Patent Application
20200069777
This invention relates to antimicrobial compositions and formulations, particularly colloids, suspensions or emulsions. The compositions and formulations may be for topical application for the treatment of antimicrobial infections, such as viral, bacterial, or fungal infections.
Cold sores are small blisters that develop on the lips or around the mouth. They are caused by the herpes simplex virus (HSV) and usually clear up without treatment within 7 to 10 days. Cold sores often start with a tingling, itching or burning sensation around the mouth. Small fluid-filled sores will then appear, most commonly on the edges of the lower lip. Topical products, such as creams or gels, can be used to treat cold sores. Many are prescription medicines that may slightly shorten the duration of cold sores, usually by just 1 to 2 days.
Genital herpes is a common infection caused by the herpes simplex virus (HSV). It causes painful blisters on the genitals and the surrounding areas. Herpes can be treated with anti-viral agents. However, these can cause side effects, such as nausea and headaches.
There remains a need for topical formulations that provide effective treatment of HSV and other viral or microbial infections.
The Applicant has found that compositions that are able to release hydrogen peroxide at the site of a microbial infection are particularly effective at preventing or inhibiting the infection.
Surgihoney™ is a chemical engineered honey that has the ability to deliver variable and sustained doses of reactive oxygen species (ROS). Studies in vitro and in vivo have demonstrated Surgihoney's efficacy in eradication of infection. This has included drug resistant strains, such as methicillin-resistant S. aureus (MRSA) and vanomycin-resistant Enterococcus faecium (Dryden, M., Lockyer, G., Saeed, K., & Cooke, J. (2014). Engineered Honey: In Vitro Antimicrobial Activity of a Novel Topical Wound Care Treatment. Journal of Global Antimicrobial Resistance, 2, 168-172). It was also shown to be effective against fungi and prevented or reduced the seeding of biofilms (Dryden, M., Halstead, F., & Cooke, J. (2015). Engineered Honey to Manage Bacterial Bioburden and Biofilm in Chronic Wounds. EWMA Free Paper Session: Infection and Antimicrobials). Chemically engineered honeys, such as honey with added glucose oxidase, are disclosed in WO 2015/166197 A1.
At present, Surgihoney™ is available in a sachet form for topical administration. However, administration of Surgihoney™ in this form may be inconvenient, make application of a controlled dose difficult and may be clinically non-optimal.
According to the invention there is provided a composition for generating antimicrobial activity, which comprises: a lipophilic phase; an aqueous phase; an enzyme that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a substrate for the enzyme. A composition of the invention may be in the form of a colloid or a suspension.
The term “colloid” is used herein to refer to a homogeneous non-crystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance. Colloids include gels, sols, and emulsions. The particles do not settle, and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.
The term “suspension” is used herein to refer to a mixture in which small particles of a substance are dispersed throughout a liquid. If a suspension is left undisturbed, the particles are likely to settle to the bottom. The particles in a suspension are larger than those in either a colloid or a solution.
A composition of the invention may be in the form of an emulsion. The term “emulsion” is used herein to refer to a fine dispersion of minute droplets of one liquid in another in which it is not soluble or miscible. An emulsion of the invention may be an oil and water emulsion, in particular an oil-in-water emulsion, or a water-in-oil emulsion. The composition may be a micro-emulsion.
Compositions of the invention may comprise a first phase (or first liquid, or first component) and a second phase (or second liquid, or second component), an enzyme that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a substrate for the enzyme. The first phase and the second phase may be immiscible. For example, the first phase may be less polar than the second phase. The first phase may be a non-polar phase such as a lipophilic phase or a hydrophobic phase e.g. an oil. The second phase may be a polar phase, such as an aqueous phase. The second phase may comprise a non-aqueous solvent. Droplets or micelles of the second phase may be dispersed within the first phase.
The second phase may comprise water and/or non-aqueous solvent. The enzyme and the substance of the composition may be dissolved in the water and/or non-aqueous solvent.
It is conceivable that, in some embodiments, the second phase may not comprise water or may comprise substantially no water. In such circumstances, the second phase may be described as non-aqueous. For example, the enzyme and the substance comprising a substrate for the enzyme may be dissolved in a non-aqueous solvent. The non-aqueous solvent may be immiscible with respect to the first phase e.g. lipophilic phase.
In some embodiments, the enzyme that is able to convert a substrate to release hydrogen peroxide and the substance that includes a substrate for the enzyme may be contained within micelles dispersed within the first phase, e.g. lipophilic phase.
In some compositions, the composition may be in the form of a double emulsion. For example, droplets containing the enzyme that is able to convert a substrate to release hydrogen peroxide and the substance that includes a substrate for the enzyme may be dispersed within globules of a lipophilic phase (e.g. oil globules) and globules may be dispersed within an aqueous phase. Such a double emulsion may be termed a water-in-oil-in-water type (W/OIW) emulsion.
A composition of the invention may further comprise an emulsifying agent (or emulsifier). Emulsions can be stabilized by adsorption of surface active agents (emulsifying agents) at the emulsion interface. Emulsifying agents lower the interfacial tension to maintain the droplets in a dispersed state. An emulsifying agent has a hydrophilic part and a lipophilic part. It is possible to calculate the relative quantities of an emulsifying agent(s) necessary to produce the most physically stable emulsions for a particular formulation with water combination. This approach is called the hydrophilic-lipophilic balance (HLB) method (“The HLB SYSTEM a time-saving guide to emulsifier selection” ICI Americas Inc., Wlimington, Del. 19897, 1976, revised 1980). Each emulsifying agent is allocated an HLB number representing the relative properties of the lipophilic and hydrophilic parts of the molecule. High numbers (up to a theoretical number of 20), indicates an emulsifying agent exhibiting mainly hydrophilic or polar properties, whereas low numbers represent lipophilic or non-polar characteristics. According to the HLB System, all fats and oils have a Required HLB. Emulsions with optimal performance can be yielded by matching the HLB requirement with the emulsifying agent's HLB value. For an oil-in-water emulsion, the more polar the oil phase the more polar the emulsifying agent(s) must be. For example, to emulsify Soybean Oil, which has a Required HLB of 7, according to the HLB system, it would be necessary to use an emulsifying agent, or blend of emulsifying agents, with an HLB of 7±1. The HLB of emulsifying agents can be calculated or determined through trial and error.
Thus, the lipophilic phase of a composition of the invention may require an emulsifying agent of a particular HLB number in order to ensure a stable product. The lipophilic phase of a composition of the invention may comprise an oil or a wax. Examples of oils and waxes (by their International Nomenclature of Cosmetic Ingredients, INCI, name) for use in a lipophilic phase of a composition of the invention (with their respective Required HLBs) include the following:
Aleurites Moluccana Seed Oil [7]
Cannabis Sativa Seed Oil [7]
Daucus Carota Sativa (Carrot) Root Extract [6]
Macadamia (Ternifolia) Nut Oil [7]
Mangifera Indica (Mango) Seed Butter [8]
Oryza Sativa (Rice Bran) Oil [7]
Theobroma Cacao (Cocoa) Seed Butter [6]
In some embodiments, the lipophilic phase of a composition of the invention comprises a beeswax.
In some embodiments, the lipophilic phase is an oil. In some embodiments, the oil is selected from olive oil, corn oil, vegetable oil, sunflower oil or paraffin oil. In a preferred embodiment, the oil may be olive oil. In another preferred embodiment, the oil may be paraffin oil.
Water-in-oil emulsifying agents for use in compositions of the invention may have an HLB value in the range 3-6. Oil-in-water emulsifying agents for use in compositions of the invention may have an HLB value in the range 8-18. Examples of emulsifying agents (by their INCI name) for use in compositions of the invention (with their HLB numbers) include the following:
In some embodiments, an emulsifying agent of a composition of the invention comprises a lecithin.
Emulsifying agents include ionic or non-ionic surfactants, and lipophilic fatty amphiles (for example, fatty alcohols or fatty acids). Non-ionic surfactants may be preferred since they may be less irritating to skin that anionic or cationic surfactants.
Other examples of suitable emulsifying agents include: Surfactants: Sodium lauryl sulphate, Cetrimide, Cetomacrogol 1000, PEG 1000 monostearate, Triethanolamine stearate, Sodium stearate; Fatty amphiphiles: Cetostearyl alcohol, Cetyl alcohol, Stearyl alcohol, Glyceryl monostearate, Stearic acid, Phosphatidylcholine.
Examples of commercial emulsifying waxes include: Emulsifying wax BP (Cetostearyl alcohol, sodium lauryl sulphate), Emulsifying wax USNF (Cetyl alcohol, polysorbate), Cationic emulsifying wax BPC (Cetostearyl alcohol, cetrimide), Glyceryl monostearate S.E. (Glyceryl monostearate, sodium stearate), Cetomacrogol emulsifying wax BPC (Cetostearyl alcohol, cetomacrogol 1000), Polawax (Cetyl alcohol, non-ionic surfactant), Lecithin (Phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidic acid).
Surfactants for use in compositions of the invention may include one or more of TWEEN (e.g. TWEEN 80), SPAN (e.g. SPAN 80), Poloxamer (e.g. Poloxamer 407) and Polyglycerol polyricinoleate (PGPR). A preferred surfactant may be Poloxamer, such as Poloxamer 407. Another preferred surfactant may be PGPR.
Surfactants may include a surfactant polymer, or co-polymer. For example, a suitable surfactant may be a triblock copolymer consisting of a central hydrophobic block flanked by two hydrophilic blocks.
According to the invention, there is provided a composition for generating antimicrobial activity, which comprises: an oil; an emulsifier; an enzyme that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a substrate for the enzyme.
Compositions of the invention may comprise non-aqueous solvent. The non-aqueous solvent may be a polar solvent, such as a solvent with a dielectric constant of greater than 15. The non-aqueous solvent may be an organic solvent. For example, the solvent may be, or may comprise, glycerol, dimethylsulphoxide, propylene glycol or polyethylene glycol. The non-aqueous solvent may be immiscible with respect to the first phase e.g. the lipophilic phase (such as oil).
In a preferred embodiment, the non-aqueous solvent may be, or comprise, glycerol.
In some embodiments, compositions of the invention may comprise micelles, preferably reverse micelles. Within each micelle may be the enzyme and the substance (which may comprise an unrefined natural substance, such as honey), and outside of the micelle may be the first phase, e.g. the lipophilic phase (such as oil). Within each reverse micelle there may also be water and/or non-aqueous solvent. Within each micelle there may not be sufficient water for the enzyme to convert the substrate.
Compositions of the invention may comprise further components which may assist in reducing coalescence. Coalescence describes the situation in which two or more droplets, or micelles, combine to form a single droplet, or micelle. In order to reduce or prevent, coalescence, the strength of the interfacial film, i.e. the interface between the lipophilic phase and the aqueous phase, may be strengthened. This may be achieved, for example, by increasing the surfactant concentration, including an amphiphilic polymer, and/or by adding an alcohol, such as an aliphatic alcohol with 5-7 carbon atoms.
Compositions of the invention may be suitable for topical application, in particular topical application to a human subject. A composition for topical application may be applied to body surfaces such as skin or mucous membranes. Compositions of the invention for topical application may be in the form, for example, of a cream, a lotion, or a lip balm.
The term “cream” is used herein to refer to a semi-solid emulsion of oil-in-water, or water-in-oil, for topical use. Oil-in-water (o/w) creams are composed of small droplets of oil dispersed in a continuous aqueous phase, and water-in-oil (w/o) creams are composed of small droplets of water dispersed in a continuous oily phase. Oil-in-water creams are less greasy and more easily washed off using water. Water-in-oil creams are more moisturising as they provide an oily barrier which reduces water loss from the outermost layer of the skin.
The term “cream” may also refer to a semi-solid emulsion in which droplets of a first phase are dispersed in a continuous second phase, or in which droplets of a second phase are dispersed in a continuous first phase. For example, the first phase may be less polar than the second phase. The first phase may be a non-polar phase such as a lipophilic phase or a hydrophobic phase e.g. an oil. The second phase may be a polar phase, such as an aqueous phase. The second phase may comprise a non-aqueous solvent. The second phase may comprise water and/or non-aqueous solvent. It is conceivable that, in some embodiments, the second phase may not comprise water or may comprise substantially no water. In such circumstances, the second phase may be described as non-aqueous. The non-aqueous solvent may be immiscible with respect to the first phase e.g. lipophilic phase.
