight:

40% Glucose

41 % Fructose

17% Maltose

1.5% Sucrose

0.5% Glucose oxidase.

11. The antibacterial coating composition as claimed in claim 1 , wherein the

A3IS comprises by weight:

40% Glucose

40% Fructose

10% Maltose

10% Glucose Oxidase.

12. The antibacterial coating composition as claimed in any one of claims 1 to 6, wherein the A3IS comprises by weight:

Glucose in the range 35% - 40%

Fructose in the range of 38% - 41%

Maltose in the range of 10% - 17%

Sucrose in the range of 1 .5% - 2.5%

Glucose oxidase in the range of 0.5% - 12.5%

Polar solvent in the range of 0% - 15%.

13. The antibacterial composition as claimed in claim 12, wherein the polar solvent is selected from polypropylene glycol, ethanol, isopropyl alcohol and acetic acid.

14. The antibacterial coating composition as claimed in claim 1 , wherein the A3IS comprises by weight 90% Glucose and 10% Glucose Oxidase.

15. The antimicrobial coating composition as claimed in claim 1 , wherein the A3IS comprises by weight 40% Fructose, 0.1-10% Glucose Oxidase and 50- 59.9% water.

16. A method for manufacturing the antibacterial coating composition as claimed in any preceding claim, including the steps of mixing and dissolving the sugars at a temperature in the range 80-100°C, and subsequently, as the mixture is cooling, adding the glucose oxidase.

17. A method for coating an object with the antibacterial composition as claimed in any one of claims 1 to 15, comprising the steps of mixing and dissolving the sugars at a temperature in the range of 80-100°C, while the sugar mixture is still warm, dipping the object into the mixture and removing the object from the mixture for coating an exterior of the object with a layer of the sugar mixture, and then dipping the object into glucose oxidase.

18. The method as claimed in claim 17, wherein the object is sequentially dipped into the warm sugar mixture and then into the glucose oxidase a number of times to create a multi-layered coating of the composition on the object.