Antimicrobial compositions and articles

Abstract

An article formed of a composition, wherein the composition comprises: a hydrogen sulfide releasing agent, a graphene-based material, and polymer, and wherein the hydrogen sulfide releasing agent and the graphene-based material are encapsulated within the polymer.

Description

[0001] ANTIMICROBIAL COMPOSITIONS AND ARTICLES

[0002] Field of the Invention

[0003] The present invention relates to a composition that can store relatively high concentrations of a hydrogen sulfide releasing agent, and release hydrogen sulfide at a controlled rate. Articles comprising the composition have applications as medical devices (e.g. wound dressings, catheters, and heart valves). Compositions comprising the composition have applications including as antimicrobial agents and for the treatment of wounds.

[0004] Background of the Invention

[0005] Over the past decade, antibacterial gas therapy, focusing on gases like nitric oxide, hydrogen sulfide (H2S) and carbon monoxide, has gained significant attention. These gases are endogenously produced in mammals and bacteria and have been shown to act as crucial signalling molecules that protect against oxidative stress. In vivo, H2S is typically released in low pH or under hypoxic conditions, which are characteristic of diseased cells.

[0006] H2S is a gas that has therapeutic applications due to, for example, its antimicrobial effects. H2S-releasing agents exhibit excellent therapeutic effects towards hard-to-heal infected wounds, thereby enhancing wound healing. Since H2S is a small, gaseous molecule it can diffuse through the porous surface of a biofilm.

[0007] H2S contributes to VEGF-stimulated angiogenesis and blood vessel formation by exerting its effect on endothelial cells through KATP, ATP- sensitive potassium channels. Hence, the controlled and sustained release of H2S has been found to accelerate the healing process in wounds.

[0008] The therapeutic use of H2S requires it to be provided at a suitable concentration. Local concentrations of lOOpM and above are known to be effective. However, concentrations of H2S above lOOmM are toxic. The local concentration of H2S should therefore be controlled to be from 100 pM to 100 mM. H2S releasing agents such as sodium sulfide (Na2S) and diallyl trisulfide (DATS) are molecules that release H2S in response to specific triggers, providing an exogenous source of H2S. These H2S releasing agents are typically used to produce H2S systemically and are not targeted to specific cellular sites of action.

[0009] H2S sources such as Na2S and DATS typically release H2S at a high rate, providing a short-lived bolus dose, which may lead to toxic concentrations of H2S developing.

[0010] Further, H2S released into the body tends to have a half-life of around 2-5 seconds before oxidation, so bolus doses do not provide long-lasting effects, and the commercial utility of such FUS-releasing materials for in vivo applications is limited.

[0011] The clinical and pre-clinical research on FUS-based treatments is primarily dedicated to the development of FUS-releasing releasing agents. Polymeric nanoparticles, micelles, hydrogels, and films have been investigated for releasing H2S.

[0012] For example, a H2S delivery system has been developed using polymersomes, made of polycaprolactone (PCL) and a S-aroylthiooxime (SATO), a H2S releasing agent, which were applied in a spray format to treat bacterial infections in wounds. In the presence of cysteine, these polymersomes gradually released H2S for up to 12 hours (Rong et al., 2023, Bioactive Materials, 19, pp. 198-216).

[0013] Zinc sulfide has been incorporated, as a FUS releasing agent, within nanoparticles. Such nanoparticles function as pH-triggered H2S generators, specifically targeting the biofilm microenvironment. This releasing mechanism was shown to depolarize bacterial cell membranes, disrupting the integrity of MRSA, and enhanced re-epithelialisation.

[0014] However, the release profiles of conventional hydrogen sulfide releasing products do not meet clinical endpoints.

[0015] H2S delivery via small molecule releasing agents is often limited by rapid release, low water solubility, lack of target specificity, and / or toxicity.

[0016] The present invention has been devised with the foregoing in mind. Summary of the Invention

[0017] According to a first aspect the claimed invention provides an article formed of a composition, wherein the composition comprises: a hydrogen sulfide (H2S) releasing agent, a graphene-based material, and polymer, and wherein the H2S releasing agent and the graphene-based material are encapsulated within the polymer. Examples of suitable H2S releasing agents include Na2S and DATS.

[0018] Surprisingly, it has been found that compositions comprising a H2S releasing agent, a graphene-based material and polymer exhibit significant antibacterial activity against Gram-positive bacteria and / or against Gram-negative bacteria in comparison to either graphene-based material, Na2S, DATS, or the polymer alone. The graphene-based material is preferably graphene oxide, but could be graphene (e.g. porous graphene) and / or reduced graphene oxide.

[0019] It has been found that the graphene-based material and the polymer can successfully be combined with the H2S releasing agent to provide a safe and effective dose of H2S that is sustained over a therapeutically useful time period.

[0020] Preferably the article is a medical device, such as a wound dressing (e.g. a bandage and / or gauze), a catheter, and / or an implant (such as a heart valve).

[0021] The H2S is released from the H2S releasing agent when the composition is contacted with moisture, which is an ideal release stimulus for in vivo applications such as wound healing. Depending on the H2S releasing agent and / or polymer chosen, release of H2S may be triggered by other factors such as exposure to enzymes and / or a change in pH.

[0022] When in contact with moisture, the composite can release H2S at a clinically appropriate rate of 300 pM per mg per hour.

[0023] Preferably the article comprises one or more surface (e.g. sheath) layer(s) of polymer and one or more core layer(s) of the composition. Such a layered structure can assist with controlling the release of H2S, for example upon exposure to moisture. It has been found that the polymer provides structural integrity, as well as allowing the H2S to diffuse from within its structure.

[0024] Preferably the polymer is biodegradable, for example a polyester, such as polycaprolactone (PCL), poly-3 -hydroybutyrate and / or polylactic acid, and / or a cellulose based polymer such as cellulose acetate and / or celluloid. Biodegradable polymers provide the benefit of further exposing the structure to the biological cues in a time-controlled manner, releasing H2S first from the outermost section and then from inner sections. Polymers such as PCL additionally provide the benefit of being biologically compatible.

[0025] The composition may be present as fibres. Providing the composition as fibres is understood to enhance the control of the rate of release of the hydrogen sulfide.

[0026] Sustained antimicrobial delivery system in wound dressing applications hence, a promising alternative to traditional antibiotics.

[0027] Crucially, the present invention enables both the rate of release of H2S and the location of release to be controlled. Therefore, H2S can be provided to a site of need in a safe and therapeutically effective concentration.

[0028] Graphene-based materials, such as graphene oxide, are useful for their high surface area and ability to adsorb H2S, allowing a high amount of H2S to be stored in a given volume. There is evidence that compositions containing graphene-based materials, such as graphene oxide, have a higher loading capacity than compositions that do not contain graphene-based materials. This allows the compositions of the invention to safely and successfully contain higher amounts of the H2S releasing agents, and to thereby improve antibacterial efficacy. Therefore, the graphene-based material allows the release of H2S to be sustained at a therapeutically appropriate rate and for a therapeutically appropriate period of time.

[0029] It has also been found that not using graphene-based material prevents a high amount of H2S from being stored in the composite. This limitation is addressed by the unique properties of graphene-based materials, such as graphene oxide, that have a high surface area and include functional groups (e.g., hydroxyl, carboxyl, and epoxy groups) that facilitate stronger interactions and higher loading capacities of H2S-releasing agents such as DATS and Na2S. This superior loading efficiency is further supported by Raman and FTIR data, which confirm the successful integration of these agents into the graphene-based composite.

[0030] The polymer provides the slow release characteristics that are essential for controlling the rate of release of the H2S. It has been found that not using the polymer and / or the graphene-based material would provide rapid and uncontrolled release (i.e. burst release) of H2S, leading to high concentrations of H2S and toxicity.

[0031] Overall, the present invention provides a multifunctional platform for wound healing applications.

[0032] According to a second aspect the claimed invention provides a composition comprising: a H2S releasing agent, graphene-based material, and polymer, and wherein the H2S releasing agent and the graphene-based material are encapsulated within the polymer. It will be appreciated that the article of the first aspect may comprise the composition of the second aspect.

[0033] The composition may be administered to a patient to treat, ameliorate and / or prevent a TUS-responsive disease or condition. FUS-responsive diseases and conditions include those selected from the list consisting of a microbial (e.g. bacterial) infection (e.g. the treatment of a wound), myocardial infarction, hypertension, peripheral arterial disease, cardiovascular diseases, atherosclerosis, ischemia reperfusion, heart failure, peptic ulcer disease, acute and / or chronic inflammatory diseases (e.g. an autoimmune disease, arthritis, lupus, fibromyalgia, and chronic fatigue syndrome), diabetes, diabetic kidney disease, gastric ulcers, metabolic syndrome, stroke, inflammatory bowel disease, cancer, neurological disorders / diseases, ethylmalonic encephalopathy, Parkinson’s disease, Alzheimer’s disease, and erectile dysfunction.

[0034] As such, according to a third aspect the claimed invention provides the composition of the second aspect for use as a medicament. According to a fourth aspect the claimed invention provides the composition of the second aspect for use in the prevention, amelioration and / or treatment of a FUS-responsive disease or condition. According to a fifth aspect the claimed invention provides a pharmaceutical composition comprising the composition of the second aspect and a pharmaceutically acceptable carrier and / or diluent. According to a sixth aspect the claimed invention provides the use of the composition of the second aspect for the manufacture of a medicament, for example wherein the medicament is for the prevention, amelioration and / or treatment of a Irresponsive disease or condition. According to a seventh aspect the claimed invention provides a method of prevention, amelioration and / or treatment of a subject, comprising administering a composition of the second aspect; for example, wherein the method is a method of prevention, amelioration and / or treatment of a hydrogen sulfide-responsive disease or condition.

[0035] Preferably the composition is for the treatment of a disease or condition that is a bacterial infection or a cardiovascular disease.