The term “lotion” is used herein to refer to a liquid suspension or emulsion for topical application. A lotion may comprise finely powdered, insoluble solids held in suspension by suspending agents and/or surface-active agents, or an emulsion (particularly, an oil-in-water emulsion) stabilized by one or more surface-active agents. A lotion has lower viscosity than a cream.
The term “lip balm” is used herein the refer to a wax-like substance applied topically to the lips of the mouth to moisturize and relieve chapped or dry lips. Lip balm may include, for example, beeswax or carnauba wax, camphor, cetyl alcohol, lanolin, paraffin, and petrolatum, among other ingredients.
Advantageously, compositions of the invention may be sprayable. For example, this may assist in overcoming some of the difficulties in applying Surgihoney in its conventional form. For example, in some circumstances, Surgihoney (which may be sticky and viscous) may be difficult to apply to an infection site. Consequently, compositions of the invention may be delivered to a patient using a spray device. The device may be a spraying or atomising device, such as a pump-action spray or an aerosol spray. The invention may thus provide a spraying device comprising a composition of the invention.
Compositions of the invention may be suitable for internal administration to a subject. For example, the composition may be suitable for administration into a subject's respiratory tract. Surgihoney, in its conventional form, may not be easily administered to a subject's respiratory tract.
Compositions of the invention may be administered to the respiratory tract using a nebuliser or an inhaler. Consequently, the invention may provide a nebuliser of inhaler comprising a composition of the invention.
A nebuliser is a device that converts liquid into aerosol droplets suitable for inhalation. Nebulisers use oxygen, compressed air or ultrasonic power to break up medication solutions and deliver a therapeutic dose of aerosol particles directly to the lungs. A wide variety of nebulisers is available. Nebulisers can be driven by compressed gas (jet nebuliser) or by an ultrasonically vibrating crystal (ultrasonic nebuliser).
In order to produce small enough particles from solution in 5-10 minutes, gas flow rates of at least 6 L/minute are usually necessary. Ultrasonic nebulisers use a rapidly vibrating piezoelectric crystal to produce aerosol particles. Ultrasonic nebuliser machines are often smaller and quieter.
Many nebulisers deliver only 10% of the prescribed drug dose to the lungs. Much of the drug is caught on the internal apparatus or wasted during exhalation. The efficiency of drug delivery depends on the type and volume of nebuliser chamber and the flow rate at which it is driven. Some chambers have reservoir and valve systems to increase efficiency of particle delivery during inspiration and reduce environmental losses during expiration. Breath-assisted open vent systems improve drug delivery but are dependent on the patient having an adequate expiratory flow. Face masks or mouthpieces may be used for administration of aerosol particles.
Nebulisers are used for the treatment of many respiratory diseases. Indications for nebuliser use include the management of exacerbations and long-term treatment of chronic obstructive pulmonary disease (COPD), management of cystic fibrosis, bronchiectasis, asthma, HIV/AIDS and symptomatic relief in palliative care.
Nebulised compositions of the invention may be used to prevent or treat a microbial infection, for example a microbial infection that comprises a biofilm, or a microbe that is capable of forming a biofilm, in a subject suffering from respiratory disease, such as COPD, cystic fibrosis, bronchiectasis, or asthma, or an HIV/AIDS-associated respiratory infection, or respiratory infection associated with terminal disease.
A composition of the invention may be used to prevent or treat a microbial infection that comprises a biofilm, or a microbe that is capable of forming a biofilm. The biofilm may comprise a biofilm-forming bacterium, fungus, or virus. The microbe that is capable of forming a biofilm may be a bacterium, fungus, or virus.
In some embodiments, a composition used to prevent or treat a microbial infection may exclude a nebulised composition of the invention.
The enzyme of a composition of the invention may be additional (i.e. added as a result of human intervention) to any enzyme activity able to convert the substrate to release hydrogen peroxide (referred to herein as “substrate conversion activity”) that may be present in the substance, i.e. the composition may comprise the substance and added enzyme. In some embodiments there may be no substrate conversion activity in the substance.
A composition of the invention may be a storage-stable composition which does not include sufficient free water to allow the enzyme to convert the substrate. Preferred compositions according to the invention do not include sufficient free water to allow the enzyme to convert the substrate.
For example, in some embodiments, the enzyme and the substance comprising a substrate for the enzyme may be encapsulated or contained within micelles (such as reverse micelles), and within the micelles there may not be sufficient free water to allow the enzyme to convert the substrate. A non-aqueous solvent, may be present in the micelles.
Alternatively, compositions of the invention may be storage stable by virtue of the enzyme that is able to convert a substrate to release hydrogen peroxide and the substance that includes a substrate for the enzyme, being separate (or compartmentalised) from water in the composition. For example, the composition may be a double emulsion. Droplets containing the enzyme and the substance (but without sufficient free water to allow the enzyme to convert the substrate) may be dispersed within globules of oil, and the globules of oil may be dispersed within an aqueous phase (e.g. water).
In the presence of sufficient water, the enzyme of the composition (e.g. storage-stable composition) is able to convert the substrate and release hydrogen peroxide. Hydrogen peroxide is known to be effective against a wide variety of different microbes. Thus, antimicrobial activity may be generated following dilution of a composition (e.g. storage-stable composition) of the invention.
If a storage-stable composition is used, this may be diluted by liquid present at the site of administration leading to release of hydrogen peroxide at the administration site.
Compositions of the invention that do not include water, or any free water, may provide particularly stable compositions of the invention, since the enzyme will not be able to convert the substrate to release hydrogen peroxide until the composition is contacted with sufficient amount of water.
Catalase is an enzyme that catalyses the decomposition of hydrogen peroxide to water and oxygen. The use of a substance that lacks catalase activity means that there is no variability in the amount of this activity between similar substances from different sources, or from different harvests from the same source. This reduces the variability in antimicrobial activity that can be generated from such substances. Alternatively, if the substance does include catalase activity, and it is not possible or desirable to inactivate the catalase activity in the substance prior to contacting the substance with the enzyme, then sufficient enzyme may be used such that the effect of catalase activity on the hydrogen peroxide that can be generated from the substance is reduced. This also reduces the variability in antimicrobial activity that can be generated from the substance. In some embodiments, the substance may lack catalase activity.
Catalase is present in many plants and animals. Catalase activity may be removed during processing or extraction of the substance, or inactivated before use of the substance in the composition. Catalase activity may be heat inactivated, for example by pasteurisation. A suitable temperature for heat inactivation of catalase activity is at least 60° C., 70° C., or 80° C., preferably for at least 2 minutes.
The term “storage-stable” is used herein to mean that the composition can be stored at ambient temperature for at least several days, suitably at least a week or at least one or two months, whilst retaining the ability to generate antimicrobial activity following dilution of the composition. The storage temperature may be below 37° C., preferably 20-25° C. Preferably compositions are stored away from exposure to light.
Hydrogen peroxide is generally unstable at ambient temperature. The lack of sufficient free water in a storage-stable composition of the invention prevents the enzyme converting the substrate to release hydrogen peroxide, and thus helps to maintain the stability of the composition for extended periods at ambient temperature. A storage-stable composition of the invention may include some water provided that there is not sufficient free water to allow the enzyme to convert the substrate. Suitable amounts of water will vary depending on the precise components of the composition. However, typically, a storage-stable composition of the invention comprises less than 20% total water content, for example, 10%-19%, water.
Hydrogen peroxide may be released for a sustained period following dilution of the composition, depending on the amount of substrate present in the composition, and the activity of the enzyme. It will be appreciated that the amount of substrate and/or the activity of enzyme in the composition may be selected to provide for release of a relatively high level of hydrogen peroxide for a short period, or for release of a lower level of hydrogen peroxide for a longer period, following dilution of the composition. Suitably the composition provides for sustained release of hydrogen peroxide for a period of at least twenty four hours, more preferably at least forty eight hours, following dilution of the composition. Suitably the composition provides for sustained release of hydrogen peroxide at a level of less than 2 mmol/litre for a period of at least twenty four hours, following dilution of the composition.
A composition of the invention may comprise sufficient enzyme and substrate to provide for sustained release of at least 0.1, 0.5, 1 or 1.5 mmol/litre hydrogen peroxide for a period of at least 24 hours, more preferably 48 hours.
In some embodiments, compositions of the invention may provide for sustained release of hydrogen peroxide at a concentration of at least 2 ppm, at least 5 ppm, at least 10 ppm, at least 20 ppm or at least 50 ppm. In preferred embodiments, the level may be at least 2 ppm. In some embodiments, the concentration may be, at the most, 500 ppm, 200 ppm, 100 ppm, 50 ppm, 20 ppm or 10 ppm. In preferred embodiments, the level may be 20 ppm or less. In even more preferred embodiments, the level may be 10 ppm or less. For example, the concentration may be 10 to 500 ppm, 20 to 200 ppm or 50 to 100 ppm, 2 to 50 ppm, 2 to 20 ppm or 5 to 10 ppm. If the composition does not comprise sufficient free water to allow the enzyme to convert the substrate (e.g. if the composition is a dry or dried composition), hydrogen peroxide production may only occur once it has been diluted by water and there is sufficient free water to allow the enzyme to convert the substrate. Addition of water may thus initiate hydrogen peroxide production. Compositions, of the invention may provide for sustained release of hydrogen peroxide for at least 1 hour, at least 12 hours, at least 24 hours, at least 2 days, or at least 4 days. Preferably, the level of hydrogen peroxide is sustained for at least 4 days. In preferred embodiments, the level of hydrogen peroxide is sustained at 10 to 500 ppm for at least 1 hour, at least 12 hours, at least 24 hours, at least 2 days, or at least 4 days. In other embodiments, the level of hydrogen peroxide is sustained at 50 to 100 ppm for at least 1 hour, at least 12 hours, at least 24 hours, at least 2 days, or at least 4 days. In other embodiments, the level of hydrogen peroxide is sustained at 2 to 50 ppm for at least 12 hours, at least 24 hours, at least 2 days, or at least 4 days. In other embodiments, the level of hydrogen peroxide is sustained at 5 to 10 ppm for at least 12 hours, at least 24 hours, at least 2 days, or at least 4 days. In some embodiments, compositions of the invention may provide for sustained release of 2 to 500 ppm hydrogen peroxide for at least 24 hours.
It will be appreciated that there should be sufficient enzyme present in a storage-stable composition of the invention to convert the substrate and form hydrogen peroxide as needed following dilution of the composition.
In view of the importance of generation of hydrogen peroxide by compositions (e.g. storage-stable compositions) of the invention in the presence of sufficient water, it will be appreciated that the compositions should not contain any added peroxidase.
In some embodiments the enzyme is a purified enzyme. The term “purified enzyme” is used herein to include an enzyme preparation in which the enzyme has been separated from at least some of the impurities originally present when the enzyme was produced. Preferably impurities that have been removed or reduced include those that would otherwise interfere with the ability of the enzyme to convert the substrate to release hydrogen peroxide.
It may not always be necessary or desirable that the purified enzyme is at a high level of purity provided that the enzyme is able to convert the substrate to release hydrogen peroxide. In some circumstances, it may be desirable to use a relatively crude enzyme preparation. Examples of suitable purity levels include at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% pure. Preferably, the enzyme is at least 90% pure. Even more preferably, the enzyme is at least 99% pure.
It is preferred, however, that the amount of any catalase that may originally have been present when the enzyme was produced has been reduced. The enzyme may have been produced by recombinant or non-recombinant means, and may be a recombinant or non-recombinant enzyme. The enzyme may be purified from a microbial source, preferably from a non-genetically modified microbe.
The level of purity of the enzyme may be selected as appropriate depending on the intended use of the composition. For example, if the composition is intended for medical use, a medical grade or medical device grade of purity should be used.
Thus, there is provided according to the invention a composition (e.g. a storage-stable composition) for generating antimicrobial activity, which comprises: a lipophilic phase; an aqueous phase; an enzyme (e.g. a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a substrate for the enzyme; wherein the composition does not include sufficient free water to allow the enzyme to convert the substrate.
According to the invention, there is provided a composition (e.g. a storage-stable composition) for generating antimicrobial activity, comprising: a first phase; a second phase; an enzyme (e.g. purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a substrate for the enzyme, wherein the first phase and the second phase are immiscible, and wherein the composition does not comprise sufficient free water to allow the enzyme to convert the substrate.
According to the invention, there is provided a composition (e.g. a storage-stable composition) for generating antimicrobial activity, which comprises: an oil; an emulsifier; an enzyme (e.g. purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a substrate for the enzyme, wherein the composition does not include sufficient free water to allow the enzyme to convert the substrate.
In some embodiments the enzyme is an oxidoreductase enzyme. Examples of oxidoreductase enzymes that can convert a substrate to release hydrogen peroxide include glucose oxidase, hexose oxidase, cholesterol oxidase, galactose oxidase, pyranose oxidase, choline oxidase, pyruvate oxidase, glycollate oxidase, and amioacid oxidase. The corresponding substrates for these oxidoreductase enzymes are D-glucose, hexose, cholesterol, D-galactose, pyranose, choline, pyruvate, glycollate and aminoacid, respectively.
A mixture of one or more oxidoreductase enzymes and one or more substrates for the oxidoreductase enzymes may be present in a composition of the invention.
The oxidoreductase enzyme may be glucose oxidase, and the substrate may be D-glucose.
The substance may be any substance that includes a substrate for the enzyme. In some embodiments the substance lacks catalase activity.
Thus, there is also provided according to the invention a composition (e.g. a storage-stable composition) for generating antimicrobial activity, which comprises: a lipophilic phase; an aqueous phase; an enzyme (e.g. a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that lacks catalase activity and that includes a substrate for the enzyme; wherein the composition does not include sufficient free water to allow the enzyme to convert the substrate.
There is also provided, according to the invention, a composition (e.g. a storage-stable composition) for generating antimicrobial activity, comprising: a first phase; a second phase; an enzyme (e.g. a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that lacks catalase activity and that includes a substrate for the enzyme, wherein the first phase and the second phase are immiscible, and wherein the composition does not comprise sufficient free water to allow the enzyme to convert the substrate.
There is also provided according to the invention a composition (e.g. a storage-stable composition) for generating antimicrobial activity, which comprises: an oil; an enzyme (e.g. a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that lacks catalase activity and that includes a substrate for the enzyme, and wherein the composition does not include sufficient free water to allow the enzyme to convert the substrate.
The substance may be an unrefined substance. The term “unrefined” is used herein to refer to substances that have not been processed into a pure form. Unrefined substances include substances that may have been concentrated, for example by drying or boiling.
The substance may include one or more substrates from a natural source (termed herein a “natural substance”). Examples of natural substances include substances from a plant source, including from sap, roots, nectar, flowers, seeds, fruit, leaves, or shoots. The substance may be an unrefined natural substance.
Suitably the substance comprises one or more of the following substrates: D-glucose, hexose, cholesterol, D-galactose, pyranose, choline, pyruvate, glycollate or amino acid.
The substance may be a sugar substance. The term “sugar substance” is used herein to mean any substance that includes one or more sugars. The term “sugar” is used herein to refer to a carbohydrate with the general formula Cm(H2O)n. Preferred sugars include monosaccharides, such as D-glucose, hexose, or D-galactose. The sugar substance may include one or more sugars from a natural source (termed herein a “natural sugar substance”). The natural sugar substance may be an unrefined natural sugar substance. The unrefined natural sugar substance may be (or be derived from) a natural sugar product. In some embodiments, the unrefined natural sugar product is a honey. In some embodiments, the honey is a honey that has been treated to remove or inactivate catalase activity.
As discussed above, the substance itself may preferably lack an enzyme activity that is able to convert the substrate to release hydrogen peroxide (referred to as “substrate conversion activity”). Absence of substrate conversion activity from the substance has the advantage that there is then no variability in the amount of this activity between similar substances from different sources, or from different harvests from the same source. This further reduces the variability in antimicrobial activity that can be generated from such substances. Substrate conversion activity is then provided only by the enzyme that is contacted with the substance, and so the amount of substrate conversion activity present in the composition can be controlled.
Substrate conversion activity may be removed during processing or extraction of the substance, or inactivated before use of the substance in a composition of the invention. Substrate conversion activity may be inactivated by heat inactivation, for example by pasteurisation. A suitable temperature for heat inactivation of substrate conversion activity is at least 80° C., preferably for at least two minutes. An advantage of heat inactivation is that both catalase activity and substrate conversion activity can be inactivated in a single heat inactivation step.
In some embodiments of the invention, the substance is a processed, extracted, or refined substance (i.e. a substance in which impurities or unwanted elements have been removed by processing). Preferably impurities that have been removed or reduced include those that would otherwise interfere with the ability of the enzyme to convert the substrate to release hydrogen peroxide.
In some embodiments of the invention, the substance comprises a purified substrate for the enzyme. The term “purified substrate” is used herein to include a substrate preparation in which the substrate has been separated from at least some of the impurities originally present when the substrate was obtained or produced. The purified substrate may be obtained from a natural source or may be synthetically produced. The purified substrate may be a processed, extracted, or refined substrate (i.e. a substrate in which impurities or unwanted elements have been removed by processing).
It may not always be necessary or desirable that the purified substrate is at a high level of purity provided that the enzyme is able to convert the substrate to release hydrogen peroxide. In some circumstances, it may be desirable to use a relatively crude substrate preparation.
Examples of suitable purity levels include at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 99% pure. However, in some embodiments, it may be desirable that the purified substrate is a medical grade, medical device grade, or pharmaceutical grade substrate.
In particular embodiments, the purified substrate is or comprises a purified sugar substance. The purified sugar substance may be obtained from a natural source (for example a processed, extracted, or refined natural sugar substance), or be synthetically produced. The purified sugar substance may be at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 99% pure. Preferably, the purified sugar substance is at least 90% pure. Even more preferably, the purified sugar is at least 99% pure. The purified sugar substance may be a medical grade, medical device grade, or pharmaceutical grade sugar substance. The purified sugar substance may include one or more purified sugar substances, for example purified D-glucose, hexose, or D-galactose. For example the purified sugar substance may be medical grade, medical device grade, or pharmaceutical grade D-glucose, hexose, or D-galactose.
There is also provided according to the invention a composition for generating anti-microbial activity, wherein the composition comprises: a lipophilic phase; an aqueous phase; an enzyme (preferably a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a purified substrate for the enzyme.
There is also provided, according to the invention, a composition for generating antimicrobial activity, comprising: a first phase; a second phase; an enzyme (preferably a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a purified substrate for the enzyme, wherein the first phase and the second phase are immiscible.
There is also provided according to the invention a composition for generating anti-microbial activity, wherein the composition comprises: an oil; an enzyme (preferably a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a purified substrate for the enzyme.
The composition may be a storage-stable composition for generating antimicrobial activity, which comprises: a lipophilic phase; an aqueous phase; an enzyme (preferably a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a purified substrate for the enzyme; wherein the composition does not include sufficient free water to allow the enzyme to convert the substrate.
The composition may be a storage-stable composition for generating antimicrobial activity, comprising: a first phase; a second phase; an enzyme (preferably a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a purified substrate for the enzyme, wherein the first phase and the second phase are immiscible, and wherein the composition does not comprise sufficient free water to allow the enzyme to convert the substrate.
The composition may be a storage-stable composition for generating antimicrobial activity, which comprises: an oil; an enzyme (preferably a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a purified substrate for the enzyme, and wherein the composition does not include sufficient free water to allow the enzyme to convert the substrate.
The composition may be a storage-stable composition for generating antimicrobial activity, which comprises: a lipophilic phase; an aqueous phase; an enzyme (preferably a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that lacks catalase activity and that includes a purified substrate for the enzyme; wherein the composition does not include sufficient free water to allow the enzyme to convert the substrate.
The composition may be a storage-stable composition for generating antimicrobial activity, comprising: a first phase; a second phase; an enzyme (preferably a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that lacks catalase activity and that includes a substrate for the enzyme, wherein the first phase and the second phase are immiscible, and wherein the composition does not include sufficient free water to allow the enzyme to convert the substrate.
The composition may be a storage-stable composition for generating antimicrobial activity, which comprises: an oil; an enzyme (preferably a purified enzyme) that is able to convert a substrate to release hydrogen peroxide; and a substance that lacks catalase activity and that includes a purified substrate for the enzyme; wherein the composition does not include sufficient free water to allow the enzyme to convert the substrate.
In particular embodiments, the enzyme and the substrate are purified, for example purified glucose oxidase and purified D-glucose, suitably medical grade, medical device grade, or pharmaceutical grade glucose oxidase and D-glucose.
The ratio of the lipophilic phase to the aqueous phase, or the ratio of the first phase to the second phase, in a composition of the invention may be from 9:1 to 1:9, 8:1 to 1:8, 7:1 to 1:7, 6:1 to 1:6, 5:1 to 1:5, 4:1 to 1:4, 3:1 to 1:3, or 2:1 to 1:2 (v/v), for example from 4:1 to 1:4.
A composition of the invention may comprise 5-95%, 10-95%, 15-95%, 20-95%, 25-95%, 30-95%, 35-95%, 40-95%, 45-95%, 50-95%, 55-95%, 60-95%, 65-95%, 70-95%, 75-95%, 80-95%, 85-95%, or 90-95% (v/v) lipophilic phase, or first phase (including any emulsifying agent present).
Alternatively, a composition of the invention may comprise 5-95%, 5-90%, 5-85%, 5-80%, 5-75%, 5-70%, 5-65%, 5-60%, 5-55%, 5-50%, 5-45%, 5-40%, 5-35%, 5-30%, 5-25%, 5-20%, 5-15%, or 5-10% (v/v) lipophilic phase, or first phase (including any emulsifying agent present).
A composition of the invention may comprise 5-95%, 10-95%, 15-95%, 20-95%, 25-95%, 30-95%, 35-95%, 40-95%, 45-95%, 50-95%, 55-95%, 60-95%, 65-95%, 70-95%, 75-95%, 80-95%, 85-95%, or 90-95% (v/v) aqueous phase, or second phase.
Alternatively, a composition of the invention may comprise 5-95%, 5-90%, 5-85%, 5-80%, 5-75%, 5-70%, 5-65%, 5-60%, 5-55%, 5-50%, 5-45%, 5-40%, 5-35%, 5-30%, 5-25%, 5-20%, 5-15%, or 5-10% (v/v) aqueous phase, or second phase.
A composition of the invention may comprise 1-60%, 1-50%, 1-40%, 1-30%, 1-20%, or 1-10% (w/v) of the substance, for example a honey.
A composition of the invention may comprise 1-60%, 5-60%, 10-60%, 15-60%, 20-60%, 25-60%, 30-60%, 35-60%, 40-60%, 45-60%, or 50-60% (w/v) of the substance, for example a honey.
A composition of the invention may comprise 1-1500 units, 15-1500 units, 30-1500 units, 50-1500 units, 100-1500 units, 1-<685 units, 15-<685 units, 30-<685 units, 50-<685 units, 100-<685 units, 500-1000 units, 685-1000 units, or 100-500 units, of the enzyme, preferably glucose oxidase, per gram of the composition.
A composition of the invention may comprise no more than 85% (w/w) water, for example no more than 80%, 70%, 60%, 50%, 40%, 30%, or 20% (w/w) water, or less than 20% (w/w) water, for example 10-19% (w/w) water. A composition of the invention may comprise less than 20% (w/w). A composition of the invention may comprise less than 15% (w/w) water. A composition of the invention may comprise less than 12% (w/w) water. Compositions may comprise no more than 40% water, for example 10 to 40% (w/w) water. Compositions may comprise no more than 30% water, for example 20-30% (w/w) water.
A composition of the invention may comprise 10-60% (w/w) of non-aqueous solvent. In some embodiments, a composition of the invention may comprise 20-50% (w/w) of a non-aqueous solvent. In some embodiments, a composition of the invention may comprise 35-40% (w/w) of a non-aqueous solvent.
A composition of the invention may comprise 10-40% (w/w) of the first phase, e.g. lipophilic phase (such as oil). The composition may comprise 20-30% (w/w) of the first phase, e.g. lipophilic phase (such as oil).
A composition of the invention may comprise 1-10% (w/w) emulsifier. The composition may comprise 1-5% (w/w) emulsifier. The emulsifier is preferably a surfactant.
A composition of the invention may comprise 10-50% (w/w) of the substance which comprises a substrate for the enzyme. The composition may comprise 20-40% (w/w) of the substance. In some embodiments, the composition may comprise 25 to 35% (w/w) of the substance.
A composition of the invention may comprise 20-50% (w/w) of non-aqueous solvent, 20-30% (w/w) of the first phase e.g. lipophilic phase (such as oil), 1-5% (w/w) emulsifier and 20-40% (w/w) of the substance which comprises a substrate for the enzyme.