[0036] According to an eighth aspect the claimed invention provides a method of preparation of a fibre composite, wherein the method comprises: providing a liquid mixture (e.g. solution and / or suspension), wherein the liquid mixture comprises a polymer, graphene-based material loaded with a hydrogen sulfide releasing agent, and a solvent; spinning the liquid mixture in a vessel (i.e. rotating the vessel about a central axis while the liquid mixture is in the vessel, centrifugal spinning), wherein the vessel comprises an orifice on the radially outermost wall, such that the liquid mixture escapes from the vessel through the orifice so as to form the fibre composite. The method of the eighth aspect may be used to prepare a composite of the second aspect and / or an article of the first aspect.

[0037] According to a ninth aspect the claimed invention provides a method of preventing, treating or ameliorating a microbial infection in a tissue of a subject, the method comprising contacting an article of the first aspect and / or a composite of the second aspect with the tissue. The tissue may be broken, wounded and / or injured. The tissue may be infected. The tissue may be skin, for example infected, broken, wounded and / or injured skin. The step of contacting the article and / or the composite with the tissue is performed by contacting the article and / or the composite with the tissue for a period of time of 1 minute or longer. The period of time may be 10 minutes or longer, such as 1 hour or longer, or 4 hours or longer. The period of time may from 1 minute to 48 hours, or from 1 minute to 24 hours, such as from 1 hour to 24 hours. According to a tenth aspect the claimed invention provides a method of achieving sustained release of hydrogen sulfide, the method comprising: providing an article of the first aspect and / or a composition of the second aspect; and exposing the article and / or the composition to moisture. The method of the tenth aspect may achieve a desired concentration of hydrogen sulfide in an environment surrounding the article and / or composition, such as a concentration of from 100 pM to 100 mM (preferably from 100 pM to lOmM, more preferably about 300 pM).

[0038] According to an eleventh aspect the claimed invention provides the use of an article of the first aspect and / or a composition of the second aspect as an antibacterial agent, for example against Gram positive bacteria and / or Gram negative bacteria. The use of the eleventh aspect may not be a method of treatment of the human or animal body by therapy. The use may comprise the step of exposing at least a portion of a surface of an article to the article and / or the composition.

[0039] Detailed Description of the Invention

[0040] The present invention generally relates to a composition comprising: a hydrogen sulfide releasing agent, graphene-based material, and polymer, and wherein the hydrogen sulfide releasing agent and the graphene-based material are encapsulated within the polymer. This composition is defined by the second aspect. The present invention finds application in the controlled release of hydrogen sulfide, which is useful in a variety of therapeutic applications.

[0041] Preferably the composition is present as fibres. Providing the composition as fibres is understood to control the rate of release of the hydrogen sulfide. The fibres may have a number average (mean) diameter of 50pm or less, such as 20 pm or less, or 15 pm or less, such as 12 pm or less, or 10 pm or less, or 5 pm or less. The number average (mean) diameter may be 0.01 pm or more, such as 0.1 pm or more, or 0.5 pm or more, such as 1 pm or more. The fibres may have a number average (mean) diameter of from 0.01 to 50 pm, such as from 0.1 to 15 pm. The number average (mean) diameter may be determined by analysis of micrographs (e.g. scanning electron micrographs) using Image J software. Preferably the hydrogen sulfide releasing agent is loaded (sorbed) onto the graphenebased material, such that the composite comprises graphene-based material loaded with the hydrogen sulfide releasing agent.

[0042] Article

[0043] The first aspect provides an article formed of a composition, wherein the composition comprises: a hydrogen sulfide releasing agent, graphene-based material, and polymer, and wherein the hydrogen sulfide releasing agent and the graphene-based material are encapsulated within the polymer.

[0044] Preferably the article comprises two or more layers, wherein the composition is present in one or more (e.g. not all) of the layers. The composite may be contained in the core of a two or more layered article (e.g. where the article comprises a core and a sheath). Preferably the article comprises a first layer comprising the polymer without the hydrogen sulfide releasing agent and / or the graphene-based material, and a second layer comprising the composition. Preferably the article comprises three or more layers, wherein the external / outermost layers do not comprise the composition. Preferably the article comprises two or more layers, wherein the external / outermost layers comprise 50% or less, such as 20% or less, or 10% or less, such as 1% or less of the composition by weight. The composite may be contained in the central layer of a three or morelayered article.

[0045] H2S is known to be a vasodilator, relaxing blood vessels, protecting against myocardial ischemia, and to have cytoprotective effects, protecting against oxidative stress. H2S has anti -microbial, anti-inflammatory, and pro-angiogenic effects.

[0046] The various biological effects of H2S allows the article to have particular applications in the field of medical devices. The article may provide benefits in terms of wound healing, for example increasing the rate of wound healing and / or reducing complications associated with wound healing.

[0047] Preferably the article is a medical device, such as a dressing (e.g. a bandage, plaster and / or gauze), a catheter, and / or an implant (such as a heart valve). The dressing (e.g. a wound dressing), for example a hydrocolloid dressing, a hydrogel dressing, a foam dressing, a hydrofiber (sodium carboxymethylcellulose fiber) dressing, an alginate dressing, a collagen dressing, a foam dressing, a bandage, a transparent dressing, a cloth dressing, gauze (e.g. paraffin gauze), a low adherent dressing, or a semi-permeable film (e.g. polyurethane coated with acrylic) dressing.

[0048] The article (e.g. as a dressing) may comprise cotton (e.g. woven cotton), wool, cellulose, plastics such as polyethylene (PE), polyvinyl chloride (PVC), carboxymethyl-cellulose, polyurethane and / or alginate.

[0049] The dressing may be a bioactive dressing. The dressing may contain one or more active compounds such as a growth factor, an antimicrobial (e.g. antibiotic / antibacterial) agent and / or an enzyme (e.g. to aid in necrotic tissue removal). The dressing may contain a natural bioactive polymer such as collagen, chitosan, hyaluronic acid, and / or pectin. Such polymers may facilitate cell migration, support angiogenesis, and / or promote tissue regeneration. The dressing may be a drug-loaded dressing. The dressing may comprise a hydrocolloid, hydrogel, alginate, foam, and / or film, for example which incorporates an anti-microbial agent, an anti-inflammatorily agent and / or an analgesic agent. The dressing may comprise graphene and / or silver to aid in preventing, ameliorating, or treating microbial infections.

[0050] The present invention allows the prevention, amelioration and / or treatment of medical device-associated bacterial infections by providing the H2S at a controlled rate and over a prolonged period. For example, the composition of the present invention offers the possibility to effectively reduce catheter-related bacterial infections.

[0051] The article may be an implant. The implant may be permanent or non-permanent. Implants may be a graft (e.g. vascular bypass graft), an (artificial) heart valve, a voice prosthesis, a prosthetic joint, an artificial lens, a stent (e.g. vascular stent), a shunt (e.g. hydrocephalus shunt), a pacemaker (e.g. pacemaker lead), a drain tube, an endotracheal tube, a gastrointestinal tube, a (surgical) pin, a guidewire, a (surgical) staple, a cannula, a subcutaneous or transcutaneous port, an indwelling catheter, a catheter connector, and / or a contact lens. Preferably the article is an implant that is an (artificial) heart valve, a stent (e.g. vascular stent), a pacemaker (e.g. pacemaker lead), a cannula, a subcutaneous or transcutaneous port, a catheter, and / or a catheter connector.

[0052] The article may be a catheter, such as a urinary (e.g. transurethral or suprapubic) catheter and / or a vascular (e.g., central venous, dialysis (e.g. peritoneal dialysis), peripheral venous, arterial and / or pulmonary artery (e.g. Swan-Ganz) catheter) catheter. The catheter is preferably a vascular catheter, such as a central venous catheter, a dialysis catheter (e.g. peritoneal dialysis catheter), a peripheral venous catheter, an arterial catheter and / or a pulmonary artery catheter (e.g. Swan-Ganz catheter). The article may be a part of a catheter, such as a tube, balloon, and / or connector for a catheter.

[0053] The article may comprise the composition as a surface (or part of a surface) that, In use, will contact tissue of a subject being treated using the article, for example as an outer surface of the article.

[0054] Hydrogen sulfide releasing agent

[0055] A hydrogen sulfide (H2S) releasing agent (also known as a H2S donor) is a compound or composition that releases H2S, for example in response to a trigger. Therefore, a H2S releasing agent is able to release H2S.

[0056] The H2S releasing agent may be H2S (e.g. gaseous H2S), an inorganic salt, and / or an organic compound.

[0057] Inorganic salts such as NaSH and Na2S release H2S upon exposure to water (e.g. an aqueous solution). The spontaneous release of H2S when these compounds are contacted with water traditionally makes it challenging to precisely regulate H2S levels. This drawback traditionally leads to rapid and uncontrollable H2S release, which can have adverse effects in vivo. Additionally, H2S can evaporate quickly from the solution under laboratory conditions and becomes undetectable after 12 hours.

[0058] Inorganic salts for use as H2S releasing agents include inorganic sulfide salts, such as NaSH, Na2S and / or CaS. Organic H2S releasing agents, such as polysulfides including DATS, can traditionally produce H2S in a slower and more controllable manner than inorganic sulfide salts, such as Na2S. DATS is a naturally occurring organosulfur compound found in garlic, known for its potent antioxidant, anticancer, antimicrobial, and cardiovascular protective properties.