A composition of the invention may comprise 10-60% (w/w) of non-aqueous solvent, 10-40% (w/w) of the first phase e.g. lipophilic phase (such as oil), 1-10% (w/w) emulsifier and 10-50% (w/w) of the substance which comprises a substrate for the enzyme.
A composition of the invention may comprise 35-45% (w/w) of non-aqueous solvent, 20-30% (w/w) of the first phase e.g. lipophilic phase (such as oil), 1-5% (w/w) emulsifier and 25-35% (w/w) of the substance which comprises a substrate for the enzyme.
A composition of the invention may comprise 30-60% (v/v) solvent, such as a non-aqueous, polar solvent.
A composition of the invention may comprise 30-60% (v/v) first phase, such as a lipophilic phase (e.g. oil),
A composition of the invention may comprise 1-10% (v/v) emulsifier such e.g. surfactant. In some embodiments, compositions of the invention may comprise 1-5% (v/v) emulsifier.
A composition of the invention may comprise 30-70% or 40-60% (w/w) of the substance that comprises a substrate for the enzyme, for example honey.
The ratio of the first phase to the second phase in a composition of the invention may be ≤1 (v/v), for example 0.1-1:1 (v/v). In some embodiments, the ratio of the first phase to the second phase is <0.6:1 (v/v), for example 0.1-<0.6:1 (v/v). In some embodiments, the ratio of the first phase to the second phase is 0.4:1 (v/v), for example 0.1-0.4:1 (v/v).
The first phase in a composition of the invention may be present at less than 60% (v/v) of the composition. In some embodiments, the first phase is present at 10% to less than 60% (v/v) of the composition. In some embodiments, the first phase is present at 10% to less than 50% (v/v) of the composition. In some embodiments, the first phase is present at 10% to less than 40% (v/v) of the composition. In some embodiments, the first phase is present at 10% to less than 30% (v/v) of the composition. In some embodiments, the first phase is present at 10% to less than 25% (v/v) of the composition.
A composition of the invention may comprise an emulsifier. In some embodiments, the emulsifier is present at up to 25% (v/v) of the composition, for example 1-25% (v/v) of the composition, 5-25% (v/v) of the composition, or 10-25% (v/v) of the composition. In some embodiments, a composition of the invention may comprise 1-5% (v/v) of emulsifier.
The ratio of the amount of the substance that includes a substrate for the enzyme to the volume of the second phase in a composition of the invention may be from 0.5:1 to 2:1, for example 1:1.
The amount of the substance that includes a substrate for the enzyme in a composition of the invention may be up to 70% (w/v) of the composition, for example 5-70% (w/v), 10-70% (w/v), 20-70% (w/v), or 30-70% (w/v), or up to 60% (w/v) of the composition, for example 5-60% (w/v), 10-60% (w/v), 20-60% (w/v), or 30-60% (w/v), of the composition.
A composition of the invention may be an emulsion. In particular embodiments, a composition of the invention is an emulsion that comprises reverse micelles. The reverse micelles may be formed by the second phase.
In some embodiments of a composition of the invention, the enzyme and the substance that includes a substrate for the enzyme is dissolved in the second phase.
In particular embodiments of the invention, the first phase is, or comprises paraffin oil.
In particular embodiments of the invention, the second phase is, or comprises glycerol.
In particular embodiments of the invention, the emulsifier is, or comprises Polyglycerol polyricinoleate (PGPR).
In particular embodiments of the invention, the enzyme that is able to convert a substrate to release hydrogen peroxide is, or comprises purified glucose oxidase, and the substance that includes a substrate for the enzyme is, or comprises honey.
In other particular embodiments of the invention, the enzyme that is able to convert a substrate to release hydrogen peroxide is, or comprises purified glucose oxidase, and the substance that includes a substrate for the enzyme is, or comprises purified glucose.
In some embodiments of the invention, it may be advantageous to include water that is additional to any water which may be present in the substance which includes a substrate for the enzyme. For example, if compositions comprise an unrefined natural substance such as honey, the honey may already include an amount of water, although there may not be enough free water to allow the enzyme to convert the substrate to produce hydrogen peroxide.
Adding further water to the composition may allow the viscosity of the composition to be controlled, for example by reducing the viscosity of the composition. This may be particularly advantageous if it is desired to provide a sprayable composition. However, although additional water may be added, it does not necessarily mean that the composition would contain sufficient free water to allow the enzyme to convert the substrate. For instance, the composition may comprise a component that is able to bind free water, such as a non-aqueous solvent, e.g. glycerol. 1.7 g of glycerol is needed to bind 1 g of water. Other components (e.g. other non-aqueous solvents or humectants) that can bind free water, such that at least 5 g of the component binds 1 g of water, such that at least 3 g of the component binds 1 g of water, or such that at least 2 g of the component binds 1 g of water, may be used. A component that binds more free water may be preferable.
In some embodiments, compositions of the invention may not comprise glycerol, dimethyl sulphoxide, propylene glycol or polyethylene glycol. Compositions of the invention may not comprise glycerol.
Compositions of the invention may have a viscosity of 0.3 Pa·s or less, preferably 0.2 Pa·s or less, at 20° C. and at a shear rate of 100 1/s. Compositions of the invention may have a viscosity of 0.2 Pa·s or less, preferably 0.15 or less, at 20° C. and at a shear rate of 100 1/s
According to the invention, there is provided a composition for generating antimicrobial activity, comprising: a first phase (or first liquid, or first component); a second phase (or second liquid, or second component); an enzyme that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a substrate for the enzyme, wherein the first phase (or first liquid, or first component) and the second phase (or second liquid, or second component) are immiscible, and wherein the composition comprises water that is additional to any water that may be present in the substance (which may be termed “additional water”). The first phase (or first liquid, or first component) may be any as already described herein, although it preferably is, or comprises, an oil and more preferably paraffin oil. The second phase (or second liquid, or second component) may be any as already described herein, although it preferably is, or comprises, a non-aqueous solvent, more preferably glycerol.
Compositions of the invention which comprise additional water preferably also comprise an emulsifier, more preferably polyglycerol polyricinoleate.
According to the invention, there is provided a composition for generating antimicrobial activity, comprising an oil, an emulsifier, an enzyme that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a substrate for the enzyme, wherein the composition comprises water that is additional to any water that may be present in the substance.
Compositions of the invention which comprise additional water preferably do not include sufficient free water for the enzyme to convert the substrate.
Compositions of the invention may comprise 10 to 30% (v/v) non-aqueous solvent.
Compositions of the invention may comprise 15 to 25% (v/v) non-aqueous solvent.
Compositions of the invention may comprise 30 to 50% (v/v) oil. Compositions of the invention may comprise 35 to 45% (v/v) oil.
Compositions of the invention may comprise 5 to 25% (v/v) emulsifier. Compositions of the invention may comprise 10 to 20% (v/v) emulsifier.
Compositions of the invention may comprise 5 to 25% (v/v) of substance that comprises a substrate for the enzyme. Compositions of the invention may comprise 10 to 20% (v/v) of substance that comprises a substrate for the enzyme.
Compositions of the invention may comprise 1 to 15% (v/v) additional water. Compositions of the invention may comprise 1 to 10% (v/v) additional water.
Compositions of the invention that comprise additional water preferably comprise greater than 15%, or greater than 20% (w/w) water, in total. This amount of water may be provided by, for example, water that is already present in the substance that comprises a substrate for the enzyme (e.g. water that is already present in Surgihoney) and the additional water added to the composition. The total amount of water in compositions of the invention that comprise additional water may be 40% (w/w) or less, or 30% (w/w) or less. So, the total amount of water may be 15-40% (w/w), preferably 20-30% (w/w).
Compositions of the invention may comprise 10 to 30% (v/v) non-aqueous solvent, 30 to 50% (v/v) oil, 5 to 25% (v/v) emulsifier, 5 to 25% (v/v) of substance that comprises a substrate for the enzyme and, optionally 1 to 15% (v/v) additional water.
Compositions of the invention may comprise 15 to 25% (v/v) non-aqueous solvent, 35 to 45% (v/v) oil, 10 to 20% (v/v) emulsifier, 10 to 20% (v/v) of substance that comprises a substrate for the enzyme, and optionally 1 to 10% (v/v) additional water.
For example, in one embodiment, the composition may comprise 20.83% (v/v) substance (e.g. honey, such as Surgihoney), 20.83% (v/v) non-aqueous solvent (e.g. glycerol), 41.67% (v/v) oil (e.g. paraffin oil) and 16.67% (v/v) emulsifier (e.g. polyglycerol polyricinoleate). For example, in another embodiment, the composition may comprise 16.67% (v/v) substance (e.g. honey, such as Surgihoney), 20.83% (v/v) non-aqueous solvent (e.g. glycerol), 41.67% (v/v) oil (e.g. paraffin oil), 16.67% (v/v) emulsifier (e.g. polyglycerol polyricinoleate) and 4.17% (v/v) additional water.
For example, in another embodiment, the composition may comprise 12.5% (v/v) substance (e.g. honey, such as Surgihoney), 20.83% (v/v) non-aqueous solvent (e.g. glycerol), 41.67% (v/v) oil (e.g. paraffin oil), 16.67% (v/v) emulsifier (e.g. polyglycerol polyricinoleate) and 8.33% (v/v) additional water.
Compositions of the invention may comprise an additional component which is preferably a solute. References herein to “solute” may refer to one or more solute. For example, in some embodiments, compositions of the invention may comprise a plurality of solutes. In some embodiments, the composition may comprise only one solute. Preferably the solute is soluble in water.
The solute may be distinct from the substrate, or in some examples, the substrate may be same as the solute. For example, the composition may comprise fructose and fructose oxidase: the fructose being both the solute and the substrate for enzyme. In another example, the substrate may be glucose and the solute may be fructose.
The solute is preferably purified, meaning that the solute has been separated from at least some of the impurities originally present when the solute was obtained or produced. The purified solute may be obtained from a natural source or may be synthetically produced. The purified solute may be a processed, extracted, or refined substrate (i.e. a solute in which impurities or unwanted elements have been removed by processing).
It may not always be necessary or desirable that the purified solute is at a high level of purity. In some circumstances, it may be desirable to use a relatively crude solute preparation. Examples of suitable purity levels include at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 99% pure. Preferably, the purity level is at least 90%. Even more preferably, the purity level is at least 99%. However, in some embodiments, it may be desirable that the purified solute is a medical grade, medical device grade, or pharmaceutical grade solute.
The solute may be a carbohydrate. The solute may be a polysaccharide. Preferably, the solute is a sugar or sugar derivative. More preferably, the solute is a sugar. Suitable sugars include oligosaccharides, disaccharides or monosaccharides. Preferably, the sugar is a disaccharide or a monosaccharide. In particularly preferred embodiments, the sugar is a monosaccharide. Suitable sugars may include fructose, glucose, galactose, sucrose, maltose. In a particularly preferred embodiment, the sugar is fructose.
The term “sugar derivative” is used herein to refer to a sugar that has been modified by addition of one or more substituents other than a hydroxyl group. Sugar derivatives, thus encompass amino sugars, acidic sugars, deoxy sugars, sugar alcohols, glycosylamines and sugar phosphates. For example, sugar derivatives may include glucose-6-phosphateglucosamine, glucoronate, gluconate, galactosamine, glucosamine, sialic acid, deoxyribosefucose, rhamnose glucuronic acid, polyols (e.g. sorbitol, erythritol, xylitol, mannitol, lactitol and maltitol) and sucralose.
Compositions of the invention may comprise two or more solutes, as described herein. For example, compositions of the invention may comprise two or more sugars or sugar derivatives.
The composition may comprise a maximum of two solutes, e.g. two sugars or sugar derivatives; or a maximum of three solutes, e.g. three sugars or sugar derivatives.
For instance, a composition of the invention may comprise glucose, fructose and sucrose.
The solute preferably has a high solubility in water, for example a solubility which is greater than glucose. Glucose has a solubility of 90 g/100 g water at 20° C. and 1 atm. In a preferred embodiment, the solute has a solubility greater than or equal to 100 g/100 g water at 20° C. and 1 atm, in a more preferred embodiment, the solute has a solubility greater than or equal to 200 g/100 g water at 20° C. and 1 atm, in an even more preferred embodiment, the solute has a solubility greater than 300 g/100 g water at 20° C. and 1 atm.