[0059] Organic compounds for use as H2S releasing agents may include a sulfur(II)-containing functional group, such as a sulfide (e.g. a monosulfide, disulfide, trisulfide and / or polysulfide), an allyl sulfide (e.g. diallyl sulfide (DAS), diallyl disulfide (DADS), diallyl trisulfide (DATS), dipropyl disulfide (DPDS) and / or allyl methyl sulfide (AMS)), a thiosulfinate (e.g. diallyl thiosulfinate, allicin), an S-aroylthiooxime (SATO, e.g. a SATO disclosed by Org. Lett. 2014, 16, 6, 1558-1561), a 1, 2-dithiole-3-thione (DTT, e.g. ATB-337, ATB-429, HS-SUL, HS-NAP, HA-ASA and / or HS-IBU), an N- (benzoylthio)benzamide, a perthiol (e.g. a cysteine- and / or penicillamine-based perthiol), a dithioperoxyanhydride, an arylthioamide, a gem-dithiol, a ketoprofenate- cage, a thioamino acid (such as thioglycine and / or thiovaline). Organic compounds for use as H2S releasing agents include 2,4-bis(4-methoxyphenyl)- l,3,2,4-dithiadiphosphetane-2,4-disulfide (Lawesson’s reagent), a phosphinodithioate (e.g. morpholin-4-ium 4-methoxyphenyl(morpholino)phosphinodithioate, GYY4137), a phosphorodithioate, and a phosphonamidothioate (JK donor, e.g. JK-1 (Yang et al., J Cell Mol Med. 2017; 21(10):2441-2451)). The H2S releasing agent may be one described by Chem Commun. 2014 Oct 14; 50(80): 11788-11805 and / or the references therein.

[0060] The release of H2S may be detected and / or measured by methylene blue (MB) assay, ion selective electrodes (ISE), fluorescence-based assays and / or gas chromatography (Zhao et al., Chem Commun. 2014; 50(80): 11788-11805).

[0061] The composition may comprise the hydrogen sulfide releasing agent in a proportion of 0.001 wt% or more, or 0.01 wt% or more, such as 0. 1 wt% or more, or 0.2 wt% or more, or 0.3 wt% or more, or 0.4 wt% or more, or 0.45 wt% or more relative to the weight of the whole composition. The composition may comprise the hydrogen sulfide releasing agent in a proportion of 40 wt% or less, such as 20 wt% or less, or 10 wt% or less, for example 5.0 wt% or less, or 4.0 wt% or less, such as 3.0 wt% or less, or 2.0 wt% or less relative to the weight of the whole composition. The composition may comprise the hydrogen sulfide releasing agent in a proportion of from 0.001 wt% to 40 wt%, such as from 0.1 to 10 wt%, or from 0.2 to 5 wt% relative to the weight of the whole composition.

[0062] The composition may comprise the H2S releasing agent in a proportion of 0.01 wt% or more, or 0.1 wt% or more, or 0.5 wt% or more, such as 1 wt% or more, such as 10wt% or more, or 30 wt% or more, or 50 wt% or more, for example 60 wt% or more, or 70 wt% or more, or 80 wt% or more, relative to the weight of the graphene-based material. The composition may comprise the EESreleasing agent in a proportion of 1000 wt% or less, or 800 wt% or less, or 400 wt% or less, such as 200 wt% or less, or 100 wt% or less, for example 90 wt% or less, relative to the weight of the graphene-based material. The composition may comprise the hydrogen sulfide releasing agent in a proportion of from 0.01 to 1000 wt%, such as from 10 to 400 wt%, or from 50 to 200 wt%, such as from 70 to 100 wt%, relative to the weight of graphene-based material. The composition may comprise the hydrogen sulfide releasing agent in a proportion of O.OOlmmol / g or more, relative to the weight of the graphene-based material, for example 0.005 mmol / g or more, or 0.01 mmol / g or more, for example 0.05 mmol / g or more, for example 0.1 mmol / g or more, such as 0.12 mmol / g or more, or 1.0 mmol / g or more. The composition may comprise the H2S releasing agent in a proportion of 50 mmol / g or less, relative to the weight of the graphene-based material, such as 20 mmol / g or less, or 10 mmol / g or less, for example 7 mmol / g or less, or 5 mmol / g or less. The composition may comprise the hydrogen sulfide releasing agent in a proportion of from 0.001 to 50 mmol / g, relative to the weight of the graphene-based material, such as from 0.01 to 10 mmol / g.

[0063] Graphene-based material

[0064] The graphene-based material may be selected from the list consisting of graphene oxide, graphene (e.g. porous graphene) and reduced graphene oxide. Preferably the graphenebased material is graphene oxide.

[0065] Graphene oxide (GO) contains functional groups such as carboxyl (COOH) carbonyl (C=C), hydroxyl (OH) and epoxy groups (R-O-CH2- CH2 ) which allow the attachment of drugs or molecules (e.g. hydrogen sulfide) via covalent and non-covalent methods.

[0066] Graphene oxide (GO) is a graphene derivate characterized by a significant presence of oxygen bonds along its edges and defective regions which promote interactions with biomolecules. These include epoxy (-O-O-), carboxylic (-COOH), carbonyl (-C=O), and hydroxyl (OH) groups on both accessible sides. GO, in contrast to pristine graphene, is hydrophilic and offers excellent aqueous processability while retaining its amphiphilicity and surface functionalization capabilities. GO has extraordinary mechanical and physical properties, and the ability to be chemically modified.

[0067] Graphene oxide is preferably prepared from graphite flakes by Hummer’s modified method.

[0068] The composition may comprise graphene-based material (e.g. graphene oxide) in a proportion of 0.001 wt% or more, or 0.01 wt% or more, such as 0.1 wt% or more, or 0.2 wt% or more, or 0.3 wt% or more, or 0.4 wt% or more, or 0.5 wt% or more, or 0.55 wt% or more, relative to the weight of the whole composition. The composition may comprise the graphene-based material in a proportion of 40 wt% or less, such as 20 wt% or less, or 10 wt% or less, for example 5.0 wt% or less, or 4.0 wt% or less, such as 3.0 wt% or less, or 2.5 wt% or less relative to the weight of the whole composition. The composition may comprise the graphene-based material in a proportion of from 0.001 wt% to 40 wt%, such as from 0.1 to 10 wt%, or from 0.2 to 5 wt% relative to the weight of the whole composition.

[0069] The composition may comprise the graphene-based material (e.g. graphene oxide) in a proportion of 1 wt% or more, such as 10wt% or more, or 30 wt% or more, or 50 wt% or more, for example 80 wt% or more, or 100 wt% or more, or 110 wt% or more, such as 120 wt% or more, relative to the weight of the hydrogen sulfide releasing agent. The composition may comprise the graphene-based material in a proportion of 2000 wt% or less, or 1000 wt% or less, or 600 wt% or less, such as 300 wt% or less, or 200 wt% or less, for example 150 wt% or less, relative to the weight of the hydrogen sulfide releasing agent. The composition may comprise the graphene-based material in a proportion of from 1 to 2000 wt%, such as from 10 to 600 wt%, or from 50 to 300 wt%, such as from 80 to 200 wt%, relative to the weight of hydrogen sulfide releasing agent.

[0070] Polymer

[0071] The polymer may be natural and / or synthetic. Preferably the polymer is biocompatible (e.g. non-cytotoxic).

[0072] Natural polymers find extensive use in medical and pharmaceutical fields due to their hydrophilicity, biocompatibility, non-toxicity, biodegradability, availability, and costeffectiveness, mucoadhesive, non-immunogenic, mimic extracellular matrix. Suitable natural polymers include chitosan and pectin, which possess inherent antibacterial properties, making them excellent for wound dressing applications. Other suitable natural polymers include those selected from the list consisting of chitosan (CS), hyaluronic acid (HA), starch (St), silk fibroin (SF), keratin, sodium alginate (SA), gelatin (GE), collagen (Col), pectin (Pec), cellulose, cellulose acetate, and celluloid (cellulose nitrate).

[0073] Synthetic polymers such as polypropylene (PP) have been widely used for wound dressing materials. Other synthetic polymers have received approval from the FDA for biomedical uses due to their good biocompatibility, biodegradability and non-toxic properties, such as poly caprolactone (poly(a-caprolactone), PCL), polyethylene glycol (PEG), polyethylene oxide (PEO), polyurethane (PU), poly(vinyl alcohol) (PVA), poly(lactic acid) (PLA), poly-3 -hydroybutyrate, and poly(lactic-co-glycolic acid) (PLGA), and polyglycolide (PGA).

[0074] Preferably the polymer is PCL. The characteristics of PCL make it an excellent candidate for long-term drug delivery system in wound dressing applications. PCL has demonstrated good processability in the creation of nanofibers used to manufacture wound dressings. Its degradability can be controlled through molecular weight, shape, and chemical adjustment, hence, enables the controlled release of growth factors, antibacterial substance, and other bioactive agents. It is non-toxic, highly soluble at room temperature, hydrophobic, easy processable, low-cost, mimic ECM, bioresorbable, PDA approved and biodegradable. Furthermore, PCL is recognised as an exceptional hydrophobic polymer, enhancing its adsorption and moisture-wicking properties.

[0075] Wound dressings provide support to surroundings tissue and must be flexible and compressible, yet possess the necessary durability to withstand abrasive shear, torsion, tension, and compression forces. PCL has a good elongation, a moderate level of strength, low yield strength and high toughness material.

[0076] Another important requirement in a polymer material for wound dressing applications is permeability. Permeability may refer to the ability of a substance or material to enable the passage or movement of another substance through it. The hydrophobic characteristics of PCL results in high permeability which has been exploited for delivery of low molecular weight molecules. The permeability of PCL can be tuned by adapting the porosity of fibre during the fibre formation process.

[0077] PCL may, for example, be spun (e.g. using pressurised gyration apparatus) or electrospun. Electrospinning is useful for coating other fibres, and is particularly useful for slowing the release of the hydrogen sulfide. Electrospun fibres tend to be more fine and can provide slower release than conventionally spun fibres. Conventionally spinning fibres is more efficient (faster) as it yields more deposit per unit time and does not involve the use of high-voltage electric fields. Thus, a combination of conventionally spun and electrospun fibres can be useful in the formation of a slow release composite.

[0078] The composition may comprise the polymer in a proportion of 20 wt% or more, such as 40 wt% or more, or 60 wt% or more, or 80 wt% or more, such as 90 wt% or more, or 94 wt% or more, or 95 wt% or more, such as 96 wt% or more, relative to the weight of the whole composition. The composition may comprise the polymer in a proportion of 99.99wt% or less, such as 99.9 wt% or less, or 99.8 wt% or less, such as 99.6 wt% or less, or 99.4 wt% or less, or 99.2 wt% or less, or 99.0 wt% or less, or 98.8 wt% or less, or 98.5 wt% or less, such as 98.0 wt% or less, relative to the weight of the whole composition. The composition may comprise the polymer in a proportion of from 20 to 99.99 wt%, such as from 80 to 99.8 wt%, or from 90 to 99.5 wt%, relative to the weight of the whole composition.

[0079] Preferred Embodiments

[0080] In one embodiment of the present disclosure: the hydrogen sulfide releasing agent is an inorganic sulfide salt and / or an organic compound comprising a sulfur (Il)-containing functional group; the graphene-based material is graphene oxide, graphene (e.g. porous graphene) and / or reduced graphene oxide; and the polymer is a polyester and / or a cellulose based polymer

[0081] In one embodiment of the present disclosure: the hydrogen sulfide releasing agent is an inorganic sulfide salt (e.g. NaSH, Na2S and / or CaS) and / or an organic compound comprising a group selected from the list consisting of: a sulfide, an allyl sulfide, a phosphinodithioate, a thiosulfinate, an S-aroylthiooxime, a 1, 2-dithiole-3-thione, a phosphorodithioate, a phosphonamidothioate, an N-(benzoylthio)benzamide, a perthiol, a dithioperoxyanhydride, an arylthioamide, a gem-dithiol, a ketoprofenate-cage, and a thioamino acid; the graphene-based material is graphene oxide, graphene (e.g. porous graphene) and / or reduced graphene oxide; and the polymer is a polyester and / or a cellulose based polymer In one embodiment of the present disclosure: the hydrogen sulfide releasing agent is an inorganic sulfide salt (e.g. NaSH, Na2S and / or CaS) and / or an organic compound selected from the list consisting of: diallyl sulfide (DAS), diallyl disulfide (DADS), diallyl trisulfide (DATS), dipropyl disulfide (DPDS), allyl methyl sulfide (AMS), diallyl thiosulfinate, allicin, a SATO disclosed by Org. Lett. 2014, 16, 6, 1558-1561, ATB-337, ATB-429, HS-SUL, HS-NAP, HA-ASA and HS-IBU, thioglycine, thiovaline, 2,4-bis(4-methoxyphenyl)-l,3,2,4-dithiadiphosphetane-2,4-disulfide (Lawesson’s reagent), morpholin-4-ium 4- methoxyphenyl(morpholino)phosphinodithioate, GYY4137, and JK-1 ; the graphene-based material is graphene oxide, graphene (e.g. porous graphene) and / or reduced graphene oxide; and the polymer is polycaprolactone (PCL), poly-3 -hydroybutyrate, polylactic acid, cellulose acetate and / or celluloid.

[0082] In one embodiment of the present disclosure: the hydrogen sulfide releasing agent is an inorganic sulfide salt (e.g. NaSH, Na2S and / or CaS) and / or an organic compound selected from the list consisting of: diallyl sulfide (DAS), diallyl disulfide (DADS), diallyl trisulfide (DATS), dipropyl disulfide (DPDS), allyl methyl sulfide (AMS), diallyl thiosulfinate, allicin, a SATO disclosed by Org. Lett. 2014, 16, 6, 1558-1561, ATB-337, ATB-429, HS-SUL, HS-NAP, HA-ASA and HS-IBU, thioglycine, thiovaline, 2,4-bis(4-methoxyphenyl)-l,3,2,4-dithiadiphosphetane-2,4-disulfide (Lawesson’s reagent), morpholin-4-ium 4- methoxyphenyl(morpholino)phosphinodithioate, GYY4137, and JK-1 ; the graphene-based material is graphene oxide; and the polymer is polycaprolactone (PCL), poly-3 -hydroybutyrate and / or polylactic acid.

[0083] In one embodiment of the present disclosure: the hydrogen sulfide releasing agent is Na2S and / or diallyl trisulfide (DATS); the graphene-based material is graphene oxide; and the polymer is PCL. In one embodiment, the article is a medical device (e.g. a wound dressing (e.g. a bandage and / or gauze), a catheter, and / or an implant (such as a heart valve)), and: the hydrogen sulfide releasing agent is an inorganic sulfide salt (e.g. NaSH, Na2S and / or CaS) and / or an organic compound comprising a group selected from the list consisting of: a sulfide, an allyl sulfide, a phosphinodithioate, a thiosulfinate, an S-aroylthiooxime, a 1, 2-dithiole-3-thione, a phosphorodithioate, a phosphonamidothioate, an N-(benzoylthio)benzamide, a perthiol, a dithioperoxyanhydride, an arylthioamide, a gem-dithiol, a ketoprofenate-cage, and a thioamino acid; the graphene-based material is graphene oxide, graphene (e.g. porous graphene) and / or reduced graphene oxide; and the polymer is a polyester and / or a cellulose based polymer.

[0084] In one embodiment, the article is a medical device (e.g. a wound dressing (e.g. a bandage and / or gauze), a catheter, and / or an implant (such as a heart valve)), and: the hydrogen sulfide releasing agent is an inorganic sulfide salt (e.g. NaSH, Na2S and / or CaS) and / or an organic compound comprising a group selected from the list consisting of: a sulfide, an allyl sulfide, a phosphinodithioate, a thiosulfinate, an S-aroylthiooxime, a 1, 2-dithiole-3-thione, a phosphorodithioate, a phosphonamidothioate, an N-(benzoylthio)benzamide, a perthiol, a dithioperoxyanhydride, an arylthioamide, a gem-dithiol, a ketoprofenate-cage, and a thioamino acid; the graphene-based material is graphene oxide, graphene (e.g. porous graphene) and / or reduced graphene oxide; the polymer is a polyester and / or a cellulose based polymer; and the article comprises one or more surface (e.g. sheath) layer(s) of polymer and one or more core layer(s) of the composition.

[0085] In one embodiment the composition comprises: the hydrogen sulfide releasing agent (e.g. Na2S and / or diallyl trisulfide) in a proportion of 0.001 wt% or more; graphene-based material (e.g. graphene oxide) in a proportion of 0.001 wt% or more; and polymer (e.g. PCL) in a proportion of 20 wt% or more. In one embodiment the composition comprises: the hydrogen sulfide releasing agent (e.g. Na2S and / or diallyl trisulfide) in a proportion of 0.001 wt% to 40 wt%; graphene-based material (e.g. graphene oxide) in a proportion of from 0.001 wt% to 40 wt%; and polymer (e.g. PCL) in a proportion of the polymer in a proportion of from 20 to 99.99 wt%.

[0086] In one embodiment the composition comprises: the hydrogen sulfide releasing agent (e.g. Na2S and / or diallyl trisulfide) in a proportion of 0.1 to 10 wt%; graphene-based material (e.g. graphene oxide) in a proportion of from 0.1 to 10 wt%; and polymer (e.g. PCL) in a proportion of the polymer in a proportion of from 80 to 99.8 wt%.

[0087] In one embodiment: the hydrogen sulfide releasing agent is an inorganic sulfide salt (e.g. NaSH, Na2S and / or CaS) and / or an organic compound selected from the list consisting of: diallyl sulfide (DAS), diallyl disulfide (DADS), diallyl trisulfide (DATS), dipropyl disulfide (DPDS), allyl methyl sulfide (AMS), diallyl thiosulfinate, allicin, a SATO disclosed by Org. Lett. 2014, 16, 6, 1558-1561, ATB-337, ATB-429, HS-SUL, HS-NAP, HA-ASA and HS-IBU, thioglycine, thiovaline, 2,4-bis(4-methoxyphenyl)-l,3,2,4-dithiadiphosphetane-2,4-disulfide (Lawesson’s reagent), morpholin-4-ium 4-methoxyphenyl(morpholino) phosphinodithioate, GYY4137, and JK-1 ; the graphene-based material is graphene oxide; the polymer is polycaprolactone (PCL), poly-3 -hydroybutyrate and / or polylactic acid; the composition comprises the hydrogen sulfide releasing agent (e.g. Na2S and / or diallyl trisulfide) in a proportion of 0.1 to 10 wt%; the composition comprises graphene-based material (e.g. graphene oxide) in a proportion of from 0.1 to 10 wt%; and the composition comprises polymer (e.g. PCL) in a proportion of the polymer in a proportion of from 80 to 99.8 wt%. Medical Uses and Pharmaceutical Compositions

[0088] H2S exhibits antiatherosclerotic, vasodilator, and proangiogenic properties, and protects the kidney and heart from damage following ischemia / reperfusion injury. Hydrogen sulfide is known to be useful in the prevention, amelioration or treatment of microbial (e.g. bacterial) infections (e.g. the treatment of a wound), myocardial infarction (e.g. acute myocardial infarction), hypertension (e.g. arterial and / or pulmonary hypertension), peripheral arterial disease, cardiovascular diseases, atherosclerosis, ischemia reperfusion, heart failure, peptic ulcer disease, acute and / or chronic inflammatory diseases (e.g. autoimmune diseases (e.g. (organ) transplant rejection), arthritis (e.g. rheumatoid arthritis), lupus, fibromyalgia, and chronic fatigue syndrome), diabetes, diabetic kidney disease, gastric ulcers (e.g. the prevention of gastric ulcers during anti-inflammatory treatment), metabolic syndrome, stroke (especially ischemic stroke), inflammatory bowel disease, cancer (e.g. prostate, breast, lung, colon and brain (e.g. glioblastoma) cancer), neurological disorders / diseases, ethylmalonic encephalopathy, Parkinson’s disease, Alzheimer’s disease, and erectile dysfunction. Antioxid Redox Signal. 2012 Jul 1; 17(1): 119-140. Preferably the composition is for the treatment of a disease or condition selected from the list consisting of: a microbial (e.g. bacterial) infection, a cardiovascular disease, an inflammatory disease, a cancer, and a neurological disease or disorder. More preferably the composition is for the treatment of a disease or condition that is a bacterial infection or a cardiovascular disease.