Compositions of the invention may comprises at least two sugars or sugar derivatives (e.g. including glucose and fructose). The composition may comprise a maximum of two sugars or sugar derivatives (e.g. only glucose and fructose).
So, in some embodiments, rather than the substance being an unrefined natural substance, the substance may be a synthetic substance, such as a synthetic sugar substance. For example, the substance that comprises a substrate for the enzyme may comprise a purified substrate for the enzyme, as described herein, e.g. a purified sugar (such as glucose). The substance may also comprise one or more further purified solutes as described herein, e.g. a sugar or sugar derivative with a solubility at least 100 g/100 g water at 20° C. and 1 atm, at least 200 g/100 g water at 20° C. and 1 atm or at least 300 g/100 g water at 20° C. and 1 atm (such as fructose).
The synthetic substance may comprise at least 70%, by weight, of substrate and solute, more preferably at least 75%, by weight, of substrate and solute, and even more preferably, at least 80% by weight of substrate and solute. For example, in a preferred embodiment, the synthetic substance comprises glucose and fructose. Preferably, the glucose and fructose is present in a total amount of at least 80%, by weight.
The synthetic substance may comprise a solute (e.g. sugar or sugar derivative) in an amount of at least 40%, preferably at least 50%, by weight.
The synthetic substance may comprise a purified substrate (e.g. glucose) in an amount of at least 20% by weight, preferably at least 25% by weight, more preferably at least 30% by weight.
So, in one example of a synthetic substance, a solute (e.g. fructose) is present in an amount of 40 to 60% by weight and a substrate (e.g. glucose) is present in an amount of 20 to 40% by weight. In another example, a substrate (e.g. glucose) is present in an amount of 25 to 35% by weight and a solute (e.g. fructose) is present in an amount of 45 to 55%, by weight.
The synthetic substance may comprise at least 70% by weight sugar or sugar derivative, more preferably at least 75% by weight sugar or sugar derivative, or most preferably at least 80% by weight sugar or sugar derivative.
Preferably, the synthetic substance comprises at least two sugars or sugar derivatives (e.g. including glucose and fructose). The composition may comprise a maximum of two sugars or sugar derivatives (e.g. only glucose and fructose).
The synthetic substance may comprise water in an amount which is less than 20% by weight, but preferably greater than 10% by weight, more preferably greater than 15%, by weight. For example, water may be present in an amount of 10 to 20%, by weight. If the synthetic substance comprises water, compositions of the invention may thus comprise water that is additional to that found in the synthetic substance.
Compositions of the invention may comprise a buffer. For example, the synthetic substance may comprise the buffer. An example of a suitable buffer is a citric acid/NaOH buffer, such as a 50 mMol citric acid/Na OH buffer. Compositions of the invention may be buffered at a pH of 5 or less, e.g. 3 to 5 (such as about pH 4). Alternatively, compositions of the invention may be buffered at a pH greater than 5, e.g. 6 to 8 (such as about pH 7).
The synthetic substance may have a viscosity, such as a dynamic viscosity, of at least 5000 mPas at 20° C., more preferably at least 7500 at 20° C. Compositions of the invention may have a viscosity of 5000 to 20000 mPas at 20° C., more preferably 7500 to 12000 mPas at 20° C. A viscous solution or liquid may be afforded by high concentrations of sugars or sugar derivatives and may provide a similar viscosity to honey. A high viscosity may be beneficial in allowing a composition to remain in contact with a wound. Alternatively, a viscous solution or liquid may be afforded by the presence of, for example, non-aqueous solvents, polymers or hydrocolloid gelling agents as described herein.
The synthetic substance may comprise at least 90% by dry weight of the substrate and the solute, combined. The synthetic substance may comprise at least 95% by dry weight of the substrate and the solute, combined.
The synthetic substance may comprise at least 90% dry weight of sugar or sugar derivative. The synthetic substance may comprise at least 95% by dry weight of sugar or sugar derivative.
The synthetic substance may comprise may comprise at least 60%, dry weight of the solute (e.g. a sugar or sugar derivative). The substrate may be at least 30%, dry weight of the composition.
Compositions of the invention may not comprise an unrefined substance.
Compositions of the invention may do not include one or more substrates from a natural source (termed herein a “natural substance”). Examples of natural substances include substances from a plant source, including from sap, roots, nectar, flowers, seeds, fruit, leaves, or shoots.
Compositions of the invention may not comprise an unrefined natural substance. For example, compositions of the invention may not comprise honey.
Instead of, or in addition to, a substance comprising a substrate for the enzyme, compositions of the invention may comprise a precursor-substrate that can be converted to a substrate for the enzyme. The precursor substrate is preferably purified.
So, according to the invention, there is provided a composition for generating antimicrobial activity, comprising: a first phase (or first liquid, or first component); a second phase (or second liquid, or second component); an enzyme that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a precursor-substrate that can be converted to a substrate for the enzyme, wherein the first phase (or first liquid, or first component) and the second phase (or second liquid, or second component) are immiscible.
According to the invention, there is provided a composition for generating antimicrobial activity, comprising an oil, an emulsifier, an enzyme that is able to convert a substrate to release hydrogen peroxide; and a substance that includes a precursor-substrate that can be converted to a substrate for the enzyme.
Compositions of the invention that comprise a precursor substrate may have any of the components or characteristics as described herein. For example, the compositions may comprise water that is additional to any water that may be present in the substance. The compositions may not comprise sufficient free water to allow the precursor-substrate to be converted to the substrate, or to allow the enzyme to convert the substrate.
References herein to “precursor-substrate” may refer to one or more precursor substrate. For example, in some embodiments, compositions of the invention may comprise a plurality of precursor-substrates. In some embodiments, compositions of the invention may comprise only one precursor-substrate.
The substance preferably comprises a purified precursor-substrate. “Purified precursor-substrate” is used herein to include precursor-substrate preparation in which the precursor-substrate has been separated from at least some of the impurities originally present when the precursor-substrate was obtained or produced. The purified precursor-substrate may be obtained from a natural source or may be synthetically produced. The purified precursor-substrate may be a processed, extracted, or refined precursor-substrate (i.e. a precursor-substrate in which impurities or unwanted elements have been removed by processing).
It may not always be necessary or desirable that the precursor-substrate is at a high level of purity provided that the enzyme is able to convert the substrate to release hydrogen peroxide. In some circumstances, it may be desirable to use a relatively crude precursor-substrate preparation. Examples of suitable purity levels include at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 99% pure. Preferably, the purity level is at least 90%. Even more preferably, the purity level is at least 99% pure. However, in some embodiments, it may be desirable that the purified precursor-substrate is a medical grade, medical device grade, or pharmaceutical grade substrate.
In particular embodiments, the precursor-substrate is a purified sugar. The purified sugar may be obtained from a natural source (for example a processed, extracted, or refined natural sugar substance), or be synthetically produced. The purified sugar may be at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 99% pure. Preferably, the purity level is at least 90%. The purified sugar may be a medical grade, medical device grade, or pharmaceutical grade sugar.
For compositions of the invention which comprise a precursor-substrate, the composition preferably comprises one or more purified enzymes for converting the precursor-substrate to the substrate for the enzyme. However, in some embodiments, the precursor-substrate may not necessarily be converted to the substrate enzymatically. For example, for some precursor substrates, addition of water may be enough for conversion. Alternatively or additionally, compositions of the invention may comprise non-enzymatic catalysts.
So, compositions of the invention which comprise a precursor-substrate may comprise a first enzyme that is able to convert the substrate to release hydrogen peroxide, and a second enzyme that is able to convert the precursor-substrate to the substrate for the first enzyme.
The precursor-substrate is preferably a carbohydrate, such as a polysaccharide, or a sugar e.g. a disaccharide, or sugar derivative,
For example, the precursor-substrate may be sucrose, the first enzyme may be glucose oxidase and the second enzyme may be invertase.
In another example, the precursor-substrate may be maltose, the first enzyme may be glucose oxidase and the second enzyme may be maltase.
Compositions of the invention which comprise a precursor-substrate may comprise an enzyme (preferably a purified enzyme) that is able to convert the substrate to release hydrogen peroxide, and at least two enzymes (e.g. second and third enzymes, preferably purified enzymes) that are able to convert the precursor-substrate to the substrate for the first enzyme.
For example, the precursor-substrate may be starch, the first enzyme may be glucose oxidase and the second and third enzymes may be amylase and maltase.
For example, the precursor-substrate may be cellulose, the first enzyme may be glucose oxidase and the second and third enzymes may be cellulose and beta-glucosidase.
In some embodiments, compositions of the invention may comprise both a substrate that can be converted by the enzyme to generate hydrogen peroxide, and a precursor-substrate that can be converted to the substrate.
In preferred embodiments, compositions of the invention contain essentially no zinc oxide or comprise substantially no zinc oxide.
According to the invention, there is provided a method of making a composition of the invention, comprising mixing a first component, a second component, an enzyme that is able to convert a substrate to release hydrogen peroxide, a substance that includes a substrate for the enzyme, and water that is additional to any water that may be present in the substance, to form the composition, wherein the first component and second component are immiscible. Preferably, the first component is, or comprises, an oil and the second component is, or comprises, a non-aqueous solvent. The method may further comprise mixing an emulsifier.
The method may comprise the steps of: a) adding the water to the second component; b) mixing the second component and the additional water; c) adding the enzyme and the substance to the mixture from step b); d) mixing the enzyme and the substance with the mixture of step b); e) adding the emulsifier to the mixture from step d); and f) mixing the emulsifier with the mixture from step d). Steps b), d) and f) may be carried out at a shear rate of 1000 1/s to 4000 1/s, preferably 2500 1/s to 3500 1/s. Steps b), d) and f) may be carried out at 35 to 45° C., preferably about 40° C. The mixing in steps b) and d) may be carried out for at least a minute, preferably at least 2 minutes. The mixing in step f) may be carried out for at least 5 minutes, preferably at least 10 minutes.
In some embodiments, a composition of the invention is a cream. Typically, the viscosity of an emulsion used as a cream will be higher than that of an emulsion used as a spray. A cream may be formed by including a viscosity-increasing agent, such as a thickener or gelling agent (for example a hydrocolloid) in the composition.
Hydrocolloids are a heterogeneous group of hydrophilic, long-chain polymers (polysaccharides or proteins) characterised by their ability to form viscous dispersions and/or gels when dispersed in water (Saha and Bhattacharya, J Food Sci Technol, 2010, 47(6):587-597). The extent of thickening varies with the type and nature of the hydrocolloid. Some provide low viscosities at a fairly high concentration, but most provide a high viscosity at a concentration below 1%. The viscosity of hydrocolloid dispersions arises predominantly from non-specific entanglement of conformationally disordered polymer chains. Hydrocolloids that can be used as thickening agents (referred to herein as hydrocolloid thickeners) include starch, modified starch, xanthan, galactomannans (such as guar gum, locust bean gum, and tara gum), gum Arabic or acacia gum, gum karaya, gum tragacanth, konjac maanan, and cellulose derivatives such as carboxymethyl cellulose, methyl cellulose, and hydroxypropylmethyl cellulose.
Some hydrocolloids are able to form gels, consisting of polymer molecules cross-linked to form an interconnected molecular network immersed in a liquid medium. A rheological definition of a gel is a viscoelastic system with a ‘storage modulus’ (G′) larger than the ‘loss modulus’ (G″) (de Vries 2004, Gums and stabilizers for the food industry, vol 12. RSC Publ, Oxford, pp 22-30).
Hydrocolloids form gels by physical association of their polymer chains through hydrogen bonding, hydrophobic association, and cation-mediated cross-linking. Gelling-type hydrocolloids (or hydrocolloid gelling agents) include alginate, pectin, carrageenan, gelatin, gellan, agar, modified starch, methyl cellulose and hydroxypropylmethyl cellulose.
Gelation of hydrocolloids can occur by different mechanisms: ionotropic gelation, cold-set gelation and heat-set gelation (Burey et al. 2008, Crit Rev Food Sci Nutr 48:361-377). Ionotropic gelation occurs via cross-linking of hydrocolloid chains with ions, typically a cation-mediated gelation process of negatively-charged polysaccharides. Examples of hydrocolloids that can form gels by ionotropic gelation include alginate, carrageenan and pectin. Ionotropic gelation can be carried out by either diffusion setting or internal gelation. In cold-set gelation, hydrocolloid powders are dissolved in warm/boiling water to form a dispersion which forms a gel on cooling. Agar and gelatin form gels by this mechanism. Heat-set gels require the application of heat to gel (for example, curdlan, konjac glucomannan, methyl cellulose, starch and globular proteins).