[0089] In one embodiment the pharmaceutical composition (e.g. formulation) comprises at least one active compound of the invention together with one or more pharmaceutically acceptable carriers, adjuvants, excipients, diluents, fillers, buffers, stabilisers, preservatives, lubricants, or other materials well known to those skilled in the art and optionally other therapeutic or prophylactic agents.

[0090] To prepare the pharmaceutical compositions of this invention, an effective amount of a compound of the present invention, as the active ingredient is combined in intimate admixture with a pharmaceutically acceptable carrier, which carrier may take a wide variety of forms depending on the form of preparation desired for administration. These pharmaceutical compositions may be suitable for parenteral administration (e.g. intravenous), ophthalmic administration, otic administration, rectal administration, intra-vaginal administration, transdermal administration, topical administration, oral administration, rectal administration (for example, by enema, suppository, or catheter), or nasally (for example, endoscopically, or through a nasogastric or nasoduodenal tube).

[0091] Liquid diluents and / or carriers include water, glycol, an oil, an alcohol. Solid diluents and / or carriers include a starch, a sugar, kaolin, a lubricant, a binder, a disintegrating agent.

[0092] The pharmaceutical composition may be for oral administration, for example as a solution, a suspension, a film, a tablet, a chew, a powder, granules, an emulsion, an elixir, a syrup, a paste and / or a capsule.

[0093] Preferably the pharmaceutical composition is for topical application. The formulation may therefore be formulated as a solution, foam, suspension, cream, ointment, paste, lotion, spray, powder, patch, dressing, or gel.

[0094] Pharmaceutical compositions can be formulated in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used in the specification and claims herein refers to physically discrete units suitable as unitary dosages, each unit containing a predetermined quantity of active ingredient, calculated to produce the desired therapeutic effect, in association with the required pharmaceutical carrier. Examples of such dosage unit forms are tablets (including scored or coated tablets), capsules, pills, powder packets, wafers, injectable solutions or suspensions, teaspoonfuls, tablespoonfuls and the like, and segregated multiples thereof.

[0095] The composition according to the invention may be administered to a human or to an animal, which may be a mammal, e.g. it may be a farm animal, or an animal kept as a pet, such as a dog, cat, or horse. A subject may be administered an amount of the composition that is effective to prevent, ameliorate and / or treat the disease or condition.

[0096] The pharmaceutical composition may comprise the composition in an amount of 0.0001 wt% or more, such as 0.01 wt% or more, such as from 0.0001 wt% to 50 wt%, or from 0.01 wt% to 10 wt%. The pharmaceutical composition may comprise the carrier and / or diluent in an amount of 0.1 wt% or more, such as 10 wt% or more, for example in an amount of from 0.1 wt% to 99.9999 wt%, or from 10 wt% to 99.99 wt%.

[0097] Manufacture

[0098] The eighth aspect provides a method of preparation of a fibre composite, wherein the method comprises: providing a liquid mixture (e.g. solution and / or suspension), wherein the liquid mixture comprises a polymer, graphene-based material loaded with a hydrogen sulfide releasing agent, and a solvent; spinning the liquid mixture in a vessel (i.e. rotating the vessel about a central axis while the liquid mixture is in the vessel), wherein the vessel comprises an orifice on the radially outermost wall, such that the liquid mixture escapes from the vessel through the orifice so as to form the fibre composite.

[0099] Spinning / gyration (centrifugal spinning) can enable the large-scale production of fibres while enhancing control over the product morphology. Pressurised gyration apparatus is shown by Figure 1 of the accompanying drawings. Preferably the present invention does not apply pressure during gyration. The vessel may be subjected to a pressure of atmospheric pressure (lOOkPa) ±50% or less, such as of atmospheric pressure ±10% or less.

[0100] The method may comprise a step of preparing the graphene-based material loaded with a hydrogen sulfide releasing agent. This step may comprise combining (e.g. mixing) graphene-based material and the hydrogen sulfide releasing agent in a solvent (e.g. water). The graphene-based material and hydrogen sulfide releasing agent may be left in the water for a period of 1 hour or more, such as 6 hours or more, or 12 hours or more (e.g. from 1 hour to 2 weeks, or from 6 hours to 48 hours). The hydrogen sulfide releasing agent will sorb onto the graphene-based material. The method may comprise separating the graphene-based material loaded with hydrogen sulfide releasing agent from the solvent (e.g. water), for example by filtration, centrifugation and / or lyophilisation. Preferably the separation is performed by centrifugation. Following separation, the loaded graphene-based material may be dried (e.g. at room temperature, 15-30°C). The method may comprise a step of preparing the liquid mixture that comprises a polymer, graphene-based material loaded with a hydrogen sulfide releasing agent, and a solvent. This step may comprise contacting the solvent with the polymer, and contacting the solvent with the loaded graphene-based material . This step may comprise subjecting the mixture of the polymer, the loaded graphene-based material, and the solvent to sonication in order to homogenise the liquid mixture.

[0101] Preferably the polymer is dissolved in the solvent. Preferably the loaded graphene-based material is either dissolved or suspended in the solvent.

[0102] The solvent may be an organic solvent. Preferably the solvent is a volatile organic solvent. The solvent may be a mixture of two or more solvents. Preferably the solvent is selected from the list consisting of: alcohols (e.g. methanol, ethanol, propanol or butanol), methylene chloride, chloroform, 1,2-dichloroethane, tetrahydrofuran, ethyl acetate, isopropyl acetate, acetone, acetonitrile, benzene, an alkane (e.g. pentane, cyclopentane, hexane, cyclohexane, or heptane), triethylamine, 1,2-dimethoxyethane, butanone, methyl t-butyl ether, or a mixture thereof. Preferably the solvent is a mixture of an alcohol (e.g. methanol, ethanol, propanol, or butanol) and a chlorinated solvent (e.g. methylene chloride, chloroform or 1,2-dichloroethane), such as a mixture of methanol and chloroform (e.g. in a volume ratio of 1 :3).

[0103] The vessel may be for pressurised gyration. The vessel may be substantially cylindrical. The vessel may comprise one or more orifices that, in use, the liquid mixture escapes through, from the vessel, so as to form the fibre composite. The gyration / rotation of the vessel may be at a speed / rate of 5000rpm or more, such as 10000 rpm or more, or 20000 rpm or more, such as 30000 rpm or more. The gyration / rotation of the vessel may be at a speed / rate of 100000 rpm or less, such as 50000rpm or less, or 40000rpm or less. The gyration / rotation of the vessel may be at a speed / rate of from 5000 to lOOOOOrpm, such as from 20000 to 50000rpm. The or each orifice may be substantially cylindrical in shape. The or each orifice may have a diameter of 0. 1mm to 1.0mm, such as from 0.3mm to 0.7mm, or from 0.4mm to 0.6mm.

[0104] The gyration and release of the liquid mixture may be performed at a temperature around room temperature, such as 10-40°C, or 15-30°C. The disclosure includes the subject-matter of the following clauses:

[0105] 1. An article formed of a composition, wherein the composition comprises: a hydrogen sulfide releasing agent, a graphene-based material, and polymer, and wherein the hydrogen sulfide releasing agent and the graphene-based material are encapsulated within the polymer.

[0106] 2. The article of clause 1, wherein the graphene-based material is graphene oxide, graphene and / or reduced graphene oxide.

[0107] 3. The article of clause 1 or clause 2, wherein the hydrogen sulfide releasing agent is an inorganic sulfide salt and / or an organic compound comprising a group selected from the list consisting of: a sulfide, an allyl sulfide, a phosphinodithioate, a thiosulfinate, an S-aroylthiooxime, a 1, 2-dithiole-3-thione, a phosphorodithioate, a phosphonamidothioate, an N-(benzoylthio)benzamide, a perthiol, a dithioperoxyanhydride, an arylthioamide, a gem-dithiol, a ketoprofenate-cage, and a thioamino acid.

[0108] 4. The article of clause 3, wherein the hydrogen sulfide releasing agent is Na2S and / or DATS.

[0109] 5. The article of any preceding clause, wherein the polymer is a polyester and / or a cellulose based polymer.

[0110] 6. The article of clause 5, wherein the polymer is selected from the list consisting of: polycaprolactone, poly-3 -hydroybutyrate, polylactic acid, cellulose acetate, and celluloid.

[0111] 7. The article of any preceding clause, wherein the composition is present as fibres.

[0112] 8. The article of any preceding clause, wherein the article comprises one or more surface layer of polymer and one or more core layer of the composition.

[0113] 9. The article of any preceding clause, wherein the article is a medical device.

[0114] 10. The article of clause 9, wherein the medical device is a wound dressing, a catheter, and / or an implant.

[0115] 11. The article of any preceding clause, wherein the composition comprises the hydrogen sulfide releasing agent in a proportion of 0.1 to 10 wt%.

[0116] 12. The article of any preceding clause, wherein the composition comprises the graphene-based material in a proportion of from 0.1 to 10 wt%.

[0117] 13. The article of any preceding clause, wherein the composition comprises the polymer in a proportion of the polymer in a proportion of from 80 to 99.8 wt%.

[0118] 14. The article of any preceding clause, wherein: the hydrogen sulfide releasing agent is an inorganic sulfide salt and / or an organic compound selected from the list consisting of: diallyl sulfide, diallyl disulfide, diallyl trisulfide, dipropyl disulfide, allyl methyl sulfide, diallyl thiosulfinate, allicin, a SATO disclosed by Org. Lett. 2014, 16, 6, 1558— 1561, ATB-337, ATB-429, HS-SUL, HS-NAP, HA-ASA and HS-IBU, thioglycine, thiovaline, 2,4-bis(4-methoxyphenyl)-l,3,2,4-dithiadiphosphetane-2,4-disulfide (Lawesson’s reagent), morpholin-4-ium 4-methoxyphenyl(morpholino) phosphinodithioate, GYY4137, and JK-1; the graphene-based material is graphene oxide; the polymer is polycaprolactone, poly-3 -hydroybutyrate and / or polylactic acid; the composition comprises the hydrogen sulfide releasing agent in a proportion of 0.1 to 10 wt%; the composition comprises graphene-based material in a proportion of from 0.1 to 10 wt%; and the composition comprises polymer in a proportion of the polymer in a proportion of from 80 to 99.8 wt%.