Thus, in some embodiments, a composition of the invention comprises a viscosity-increasing agent, such as a thickener or gelling agent, for example a hydrocolloid. In particular embodiments, the hydrocolloid is, or comprises, a polysaccharide or a protein. The hydrocolloid may be a hydrocolloid thickener, such as starch, modified starch, xanthan, a galactomannan (such as guar gum, locust bean gum, and tara gum), gum Arabic or acacia gum, gum karaya, gum tragacanth, konjac maanan, or a cellulose derivative, such as carboxymethyl cellulose, methyl cellulose, or hydroxypropylmethyl cellulose. In a preferred embodiment, the viscosity-increasing agent is, or comprises, xanthan gum.
In other embodiments, the hydrocolloid is, or comprises a cross-linked hydrocolloid, for example a cross-linked polysaccharide, such as cross-linked alginate, pectin, carrageenan, gelatin, gellan, agar, agarose, modified starch, or a cellulose derivative, such as methyl cellulose or hydroxypropylmethyl cellulose.
The hydrocolloid may be cross-linked by any suitable method, for example including the methods for gelation of hydrocolloids described above: ionotropic gelation, cold-set gelation and heat-set gelation. In particular embodiments, molecules of the hydrocolloid are cross-linked by cations (for example calcium ions) as a result of ionotropic gelation of a hydrocolloid gelling agent. Examples of hydrocolloid cross-linked by cations that may be present in a composition of the invention include alginate, carrageenan or pectin.
In particular embodiments, a composition of the invention includes cross-linked alginate, for example alginate cross-linked by calcium ions. Alginate can form gels without prior heating because sodium alginate is soluble in cold water.
Cross-linked alginate may be formed from sodium alginate and calcium ions (for example, provided by calcium chloride). In some embodiments, water may be used as solvent to dissociate the calcium ions. However, since this could potentially activate production of hydrogen peroxide by the enzyme and the substance that includes a substrate for the enzyme, and limit the stability of the composition, it may be preferred to use a non-aqueous solvent to dissociate the calcium ions, such as ethanol or acetic acid.
We have appreciated that glycerol may be used to bind free water. This property allows water to be used to dissolve the alginate, provided sufficient glycerol is present to prevent premature release of hydrogen peroxide from the enzyme and the substance that includes a substrate for the enzyme.
In some embodiments, for example embodiments which include a viscosity-increasing agent such as xanthan gum, compositions of the invention may comprise a salt. The salt is preferably an inorganic or mineral salt. In a preferred embodiment, the salt is magnesium sulfate heptahydrate. Other suitable salts may include, but are not limited to, alkali metal salts, alkaline earth metal salts, transition metal salts, hydrates thereof, the like, and any combination thereof. Other specific examples of salts include magnesium chloride and its hydrated forms (e.g., MgCl2.6H2O), Magnesium acetate and its hydrated forms (e.g., Mg(OAc)2.4H2O), Zinc sulfate and its hydrated forms (e.g., ZnSO4.7H2O), sodium sulfate, sodium chloride and ammonium sulfate and any combination thereof. In certain embodiments, the salt is selected from the group consisting of magnesium sulfate, magnesium sulfate monohydrate, magnesium sulfate tetrahydrate, magnesium sulfate pentahydrate, magnesium sulfate hexahydrate, and magnesium sulfate heptahydrate.
Surprisingly, it has been found that salts such as magnesium sulfate heptahydrate can provide favourable rheological properties to compositions of the invention. For example, mixing a viscosity-increasing agent such as xanthan gum with a non-aqueous solvent, such as glycerol, may lead to a stringy solution. Adding a salt such as magnesium sulfate heptahydrate may improve the rheological properties of the solution such that it is less stringy and is more easily spread on a surface, such as skin. The inorganic salt may be a sulfate. The inorganic salt may be a magnesium salt.
According to the invention, there is provided a composition comprising a viscosity increasing agent (optionally xanthan gum), an oil (optionally paraffin oil), an emulsifier (optionally PGPR), a non-aqueous solvent (optionally glycerol), an enzyme that is able to convert a substrate to release hydrogen peroxide, a substance that includes a substrate for the enzyme (e.g. a sugar substance), and, optionally, an inorganic salt (e.g. magnesium sulfate heptahydrate).
The composition may comprise 0.1% to 1% (v/v) viscosity increasing agent (e.g. xanthan gum). The composition may comprise 48% (v/v) oil (e.g. v/v). The composition may comprise 0.5% to 5% (v/v) emulsifier (e.g. PGPR). The composition may comprise 0.05 to 0.5% (v/v) inorganic salt (e.g. magnesium sulfate heptahydrate).
According to the invention, there is provided a composition comprising an oil (optionally paraffin oil), an emulsifier (e.g. PGPR), an enzyme that is able to convert a substrate to release hydrogen peroxide and a substance that includes a substrate for the enzyme (e.g. a sugar substance). The composition may be formed by mixing the substance/enzyme (e.g. Surgihoney) with the oil in a ratio of 30:70 to 70:30 (by volume). Preferably, the ratio is at least 50:50 (by volume), for example 60:40 (by volume). A ratio in excess of at least 50:50 may afford higher stability of the emulsion. The composition may comprise 0.25-10% (v/v) emulsifier. The composition may comprise 0.25-5% (v/v) emulsifier. The composition may comprise 1-5% (v/v) emulsifier. The composition may comprise 1.5 to 3% (v/v) emulsifier. The composition may comprise 0.5-3% (v/v) emulsifier. The composition may comprise at least 1% (v/v) emulsifier.
There is also provided according to the invention a method of making a composition of the invention, which comprises mixing a lipophilic component, an aqueous component, an enzyme that is able to convert a substrate to release hydrogen peroxide, and a substance that includes a substrate for the enzyme to form the composition.
There is also provided, according to the invention, a method of making a composition of the invention, comprising mixing a first component (or liquid of a first phase), a second component (or liquid of a second phase), an enzyme that is able to convert a substrate to release hydrogen peroxide, and a substance that includes a substrate for the enzyme to form the composition, wherein the first component (or liquid of the first phase) and second component (or liquid of the second phase) are immiscible.
There is also provided according to the invention a method of making a composition of the invention, which comprises mixing an oil, an enzyme that is able to convert a substrate to release hydrogen peroxide, and a substance that includes a substrate for the enzyme to form the composition.
Methods of the invention may also comprise mixing a non-aqueous solvent, such as a polar, organic solvent.
A method of the invention may employ a rheometer to form compositions of the invention. A rheometer may allow for control of shear rate and temperature.
The enzyme, and the substance comprising a substrate for the enzyme may be dissolved in a non-aqueous solvent to form a first mixture. The emulsifier may be added to the first phase, lipophilic phase or oil to form a second mixture. The first mixture may then be added dropwise to the second mixture to form an emulsion, whilst being mixed using e.g. a rheometer or mixer.
To form an emulsion, mixing may occur at a shear rate of between 1500 1/s to 2500 1/s, such as 2000 1/s. Mixing may occur at 30 and 50° C., e.g. about 37° C.
There is further provided according to the invention a method of making a composition of the invention, which comprises mixing the enzyme, the substance that includes a substrate for the enzyme, liquid of the second phase, liquid of the first phase, and optionally an emulsifier, under a high rate of shear for sufficient time to form an emulsion.
More stable emulsions may be formed if the ingredients of the emulsion are pre-mixed before contact with the emulsifier. Thus, in some embodiments, the enzyme, the substance that includes a substrate for the enzyme, liquid of the second phase, and liquid of the first phase are pre-mixed under a high rate of shear before contacting the pre-mixed ingredients with the emulsifier and mixing of the mixture comprising the pre-mixed ingredients and the emulsifier under the high rate of shear.
In some embodiments, the enzyme and the substance that includes a substrate for the enzyme are dissolved in the liquid of the second phase to form a solution before contacting the solution with the liquid of the first phase.
The high rate of shear may be from 1000 1/s to 4000 1/s. We have found that emulsions made using methods of the invention are more stable when formed using a higher rate of shear, for example from >2000 1/s to 4000 1/s, >2000 1/s to 3500 1/s, >2500 1/s to 4000 1/s, or >2500 1/s to 3500 1/s.
Mixing of the enzyme, the substance that includes a substrate for the enzyme, liquid of the second phase, liquid of the first phase, and the emulsifier (if present) may be carried out at a temperature of 20° C. to 40° C., for example from 35° C. to 40° C. More stable emulsions may be formed when mixing of the enzyme, the substance that includes a substrate for the enzyme, liquid of the second phase, liquid of the first phase, and the emulsifier (if present) is carried out at higher temperatures, for example from >37.5° C. to 40° C., or 38° C. to 40° C.
In some embodiments of methods of the invention, the enzyme, the substance that includes a substrate for the enzyme, liquid of the second phase, liquid of the first phase, and the emulsifier (if present), are mixed under a high rate of shear for at least 5 minutes, for example for 5 to 30 minutes.
Methods of the invention may employ a high-speed homogeniser. For example, a homogeniser may be employed at a speed of at least 5,000 rpm, preferably at least 7,500 rpm, more preferably at around, or at least, 10,000 rpm. For instance, the speed may be about 7,500 rpm to 12,000 rpm. The use of a high-speed homogeniser may enable formation of smaller micelles, which in turn, may lead to formation of emulsions with improved stability.
For example, the diameter of the micelles may range from 5 to 100 μm, such as 10 to 50 μm. The average (mean) diameter of the micelles may be 5 to 100 μm, such as 10 to 50 μm.
Methods of the invention may comprise a pre-mixing step to disperse the emulsifier (e.g. a surfactant such as PGPR) in the first phase/first component (e.g. an oil such as paraffin). The emulsifier may be added to the first phase/first component. A homogeniser, preferably a high-speed homogeniser, may then be used to ensure adequate dispersion. The homogenisation may take place for at least 30 seconds, preferably at least one minute, more preferably at least 2 minutes.
Following the pre-mixing, a composition comprising the enzyme and the substrate, preferably pre-mixed with second phase/second component (e.g. a non-aqueous solvent such as glycerol), may be added slowly to the first phase/first component. For instance, the enzyme and substrate and second phase/second component may be added at a rate of 0.5 ml to 3 ml per minute, or at a rate of less than 5 ml, preferably less than 3 ml per minute.
Once the composition comprising the enzyme and substrate has been added, homogenisation (preferably high-speed homogenisation), may take place for at least 5 minutes, preferably at least 8 minutes, more preferably at least 10 minutes.
Methods of the invention may be used to form creams, for example by inclusion of a viscosity-increasing agent, such as a thickener or gelling agent, for example a hydrocolloid.
In some embodiments, a method of the invention further comprises mixing a viscosity-increasing agent with the enzyme, the substance that includes a substrate for the enzyme, liquid of the second phase, liquid of the first phase, and the emulsifier (if present), under the high shear rate to form a cream.
In some embodiments, the viscosity-increasing agent is, or comprises a hydrocolloid, for example a polysaccharide.
In some embodiments, the hydrocolloid is, or comprises a hydrocolloid thickener, such as starch, modified starch, xanthan, a galactomannan (such as guar gum, locust bean gum, and tara gum), gum Arabic or acacia gum, gum karaya, gum tragacanth, konjac maanan, or a cellulose derivative, such as carboxymethyl cellulose, methyl cellulose, or hydroxypropylmethyl cellulose.
In some embodiments, the hydrocolloid is, or comprises a hydrocolloid gelling agent, such as alginate, pectin, carrageenan, gelatin, gellan, agar, agarose, modified starch, or a cellulose derivative, such as methyl cellulose or hydroxypropylmethyl cellulose.
The hydrocolloid gelling agent may capable of forming a gel by ionotropic gelation in the presence of cations. In such embodiments, a method of the invention further comprises mixing the cations with the hydrocolloid gelling agent, the enzyme, the substance that includes a substrate for the enzyme, liquid of the second phase, liquid of the first phase, and the emulsifier (if present), under the high shear rate to form the cream.
In some embodiments, the hydrocolloid gelling agent capable of forming a gel by ionotropic gelation, the enzyme, the substance that includes a substrate for the enzyme, liquid of the second phase, liquid of the first phase, and the emulsifier (if present), are mixed to form a mixture prior to contacting the cations with the mixture.