[0119] 15. The article of any preceding clause, wherein: the hydrogen sulfide releasing agent is Na2S and / or diallyl trisulfide; the graphene-based material is graphene oxide; the polymer is polycaprolactone (PCL), poly-3 -hydroybutyrate and / or polylactic acid; the composition comprises the hydrogen sulfide releasing agent in a proportion of 0.1 to 10 wt%; the composition comprises graphene-based material in a proportion of from 0.1 to 10 wt%; and the composition comprises polymer in a proportion of the polymer in a proportion of from 80 to 99.8 wt%.

[0120] 16. A composition comprising: a hydrogen sulfide releasing agent, graphene-based material, and polymer, and wherein the hydrogen sulfide releasing agent and the graphene-based material are encapsulated within polymer.

[0121] 17. A composition as defined by clause 16 for use as a medicament.

[0122] 18. A composition as defined by clause 16 for use in the prevention, amelioration and / or treatment of a hydrogen sulfide-responsive disease or condition.

[0123] 19. The composition for use of clause 16, wherein the hydrogen sulfide-responsive disease or condition is selected from the list consisting of: a microbial infection, myocardial infarction, hypertension, peripheral arterial disease, cardiovascular diseases, atherosclerosis, ischemia reperfusion, heart failure, peptic ulcer disease, acute and / or chronic inflammatory diseases, diabetes, diabetic kidney disease, gastric ulcers, metabolic syndrome, stroke, inflammatory bowel disease, cancer, neurological disorders / diseases, ethylmalonic encephalopathy, Parkinson's disease, Alzheimer's disease, and erectile dysfunction.

[0124] 20. A pharmaceutical composition comprising the composition of the clause 16 and a pharmaceutically acceptable carrier and / or diluent. 21. A method of preparation of a fibre composite, wherein the method comprises: providing a liquid mixture (e.g. solution and / or suspension), wherein the liquid mixture comprises a polymer, graphene-based material loaded with a hydrogen sulfide releasing agent, and a solvent; and spinning the liquid mixture in a vessel, wherein the vessel comprises an orifice on the radially outermost wall, such that the liquid mixture escapes from the vessel through the orifice so as to form the fibre composite.

[0125] 22. The method of clause 21, wherein the rotation of the vessel may be at a rate of 5000rpm or more.

[0126] Examples

[0127] Materials

[0128] Polycaprolactone pellets (PCL, Mn= 80,000 g / mol, Sigma Aldrich), acetone (99.5%, Sigma Aldrich), chloroform (99.0-99.4%, Sigma Aldrich), methanol (99.8%, Sigma Aldrich), phosphate buffered saline (PBS, tablet, pH 7.4, Sigma Aldrich), N,N- dimethyl-p-phenyl-enediamine dihydrochloride (DMPD, Sigma Aldrich), ferric chloride (FeCL, Sigma Aldrich), zinc acetate (Zn(OAc)2, ThermoFisher Scientific), diallyl trisulfide (DATS, Sigma Aldrich), sodium sulfide (Na2S, Sigma Aldrich).

[0129] Preparation of PCL fibres

[0130] PCL-based nanofibers were fabricated through electrospinning technique using a 18G stainless steel needle (1.2mm) connected to a syringe (10 ml) through a capillary tube. The needle was connected to a voltage supplier, and then positioned at a distance of 15cm from the metallic collector which was previously covered in aluminium foil.

[0131] Three different polymeric solutions with different concentrations of PCL (8, 10 and 12 w / v%) in acetone (20mL) were prepared separately by stirring the PCL and acetone at 50°C for 24 hours. A volume of 5 mL of each solution was loaded into the syringe. Electrospinning was performed at a flow rate of 0.3 mL / min, voltage of 22 kV, temperature of 22-23 °C, and humidity of 40-43 %. The resulting electrospun fibres were characterized with an optical microscope and Image J software.

[0132] Preparation of Na2S or DATS-functionalized graphene oxide

[0133] The synthesis of DATS-GO was carried out by a modification of previous methods (Sun et al., J. Mater. Chem. B, 2015, 3, 4451-4457). Briefly, graphene oxide (GO, 300 mg) was added in 60 mL of distilled water. Then, 250 mg of DATS were added into the GO dispersion. The resulting mixture of a drug / carrier (0.8 / 1) was stirred at room temperature and left it overnight. The solution was placed into a centrifuge (3234 rpm, 25 min, 10°C) and DATS-conjugated GO particles were collected. DATS-GO particles were dried at room temperature for 5 days.

[0134] Na2S-GO was synthesized to achieve a controllable release of H2S by a modification protocol of previous procedure (He et al., 2022, Applied Materials Today, 26, p. 101313). Briefly, GO (10 mg) was added in a beaker filled with distilled water (2 mb). Then, Na2S solution (500 pL, 200 pg / mL) was added into the aqueous GO solution and the mixture was placed onto a magnetic stirrer overnight. The resulting solution was washed by centrifugation (3234 rpm, 25min, 10°C) and the Na2S-GO particles were collected. The formed particles were dried at room temperature for 5 days.

[0135] Preparation of PCL and nanocomposite fibres by spinning using pressurised gyration apparatus

[0136] A pressurised gyration apparatus was used without positive gas pressure to form spun pure PCL fibres, PCL / GO, PCL / Na2S-GO and PCL / DATS-GO composite fibres. In this study, the motor connected to the bottom of the vessel and the rotating vessel were protected with a plastic container covered in aluminium foil, and no external gas pressure was applied. The aluminium cylindrical rotating vessel and the drilled holes within its wall measured 60 mm and 0.5 mm in diameter, respectively (Altun et al., (2022) European Polymer Journal, [online] 173: 111300).

[0137] A solution of PCL (15 w / v%) was prepared by dissolving 12g of PCL in a binary solvent of chloroform / methanol (3: 1) with a volume of 80mL. The solution was placed into a magnetic stirrer and then left over night to allow PCL pellets to dissolve. A volume of 2 mL of the polymer solution was placed in the vessel and the formation process was carried out with a rotation speed of 36,000 rpm, temperature of 22-23 °C and humidity of 42%. This procedure was repeated 5 times and the forming polymer fibres, placed between the vessel and the plastic contained, were collected in petri-dishes.

[0138] GO, Na2S-GO and DATS-GO powder were each weighed for 3 different concentrations (1, 2 and 4 w / w%) to prepare a 10 mL suspension with the PCL polymer solution (15 w / v%) as indicated in the table below. Each suspension was placed on an ultrasonic bath for 99 min at 23 °C to achieve a homogenized solution with Branson CPXH Digital Bath 5800.

[0139] Concentration of (loaded)GO GO (g) Na2S-GO DATS-GO PCL solution relative to PCL (w / w%) (g) (g) (mL)

[0140] 1 0.015 0.015 0.015 10

[0141] 2 0.03 0.03 0.03 10

[0142] 4 0.06 0.06 0.06 10

[0143] ImL of the PCL / GO, PCL / Na2S-GO and PCL / DATS-GO suspension were poured, one at the time, into the aluminium vessel and connected to a DC motor that was kept rotating at constant rotation speed of 3600 rpm while no pressure was applied. All the experiments were carried out for 3-5 s and the formed loaded fibre allowed to dry for another 5 sec before collection.

[0144] Figure 2a of the accompanying drawings shows a representative scanning electron micrograph (SEM) of a fibre composition according to the invention, specifically 4 wt% Na2S-GO in PCL.

[0145] Figure 2b of the accompanying drawings shows a representative SEM of another fibre composition according to the invention, specifically 4 wt% DATS-GO in PCL, prepared by pressurised gyration. The fibres appear similar to the fibres of Na2S-GO in PCL shown in Figure 2a.

[0146] This demonstrates that that a variety of H2S releasing agents, including DATS and Na2S, can be successfully conjugated with GO, and the conjugated GO can form composite fibres with PCL.

[0147] Formation of layered wound dressing system

[0148] A solution of PCL (8 w / v%) was prepared using 6.4 g of PCL pellets and dissolved into 80 mL of acetone. The suspension was placed onto a heated magnetic stirrer set at 50°C and left over night for complete dissolution. A volume of 8mL was loaded into the syringe, flow rate was set to 0.3 mL / min and voltage to 22 kV. The temperature and humidity were recorded at 21°C and 50-53 %, respectively. Previously prepared spun PCL “loaded” fibres with GO, Na2S-GO and DATS-GO were placed onto a metal collector plate, covered in aluminium foil, at 15 cm distance from the needle. PCL solution was electrospun for 1 min 30 s so as to deposit the resulting PCL on the top of the loaded fibres. PCL was chosen as protective top layer because its biocompatibility, mechanical properties, and its hydrophobicity which provides minimum adherence to the wound. The middle layer, composed PCL loaded with GO, Na2S-GO and DATS-GO aimed to provide antibacterial properties which every day active dressing should possess.

[0149] Methylene blue assay

[0150] Methylene blue cocktail assay was used to detect hydrogen sulfide released by with pristine graphene oxide (GO), DATS-GO, and Na2S-GO (20,10,5,4.5,3, 1.5,0.5 mg / mL). The optimal optical absorbance of GO stock solution (20 mg / mL) was observed at X= 230nm consequently, standard solutions of 10,5,4.5,3,1.5,0.5 mg / mL optical absorbances were measured.

[0151] No colour change was observed after 20 min of incubation however, a positive relation between the concentration and absorbance was recorded and plotted in a calibration curve .

[0152] The absorbance of stock solution of DATS-GO and Na2S-GO (20 mg / mL) was detected at X= 436 nm after 20 min of incubation and a bright pink colour was observed which disappeared after the incubation time. These results did not comply with previous investigations but a change in wavelength and colour compared to GO solution mixture has been attributed to the presence of additional compounds in GO.

[0153] The absorbance of stock and standard solutions of both compounds (Na2S and DATS) were recorded and plotted them in a calibration curve. As previously seen in GO calibrations curve, a straight and positive relation between absorbance and concentration has been observed.

[0154] To determine the concentration of Na2S and DATS in GO stock and standard solutions with known concentrations of Na2S and DATS should be prepared, and their absorption should be measure at the =436 nm. Concentrations of DATS-GO and Na2S-GO at 1, 2, 4 w / w % that correspond to 1.5, 3 and 4.5 mg / mL were chosen for the formation of fibre composites.

[0155] The real-time H2S release from DATS-GO and from Na2S-GO was monitored by methylene blue dye. The results showed the continued release of H2S from the graphene oxide over almost 1 h with release rate of 300 pM per mg conjugate when in contact with moisture.

[0156] Characterization of electrospun PCL nanofibers

[0157] Electrospun PCL nanofibers possess a high surface / contact area and provide a suitable tool as drug delivery system for use in wound treatment, such as antibacterial drugs.

[0158] The morphology of electrospun PCL fibre at different concentrations (8, 10 and 12 w / v%) were characterized by Optical microscopy, the fibre diameters were measured by ImageJ. The mean fibre diameter for 8, 10 and 12 w / v% were found to be 0.046, 0.222 and 0.890, respectively. An increasing trend in diameter was observed which was attributed to the increase of polymer concentration in solution.

[0159] Characterization of PCL (spun using pressurised gyration apparatus). PCL-GO. PCL / GO-Na2S and PCL / GO-DATS composite fibres

[0160] PCL concentration, selection solvents, pressure and rotational speed were chosen based on previous studies that identified and optimal fibre formation during pressure gyration technique. Therefore, a binary solvent of chloroform / methanol (3: 1) was used to dissolve PCL and no pressure was applied (O.OmPa) through the fibre formation process (Altun et al., 2022, European Polymer Journal, 173, p. 111300).

[0161] An average diameter of 2.014 ± 0.14 pm for PCL (15 w / v%) and aligned fibres were obtained.

[0162] The addition of GO to PCL solution have showed a decrease in fibre diameter from 2.014 ± 0.14 pm to 1.106 pm. These results were endorsed by previous suspension rheology characterization which stablished that the addition of GO in PCL suspension decrease the surface tension and viscosity consequently, the centrifugal forced applied during the gyration process easily overcome the surface tension of solution leading to a smaller diameter in comparison to pure PCL. These observations have been supported by previous investigations which demonstrated that adding GO to the PCL solution decreases the viscosity, surface tension hence, a smaller fibre diameter is formed. Another study reported that the lower viscosity of solution and the lower or non-working pressure, the smaller the fibre diameter.

[0163] However, a minor increase in PCL / GO composite fibre diameter was observed when the concentration of GO was increased (1, 2 and 4 w / w%). Fibre diameter averages were denoted at 1.106 pm, 1.22 pm, and 1.51 pm, respectively. It has been hypothesized that this increase occurred due to an increase GO nanosheets agglomeration within the polymer, leading to a uniform dispersion and the formation of larger fibre diameters.

[0164] The introduction of a small concentration of Na2S-GO and DATS-GO (lw / w%) have shown a smaller diameter fibre than those observed in pure PCL as it occurs with PCL / GO due to decrease in viscosity and surface tension of the solution. However, the addition of higher concentrations of Na2S-GO and DATS-GO (2 and 4 w / w%) increased dramatically the fibre diameter in comparison with pure PCL fibre and PCL / GO at 2 and 4 w / w% due to an increase in surface tension and viscosity. This phenomenon has been referred to the loss of hydrophilic functional groups and surfactant-like behaviour of GO leading to poorer suspension dispersion in solution and higher Na2S-GO and DATS-GO agglomeration. Furthermore, a bead-on string appearance and lower formation of fibres were associated with a high surface tension which might hinder the fibre formation because it decreases the ability of the jet to maintain its integrity.

[0165] Porosity was detected in most of the fibres which were attributed to the volatility of solvent system. Chloroform (61 °C) evaporates faster than methanol and pores with elliptical shape, longer in dimension and aligned with the fibre axis were arisen. These surface pores are beneficial in exposing composite fibres to the environment, increase surface area for bacteria to interact with and work to physically trap the bacteria which is useful in antimicrobial applications.

[0166] Pure PCL (8w / w%) fibres had a diameter of 0.046 ± 0.004 pm, providing a high surface area for tissue interaction. Additionally, Na2S-GO PCL and DATS-GO PCL composite fibres at concentrations of 1, 2 and 4 w / w% exhibited higher porosity compared to PCL fibres. This increased porosity is advantageous for physically trapping bacteria and enabling a stimuli-release of H2S to the infected environment. Raman Spectroscopy

[0167] Samples were analysed by Raman spectroscopy.

[0168] Figure 3 of the accompanying drawings shows stacked Raman spectra for PCL (spun using pressurised gyration apparatus) alone, Na2S@GO, DATS@GO, GO, PCL-GO, PCL-Na2S@GO and PCL-DATS@GO composite fibres.

[0169] GO exhibited two distinct bands at 1597 (G-band) and 1357 cm1(D-band), where G- band is a distinctive feature found in the in-plane oscillation of carbon atoms connected through sp2bonding and D band is typically associated with the existence of defects in the sp2bonding.

[0170] DAT and Na2S conjugated to GO each showed an additional peak at 2472 cm ’, corresponding to sulfur groups. Furthermore, the G and D peaks of GO were broadened which shows the successful conjugation of DATS and Na2S with GO.

[0171] In pure PCL, there are additional typical Raman peaks at 916 cm1(C-COO), and others within the spectral ranges 1003-1110 cm1(skeletal stretching), 1270-1300 cm1(CFL), 1405-1470 cm1(CFL), and 2800-3200 cm1(CH) refer to the crystalline fraction.

[0172] PCL-DATS@GO and PCL-Na2S@GO showed shift in the G peak revealing that there is a shift in the vibrational bands of graphene, clearly showing that the graphene layers are in contact with the polymer. The CC vibrational peak is located at 1642 cm1in PCL-DATS@GO composite. CO directly interacts with each other when the DATS molecule binds to the PCL and GO. Hence the corresponding peaks can easily be changed because of the interaction between PCL and DATS@GO.

[0173] These results show the successful conjugation of DATS and Na2S with GO and also the fibre formation of PCL with functionalised GO.

[0174] X-ray diffraction (XRD)

[0175] XRD patterns of GO was similar to the typical sp2-hybridised carbon, representing typical peaks at 16 = 12.3°, displaying the presence of crystalline graphene structure with interlayer spacing of 9.02 A. The conjugation of GO with DATS and Na2S shows significant shift in peak at

[0176] 26 = 12.3° to 11° and 9.7° corresponding higher interlayer spacing. Interestingly, one additional peak was observed in both functionalised around 26 = 26.5°, corresponds to the high amount of defects in graphene as well as the presence of sulfide groups, thus confirming the successful conjugation of GO with DATS and Na2S.

[0177] FTIR

[0178] Fourier Transform Infrared (FTIR) spectra were recorded using a Bruker Optics Tensor-

[0179] 27 spectrometer in the wavenumber range of 4000-500 cm1. The samples were prepared by mixing the composite fibres with potassium bromide (KBr) to form pellets.

[0180] Figure 4 of the accompanying drawings shows stacked FTIR spectra of pure PCL, PCL+GO, and PCL+GO / DATS. The FTIR spectra of pure PCL showed significant characteristic peaks at 732 cm"1, 1165 cm"1, 1722 cm"1, 2866 cm"1, and 2942 cm"1. The spectra of PCL+GO composite fibres showed an absorption peak at 1047 cm"1and a significant peak near 1366 cm"1. After the introduction of DATS into the PCL+GO composites, additional absorption peaks appeared at 733 cm"1and 2980 cm"1.

[0181] The FTIR spectra of GO modified with DATS and Na2S showed the specific functional groups of C-O-C (-1000 cm ' ), C-0 (1230 cm ' ), C=C (-1620 cm ' ) and C=O (1740- 1720 cm ' ) bonds. The band in the region of 3600-3000 cm1corresponds to O-H stretching vibrations of hydroxyl and carboxyl functional groups arising from GO. These results show the successful conjugation of DATS and Na2S with GO.

[0182] Antimicrobial Effects

[0183] The antimicrobial effects of samples were quantitatively assessed using the optical density method. The antimicrobial effects were determined for: control (no sample); pure PCL (formed by electrospinning); multilayer PCL (a core of spun PCL and a sheath of electrospun PCL, formed by pressurised gyration); graphene oxide (1%, 2% and 4% in spun PCL), formed by electrospinning; layered graphene oxide “composite” (1%, 2% and 4% in PCL) in electrospun PCL, formed by pressurised gyration; Na2S (1%, 2% and 4% Na2S in spun PCL); layered Na2S “composite” (1%, 2% and 4% Na2S on GO in spun PCL) in electrospun PCL;

[0184] DATS (1%, 2% and 4% DATS in spun PCL), formed by electrospinning; and layered DATS “composite” (1%, 2% and 4% DATS on GO in spun PCL) in electrospun PCL.