In some embodiments the hydrocolloid gelling agent capable of forming a gel by ionotropic gelation is contacted with the liquid of the second phase, the enzyme, and the substance that includes a substrate for the enzyme, prior to contact with the liquid of the first phase.
In some embodiments the cations are, or comprise calcium ions.
In particular embodiments the hydrocolloid gelling agent capable of forming a gel by ionotropic gelation in the presence of cations is, or comprises alginate, carrageenan or pectin, for example alginate.
In a particular embodiment, the hydrocolloid gelling agent is provided in aqueous solution, and the second phase is glycerol, wherein the glycerol is present in sufficient amount to bind free water in the composition and thereby prevent the enzyme catalysing release of hydrogen peroxide from the substance that includes a substrate for the enzyme.
In some embodiments the hydrocolloid gelling agent that is able to form a gel by ionotropic gelation (for example, alginate) is pre-mixed with the substance that includes a substrate for the enzyme, liquid of the second phase, and liquid of the first phase under a high rate of shear before the pre-mixed ingredients are contacted with the emulsifier (if present) and the cations (for example, calcium ions), and the mixture comprising the pre-mixed ingredients, the emulsifier (if present), and the cations is mixed under the high rate of shear.
The emulsifier (if present) may be contacted with the pre-mixed ingredients before the cations (for example, calcium ions). The cations (for example, calcium ions) may be added dropwise.
The cations (for example, calcium ions) may be provided in aqueous solution. Alternatively, the cations may be provided in non-aqueous solution, using a non-aqueous solvent, such as ethanol or acetic acid.
In particular embodiments, calcium chloride is provided in ethanol, and sodium alginate is provided in aqueous solution, and the second phase is glycerol, and the glycerol is present in sufficient amount to bind the free water in the alginate solution and thereby prevent the enzyme catalysing release of hydrogen peroxide from the substance that includes a substrate for the enzyme. This prevents premature release of hydrogen peroxide until the composition is contacted with water, thereby providing a stable composition.
As above, a method of the invention may employ a rheometer to form a composition of the invention. A rheometer may allow for control of shear rate and temperature. Alternatively, a high rate of shear may be provided by use of an ultrasonic probe, or a homogeniser.
There is also provided according to the invention, a pharmaceutical composition comprising a composition of the invention and a pharmaceutically acceptable carrier, excipient or diluent.
There is also provided according to the invention a composition of the invention for use as a medicament.
There is further provided according to the invention a composition of the invention for use in the prevention or treatment of a microbial infection.
The prevention or treatment is preferably by topical administration of the composition. The prevention or treatment may be by administration to a subject's respiratory tract. The prevention or treatment may be by administration to the body cavity. The prevention or treatment may be by internal administration to a subject.
There is also provided according to the invention a method of prevention or treatment of a microbial infection, which comprises administering an effective amount of a composition of the invention to a subject in need of such treatment.
The invention also provides use of a composition of the invention in the manufacture of a medicament for the prevention or treatment of a microbial infection.
The microbial infection may be a viral infection, for example, a herpes simplex virus (HSV) infection. In other embodiments, the microbial infection may be a fungal infection, or a bacterial infection.
The microbial infection may be: a nasal infection, such as sinusitis or rhinosinusitis; a respiratory tract infection, such as an upper respiratory tract infection (e.g. tonsillitis, laryngitis or sinusitis) or a lower respiratory tract infection (e.g. bronchitis, pneumonia, bronchiolitis or tuberculosis); an infection associated with chronic obstructive pulmonary disease (COPD), cystic fibrosis, bronchiectasis, asthma, or an HIV/AIDS-associated respiratory infection, or a respiratory infection associated with terminal disease.
A composition of the invention may be used to prevent or treat a microbial infection that comprises a biofilm, or a microbe that is capable of forming a biofilm. The biofilm may comprise a biofilm-forming bacterium, fungus, or virus. The microbe that is capable of forming a biofilm may be a bacterium, fungus, or virus.
A composition of the invention may be used in an antimicrobial wipe, in disinfection, for example in hospital disinfection, or as an antimicrobial spray, for example as a topical prophylactic antimicrobial spray to disinfect part of the body of a patient prior to surgery.
A composition of the invention may include an antimicrobial agent. For example, hydrogen peroxide may be present if the composition is formed by contacting the enzyme with the substance in aqueous solution under conditions for conversion of the substrate by the enzyme, and then drying the composition to reduce its water content to a level where there is insufficient free water to allow the enzyme to convert the substrate. Preferably, however, the composition does not include any detectable hydrogen peroxide. Such composition may be formed, for example, by contacting the enzyme with the substrate in the absence of sufficient free water to allow the enzyme to convert the substrate. Examples of other antimicrobial agents that may be present in a composition (e.g. a storage-stable composition) of the invention include: an antibiotic, an antiviral agent, or an anti-fungal agent.
Preferably, compositions of the invention comprise substantially no hydrogen peroxide, or no detectable hydrogen peroxide. For example, hydrogen peroxide is preferably not detectable using a hydrogen peroxide test strip, such as a Quantofix® peroxide test stick (Sigma Aldrich, UK). For example, hydrogen peroxide may present at a level less than 1 ppm, or at a level less than 0.5 ppm. Hydrogen peroxide may be at a level less than 0.1 ppm.
The composition may be a medical grade or medical device grade composition, or a pharmaceutical grade composition.
Each component of the composition may be a natural substance (i.e. each component is derived or purified from a natural source). Compositions for use according to the invention which contain only natural ingredients provide an attractive alternative to drug-based antimicrobial formulations.
Advantageously the substance is a honey. The honey may be a medical grade or medical device grade honey. In some embodiments, the honey is a honey that has been treated to remove or inactivate catalase activity originally present in the honey. According to an embodiment of the invention, the substance is a pasteurised honey, and the enzyme is a glucose oxidase. According to some embodiments, the substance is a medical grade or medical device grade honey, and the enzyme is a medical grade or medical device grade enzyme, suitably glucose oxidase.
Honey is a natural product made by honey bees using nectar from flowers. It is a saturated or super-saturated solution of sugars. Honey is defined in the Codex Alimentarius international food standard as “the natural sweet substance produced by honey bees from the nectar of plants or from secretions of living parts of plants or excretions of plant sucking insects on the living parts of plants, which the bees collect, transform by combining with specific substances of their own, deposit, dehydrate, store and leave in the honey comb to ripen and mature” (Revised Codex Standard for Honey, 2001).
Nectar typically includes approximately 14% simple sugars (w/w), 1% phenol compounds, and 85% water. The phenol compounds give the honey its taste, aroma and colour. In the warm conditions of the hive, typically 36° C., the nectar would very quickly ferment. To prevent this, the nectar is mixed with secretions, containing enzymes, from the salivary and hypopharyngeal glands of foraging bees. In the hive the nectar is passed from bee to bee and more secretions are added before it is stored in the cells of the hive. The amount of enzymes present varies with the age, diet and physiological stage of the bees (when a bee is a forager its glands produce more digestive enzymes), strength of the colony, temperature of the hive, and the nectar flow and its sugar content.
The enzymes added to nectar by bees include diastase, which catalyses the conversion of starch to dextrin and sugar, Invertase, which catalyses the conversion of sucrose to fructose and glucose, and glucose oxidase, which catalyses the conversion of glucose to hydrogen peroxide and gluconic acid. Low doses of hydrogen peroxide prevent the growth of yeasts that would quickly ferment the nectar. As the bees progressively dry the nectar to form honey, the gluconic acid makes the honey acidic (between pH 3.5 and 4.5). Water is effectively trapped to the sugar molecules in the honey and is not available for further chemical reactions. The amount of ‘free’ water in honey is measured as the water activity (aw). The range of aw found in honey has been reported to be 0.47-0.70, with mean values of 0.562 and 0.589 (RCIEGG, M; BLANC, B, 1981, The water activity of honey and related sugar solutions. Lebensmittel-Wissenschaft and Technologie 14: 1-6). The aw of ripened honey is too low to support the growth of any species, with no fermentation occurring if the water content is below 17.1% (Molan, P. C. (1992). The antibacterial activity of honey: 1. The nature of the antibacterial activity. Bee World, 73(1), 5-28). The acidity of the honey and the lack of free water prevent the further risk of fermentation, and stop the glucose oxidase working. Honey also contains variable amounts of catalase originating from the nectar.
A typical chemical composition of blossom honey is:
In addition, trace amounts of pollen are present, which can be used to identify the botanical origin of the honey, as well as the enzymes invertase, diastase, catalase, and glucose oxidase. There is also phytochemical component. This varies but is typically up to ˜1%, depending on the source of the honey.
Once diluted, the glucose oxidase present in natural honey is able to convert glucose substrate in the diluted honey to release hydrogen peroxide. However, the variability in the content of honey (particularly in the content of glucose oxidase activity, glucose, and catalase activity) means that honeys from different sources, or different harvests of honey from the same source, can be very variable in their antimicrobial effectiveness.
According to an embodiment of the invention, the honey may be pasteurised. Pasteurisation of honey inactivates the catalase and glucose oxidase activity present in the honey. Optionally, the pasteurised honey may be filtered to remove any particles (such as wax particles and bee wings) that may be in the honey post-harvest. To form a storage-stable composition of the invention, a glucose oxidase is contacted with the pasteurised honey once it has cooled to a temperature (suitably 35-40° C.) that will not inactivate the added glucose oxidase and at which the honey remains sufficiently liquid to facilitate mixing with glucose oxidase.
Honey can be pasteurised at a temperature that is sufficient for the heat inactivation of catalase activity. A suitable minimum temperature is from 60° C. to 80° C. This temperature should be maintained preferably for at least two minutes.
The control of the heat process may be important, since a bi-product of heating honey is the formation of HMF (HydroxyMethylFurfuraldehyde) which is used as an indicator of heat and storage changes in honey. HMF is formed by the breakdown of fructose in the presence of acid. Heat increases the speed of this reaction. The increase in speed is exponential with increasing heat. For every degree that the honey is raised above 40° C., close to the normal hive ambient temperature, HMF increases rapidly. HMF is not a harmful product. Jams, Molasses, Golden Syrup etc. can have levels of HMF 10 to 100 times that of honey. However HMF levels are used as an indication of degradation of honey and under the Codex Alimentarius Standard 40 mg/I is the maximum permissible level in the EU for table honey.
To prevent the build up of HMF it is preferred that the honey is raised rapidly to temperature levels to inactivate the catalase and then the honey is brought quickly down in temperature to a maximum of between 40 and 45° C. using a heat exchange mechanism.
No water is added during the process of this preferred embodiment, and so the resulting composition does not include sufficient free water to allow the glucose oxidase to convert the glucose present to release hydrogen peroxide. The storage-stable composition comprises:
pasteurised honey, and added glucose oxidase. There is no detectable hydrogen peroxide present. The composition can be stored at ambient temperature for at least several days.
In other embodiments of the invention, the honey may be unpasteurised.
According to some preferred embodiments, the honey (pasteurised or unpasteurised) is a creamed honey. Creamed honey is a honey that has been processed to control crystallization.
Creamed honey contains a large number of small crystals, which prevent the formation of larger crystals that can occur in unprocessed honey. A method for producing creamed honey was described in U.S. Pat. No. 1,987,893. In this process, raw honey is first pasteurised, then previously processed creamed honey is added to the pasteurized honey to produce a mixture of 10% creamed honey and 90% pasteurised honey. The mixture is then allowed to rest at a controlled temperature of 14° C. This method produces a batch of creamed honey in about one week. A seed batch can be made by allowing normal honey to crystallize and crushing the crystals to the desired size. Large scale producers have modified this process by using paddles to stir the honey mixture while holding the mixture at 14° C. In alternative creaming methods, the pasteurisation step may be omitted, with the honey instead being slowly warmed to 37° C.
In other embodiments of the invention, the honey (pasteurised or unpasteurised) is an uncreamed honey. For example, the honey may be a pasteurised, uncreamed honey.
The glucose oxidase may be a purified natural glucose oxidase preparation which is of medical grade or medical device grade for medical applications. The activity of the glucose oxidase may be selected depending on the desired rate of production of hydrogen peroxide following dilution of the composition. Several glucose oxidase preparations are commercially available (glucose oxidase is identified by the reference CAS:9001-37-0). Common microbial sources for glucose oxidase from non genetically modified organisms include selected strains of Aspergillus niger, Penicillium amagasakiense, Penicillium variabile, Penicillium notatum. Medical device grade glucose oxidase, from GMO Aspergillus niger, is available from Biozyme UK, activity 240 iu/mg. Food standard glucose oxidase, from Aspergillus niger, is available from BIO-CAT INC, activity 15,000 Units/g. Non-Genetically Modified glucose oxidase is available from BIO-CAT INC, activity 12,000/g. Glucose oxidase (GO3B2), from Apsergillus niger, is available from BBI Enzymes Limited, activity 360 Units/mg. Contaminants: alpha amylase no greater than 0.05%, Saccharase no greater than 0.05%, maltase no greater than 0.05% and GO/Cat no less than 2000.