[0185] Standard pathogenic bacterial strains, Staphylococcus aureus (gram-positive) and Escherichia coli (gram -negative), were cultivated at 37°C in Luria-Bertani (LB) medium while being shaken (SciQuip Benchtop Shaker, SciQuip Ltd, Newtown, Wem, Shropshire) at 300 rpm. The original broth medium, without further treatment, was used as a control group to confirm appreciable bacterial growth of up to approximately up to — 106 cfu niL This well-grown bacterium was inoculated in each pre-labelled sample vial, each containing 5 mL of microbial broth solution alongside a circular film of 15 mg of each sample. The vials were then incubated in dark at 37 °C for testing. After 12 hours, 100 pL of the medium was drawn from all the sample vials and transferred to a 96-well plate for optical density measurement using the Tecan Infinite® F50 plate reader (Tecan Trading AG, Switzerland) at 600 nm to examine the bacterial growth in different samples in comparison to the control.

[0186] Figure 5 of the accompanying drawings shows the growth inhibition of S. aureus after 12 hours of incubation with the test samples. The untreated control groups showed high optical density (OD) values, indicating that these bacteria can grow normally without any antimicrobial agent, thus providing a reliable baseline. It can be seen that, while all samples inhibited the growth of S. aureus in a concentration-dependent manner, the composites of the invention, including graphene oxide and a hydrogen sulfide releasing agent, inhibited the growth of S. aureus more than any other sample at the same concentration.

[0187] Pure PCL showed a slight antimicrobial effect in bacterial tests, with slightly lower OD values than the control. This may be attributed to the physical barrier effect of the matrix material, which hinders bacterial attachment or proliferation to some extent. However, the antibacterial effect was relatively limited due to the lack of active antibacterial components. GO exhibited dose-dependent antibacterial activity. GO has a high surface area and is rich in oxidative functional groups that can interact with bacterial cell membranes, causing physical damage and leakage of cell contents. In addition, the oxidative groups in GO may generate reactive oxygen species (ROS) that further damage the cellular structure of bacteria. These results suggest that high concentrations of GO have strong antibacterial effects on .S'. aureus, while the pressurised gyration method seems to be slightly superior to the electrospinning method in enhancing the antibacterial properties of GO. This advantage may be related to the fibrous structure produced by the pressurised gyration method, which usually has a higher specific surface area and a more homogeneous pore structure, contributing to the increased contact area between the GO and the bacterial cells, thereby enhancing the antibacterial effect. Composites containing diallyl trisulfide (DATS) showed significant antibacterial activity in bacterial tests. These antibacterial effects were greater than for GO composites without a H2S releasing agent. Composites containing DATS also exhibited a dose-dependent response.

[0188] Figure 6 of the accompanying drawings shows the growth inhibition of E. coli after 12 hours of incubation with the test samples. The untreated control groups showed high optical density (OD) values, indicating that these bacteria can grow normally without any antimicrobial agent, thus providing a reliable baseline. It can be seen that, while all samples inhibited the growth of E. coli in a concentration-dependent manner, the composites of the invention, including graphene oxide and a hydrogen sulfide releasing agent, inhibited the growth of E. coli more than any other sample at the same concentration.

[0189] Therefore, the composites of the invention exhibit antimicrobial effects that are superior compared to PCL, graphene oxide, PCL / graphene oxide composite, NaS2, or DATS alone. The composites of the invention may be considered to exhibit synergistic effects compared to the individual components thereof.

[0190] DATS is a H2S donating compound that has been shown to possess strong antibacterial activity against both Gram-positive and Gram-negative bacteria, mainly by disrupting the enzyme systems and membrane structures of bacteria. The performance of DATS was superior when formed into composite fibres using pressurised gyration (PG), compared to the antibacterial performance of composites formed by electrospinning. This may be attributed to the fact that the fibrous structure produced by PG facilitates a more homogeneous distribution and release of DATS, increasing the frequency of contact with bacterial cells and further enhancing the antimicrobial effect.

[0191] This demonstrates that the TUS-releasing composite fibres possess the ability to inhibit the growth of both Gram-positive and Gram-negative bacterial strains.

Claims

CLAIMS1. An article formed of a composition, wherein the composition comprises: a hydrogen sulfide releasing agent, a graphene-based material, and polymer, and wherein the hydrogen sulfide releasing agent and the graphene-based material are encapsulated within the polymer.

2. The article of claim 1, wherein the graphene-based material is graphene oxide, graphene and / or reduced graphene oxide.

3. The article of claim 1 or claim 2, wherein the hydrogen sulfide releasing agent is an inorganic sulfide salt and / or an organic compound comprising a group selected from the list consisting of: a sulfide, an allyl sulfide, a phosphinodithioate, a thiosulfinate, an S-aroylthiooxime, a 1, 2-dithiole-3-thione, a phosphorodithioate, a phosphonamidothioate, an N-(benzoylthio)benzamide, a perthiol, a dithioperoxyanhydride, an arylthioamide, a gem-dithiol, a ketoprofenate-cage, and a thioamino acid.

4. The article of claim 3, wherein the hydrogen sulfide releasing agent is Na2S and / or DATS.

5. The article of any preceding claim, wherein the polymer is a polyester and / or a cellulose based polymer.

6. The article of claim 5, wherein the polymer is selected from the list consisting of: polycaprolactone, poly-3 -hydroybutyrate, polylactic acid, cellulose acetate, and celluloid.

7. The article of any preceding claim, wherein the composition is present as fibres.

8. The article of any preceding claim, wherein the article comprises one or more surface layer of polymer and one or more core layer of the composition.

9. The article of any preceding claim, wherein the article is a medical device.

10. The article of claim 9, wherein the medical device is a wound dressing, a catheter, and / or an implant.1 1. The article of any preceding claim, wherein the composition comprises the hydrogen sulfide releasing agent in a proportion of 0.1 to 10 wt%.

12. The article of any preceding claim, wherein the composition comprises the graphene-based material in a proportion of from 0.1 to 10 wt%.

13. The article of any preceding claim, wherein the composition comprises the polymer in a proportion of the polymer in a proportion of from 80 to 99.8 wt%.

14. The article of any preceding claim, wherein:- the hydrogen sulfide releasing agent is an inorganic sulfide salt and / or an organic compound selected from the list consisting of: diallyl sulfide, diallyl disulfide, diallyl trisulfide, dipropyl disulfide, allyl methyl sulfide, diallyl thiosulfinate, allicin, a SATO disclosed by Org. Lett. 2014, 16, 6, 1558-1561, ATB-337, ATB-429, HS-SUL, HS-NAP, HA-ASA and HS-IBU, thioglycine, thiovaline, 2,4-bis(4-methoxyphenyl)-l,3,2,4-dithiadiphosphetane-2,4-disulfide (Lawesson’s reagent), morpholin-4-ium 4-methoxyphenyl(morpholino) phosphinodithioate, GYY4137, and JK-1 ; the graphene-based material is graphene oxide; the polymer is selected from the group consisting of polycaprolactone, poly-3- hydroybutyrate, polylactic acid, and combinations thereof; the composition comprises the hydrogen sulfide releasing agent in a proportion of 0. 1 to 10 wt%; the composition comprises graphene-based material in a proportion of from 0.1 to 10 wt%; and the composition comprises polymer in a proportion of the polymer in a proportion of from 80 to 99.8 wt%.

15. The article of any preceding claim, wherein: the hydrogen sulfide releasing agent selected from the group consisting of Na2S, diallyl trisulfide, and combinations thereof; the graphene-based material is graphene oxide; the polymer is selected from the group consisting of polycaprolactone (PCL), poly-3 -hydroybutyrate, polylactic acid, and combinations thereof; the composition comprises the hydrogen sulfide releasing agent in a proportion of 0. 1 to 10 wt%; the composition comprises graphene-based material in a proportion of from 0.1 to 10 wt%; and the composition comprises polymer in a proportion of the polymer in a proportion of from 80 to 99.8 wt%.

16. A composition comprising:- a hydrogen sulfide releasing agent,- graphene-based material, and- polymer, and wherein the hydrogen sulfide releasing agent and the graphene-based material are encapsulated within polymer.

17. A composition as defined by claim 16 for use as a medicament.

18. A composition as defined by claim 16 for use in the prevention, amelioration and / or treatment of a hydrogen sulfide-responsive disease or condition.

19. The composition for use of claim 16, wherein the hydrogen sulfide-responsive disease or condition is selected from the list consisting of: a microbial infection, myocardial infarction, hypertension, peripheral arterial disease, cardiovascular diseases, atherosclerosis, ischemia reperfusion, heart failure, peptic ulcer disease, acute and / or chronic inflammatory diseases, diabetes, diabetic kidney disease, gastric ulcers, metabolic syndrome, stroke, inflammatory bowel disease, cancer, neurological disorders / diseases, ethylmalonic encephalopathy, Parkinson's disease, Alzheimer's disease, and erectile dysfunction.

20. A pharmaceutical composition comprising the composition of the claim 16 and a pharmaceutically acceptable carrier and / or diluent.

21. A method of preparation of a fibre composite, wherein the method comprises: providing a liquid mixture (e.g. solution and / or suspension), wherein the liquid mixture comprises a polymer, graphene-based material loaded with a hydrogen sulfide releasing agent, and a solvent; and spinning the liquid mixture in a vessel, wherein the vessel comprises an orifice on the radially outermost wall, such that the liquid mixture escapes from the vessel through the orifice so as to form the fibre composite.

22. The method of claim 21, wherein the rotation of the vessel may be at a rate of 5000rpm or more.23 . A method of preventing, treating or ameliorating a microbial infection in a tissue of a subject, the method comprising contacting an article of any one of claims 1 to 15 and / or a composite of claim 16 with the tissue.

24. The method of claim 23, wherein the step of contacting the article and / or the composite with the tissue is performed by contacting the article and / or the composite with the tissue for a period of time of 1 minute or longer.

25. A method of achieving sustained release of hydrogen sulfide, the method comprising:- providing an article of any one of claims 1 to 15 and / or a composition of claim 16; and- exposing the article and / or the composition to moisture.

26. The method of claim 25, wherein the method achieves a desired concentration of hydrogen sulfide in an environment surrounding the article and / or composition.

27. Use of an article of any one of claims 1 to 15 and / or a composition of claim 16 as an antibacterial agent.

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