Compositions of the invention may comprise 25 to 2000 ppm of the enzyme, for example 50 to 1000 ppm of the enzyme. Compositions of the invention may comprise 750 to 2000 ppm of the enzyme. Compositions of the invention may comprise at least 500 ppm of the enzyme. Compositions of the invention may comprise 250 to 1500 of the enzyme.
The enzyme activity (for example, the glucose oxidase activity) may range, for example, from 1-400 IU/mg, or 1-300 IU/mg, for example 250-280 IU/mg. The amount of enzyme used is likely to depend on several factors, including the desired use of the composition, the amount of any catalase activity present in the substance, the amount of substrate present in the substance, the desired level of hydrogen peroxide release, and the desired length of time for hydrogen peroxide release. A suitable amount of enzyme can readily be determined by a person of ordinary skill in the art, if necessary using a well diffusion assay, to determine the extent of hydrogen peroxide release for different amounts of enzyme. Suitable amounts of enzyme (such as glucose oxidase) may be from 0.0001% to 0.5% w/w of the composition. The amount of enzyme used may be selected so as to produce a composition for generating antimicrobial activity that is equivalent to a selected phenol standard (for example a 10%, 20%, or 30% phenol standard).
Compositions of the invention, particularly compositions in which the substance is honey (for example, unpasteurised honey), and the enzyme is glucose oxidase that is able to convert D-glucose in the honey to release hydrogen peroxide, may comprise at least 1 unit, and preferably up to 1500 units, of glucose oxidase per gram of the composition. The glucose oxidase is additional (i.e. added as a result of human intervention) to any glucose oxidase activity that may naturally be present in the substance.
A “unit” is defined herein as the amount of enzyme causing the oxidation of 1 micromole of glucose (or other enzyme substrate) per minute at 25 degrees centigrade at pH 7.0.
The Applicant has found that the antimicrobial potency of compositions of the invention may be increased simply by increasing the amount of glucose oxidase activity present in the composition.
In some embodiments of the invention, a composition of the invention comprises more than 15 units, for example at least 30 units, at least 50 units, or at least 100 units, and suitably less than 685 units, for example 100-500 units, of glucose oxidase per gram of the composition. Such compositions have been found to have superior antimicrobial properties than compositions with up to 15 units of glucose oxidase per gram of the composition. In particular, such compositions have increased potency against a wide range of microorganisms, including MSSA, MRSA, Group A and B Streptococci, Enterococcus, E. coli, E. coli ESBL, Serr.liquefaciens Amp C, Kleb.pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, and Candida albicans.
In other embodiments of the invention, a composition of the invention comprises at least 500 units, for example 500-1000 units, or 685-1000 units, of glucose oxidase per gram of the composition. Such compositions have been found to have even more superior antimicrobial properties. In particular such compositions have further increased potency against a wide range of microorganisms, including Staphylococcus aureus, MSSA, MRSA, Group A and B Streptococci, Enterococcus, E. coli, E. coli ESBL, Serr.liquefaciens Amp C, Kleb.pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, and Candida albicans.
Compositions of the invention can be used to treat any microbial infection that can be treated by hydrogen peroxide. Examples include infection caused by gram positive bacteria, gram negative bacteria, acid-fast bacteria, viruses, yeasts, parasitic or pathogenic micro-organisms or fungi. In particular, infections caused by the following micro-organisms may be treated: Escherichia co/i, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Propionibacterium acnes, Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus saprophytics, Beta haemolytic Streptococci Group A or B, Campylobacter coli, Campylobacter jejuni, Methicillin Resistant Staphylococcus Aureus (MRSA), Methicillin Sensitive Staphylococcus Aureus (MSSA), Botrytis cinerea, Mycobacterium tuberculosis, Cryptosporidium, Plasmodium, and Toxoplasma.
The pasteurisation process inactivates any enzyme activity present in the honey, and so there is no variability in catalase and substrate conversion activity between pasteurised honeys from different sources, or between different harvests of honey from the same source. The amount of substrate conversion activity can be controlled by addition of a purified glucose oxidase preparation with a defined amount and activity of the enzyme. Thus, the inherent variability in antimicrobial properties between different types and harvests of honey is considerably reduced, and the antimicrobial properties of honeys with low antimicrobial potency are improved.
Compositions of the invention may be administered at an appropriate frequency determined by the subject or a healthcare provider. Suitably compositions of the invention may be administered at least every several days, for example every week, but preferably several times a day, every day, or every other day.
The amount of a composition of the invention administered will depend on many factors, such as the strength of the antimicrobial properties of the composition, and on the age and condition of the subject to be treated. However, for many applications it is expected that each administration comprises 0.1-100 g, 0.5-100 g, 1-100 g, 2-100 g, 5-100 g, 0.1-10 g, 0.5-10, or 1-10 g of a composition of the invention.
According to preferred embodiments of the invention, a composition of the invention is sterile.
Compositions of the invention may be sterilised by any suitable means. The Applicant has found that compositions comprising glucose oxidase retain glucose oxidase activity (and, therefore, the ability to release hydrogen peroxide on dilution) following sterilisation by exposure to gamma irradiation or electron beam irradiation. A suitable level of gamma irradiation is 10-70 kGy, preferably 25-70 kGy, more preferably 35-70 kGy. A suitable level or dose of irradiation (e.g. electron beam irradiation) may be 10-100 kGy, preferably 30-80 kGy, more preferably 50-80 kGy. The dose may be greater than 35 kGy. The dose may be less than 80 kGy, for example 75 kGy or less. In one embodiment, compositions of the invention may be sterilised by irradiation that is not gamma irradiation.
There is also provided according to the invention a method of sterilising a composition of the invention, which comprises exposing the composition to radiation, preferably gamma radiation or electron beam radiation.
Compositions of the invention preferably have not been sterilized by ozonation, and do not include ozone, or any components that have been subjected to sterilisation by ozonation. In particular, compositions of the invention should not comprise ozonized honey or ozonated oil.
Sterilised compositions of the invention that are stored away from exposure to light are expected to retain stability for at least six months. For example, such compositions may be packaged in high-density polyethylene/low-density polyethylene (HDPE/LDPE) tubes or in polyester-aluminium-polyethylene (PET/Al/PE) sachets.
A composition of the invention is preferably a medical grade or medical device grade composition. Preferably the unrefined natural substance is a honey, suitably a medical grade or medical device grade honey.
Preferably a composition of the invention comprises a creamed honey, more preferably a creamed unpasteurised honey. Such compositions can readily be administered topically because the presence or number of large crystals has been minimised by the creaming process.
For compositions of the invention that comprise honey, it will be appreciated that there may be no need to use pasteurised honey in the composition if the composition is sterilised. It may instead be preferable to use unpasteurised honey (preferably creamed honey) or other unrefined natural substance. In some embodiments, compositions of the invention comprise unpasteurised honey, and added purified glucose oxidase.
Thus, a storage-stable composition of the invention may comprise unpasteurized honey, and added purified glucose oxidase that, in the presence of sufficient free water, is able to convert D-glucose in the honey to release hydrogen peroxide, wherein the composition does not include sufficient free water to allow the glucose oxidase to convert the D-glucose.
Such compositions may comprise at least 1 unit, and for example up to 1500 units, of glucose oxidase per gram of the composition. Suitably such compositions comprise more than 15 units of glucose oxidase per gram of the composition, for example at least 100 units, or 100-500 units, of glucose oxidase per gram of the composition, or at least 500 units, or 500-1000 units, of glucose oxidase per gram of the composition.
The honey of such compositions may comprise a creamed unpasteurized honey.
A composition of the invention may be a pharmaceutical composition comprising a pharmaceutically acceptable carrier, excipient, or diluent.
A composition of the invention may be in a form suitable for administration to a human or animal subject. Suitable forms include forms adapted for topical administration. Forms suitable for topical administration include a topical ointment, cream, lotion, oil, liniment, liquid, gel, or a dissolvable strip. If a storage-stable composition is used, this may be diluted by liquid present at the site of administration (for example, by saliva), leading to release of hydrogen peroxide at the administration site.
A composition of the invention may be present with at least one suitable antimicrobial or immunostimulatory component, excipient or adjuvant, or any other suitable component where it is desired to provide ability to generate antimicrobial activity. Preferably, however, the compositions do not include any antibiotic.
A composition of the invention may comprise “Surgihoney”. Surgihoney is unpasteurised honey with added purified glucose oxidase. Three different preparations of Surgihoney have been made with different antimicrobial potencies:
SH1 Surgihoney: unpasteurised honey with 0.1% (w/w) added glucose oxidase. The enzyme used was food grade glucose oxidase, from Aspergillus niger, from BIO-CAT, INC, activity 15,000 Units/g. Sealed sachets of the SH1 Surgihoney were gamma irradiated at a target dose of 11/6-14.2 kGy.
SH2 Surgihoney: unpasteurised honey with 0.1% (w/w) added glucose oxidase. The enzyme used was glucose oxidase (GO3B2), from Aspergillus niger, from BBI Enzymes Limited, activity 274 Units/mg. Unit Definition: the amount of enzyme causing the oxidation of 1 micromole of glucose per minute at 25 degrees centigrade at pH 7.0. Contaminants: alpha amylase no greater than 0.05%, Saccharase no greater than 0.05%, maltase no greater than 0.05% and GO/Cat no less than 2000.
SH3 Surgihoney: unpasteurised honey with 0.25% (w/w) added glucose oxidase. The enzyme used was glucose oxidase (GO3B2) from BBI Enzymes Limited, activity 274 Units/mg.
Thus, SH1 Surgihoney contains 15 units of glucose oxidase per gram of the composition, SH2 Surgihoney contains 274 units of glucose oxidase per gram of the composition, and SH3 Surgihoney contains 685 units of glucose oxidase per gram of the composition.
In some embodiments, a composition of the invention (in particular, a composition of the invention that comprises honey and added glucose oxidase—referred to below as “Active honey”) is not, or does not comprise the following:
Active honey 25%
White petrolatum
Light liquid paraffin
Zinc oxide
In some embodiments, a composition of the invention (in particular, a composition of the invention that comprises honey and added glucose oxidase—referred to below as “Active honey”) is not, or does not comprise the following:
In some embodiments, a composition of the invention (in particular, a composition of the invention that comprises honey and added glucose oxidase—referred to below as “Active honey”) is not, or does not comprise the following:
15%
In some embodiments, a composition of the invention does not comprise:
A cream formulation comprising Surgihoney SH1 was made with the following ingredients:
In some embodiments, a composition of the invention does not comprise an emulsion comprising the following ingredients:
In some embodiments, a method of the invention does not comprise the following method for preparation of a Surgihoney emulsion, as recited in Example 7:
10 g Surgihoney was dissolved in 10 ml of glycerol. 10 ml of paraffin oil was then added to a Rheometer (TA Instruments AR-G2) which had a Jacket Peltier and vane geometry attached. 1 ml of PGPR (Polyglycerol polyricinoleate) was then added. The rheometer was then started under the following conditions; Shear rate 2000 1/s, Temperature set at 37.5° C. After 2 minutes, 10 ml of Surgihoney-glycerol solution was added dropwise. Once a total of 10 minutes had elapsed the emulsion was transferred from the Jacket Peltier to a container.
Embodiments of the invention are now described, by way of example only, with reference to the accompanying drawings in which:
Surgihoney may also be referred to as Surgihoney™, SurgihoneyRO, SurgihoneyRO™ or SHRO. Compositions of the invention (or for use in the invention), such as compositions which comprise purified glucose, purified fructose and glucose oxidase may be referred to as SyntheticRO, synthetic honey compositions or synthetic compositions.
A cream formulation comprising Surgihoney SH1 was made with the following ingredients:
The cream remains stable for many years, as judged by its ability to produce hydrogen peroxide when contacted with water.
SH1 or SH2 Surgihoney was mixed with Herpes Simplex Virus Type 1 or 2 (HSV 1 or HSV 2) in cell culture medium (a 50% mixture of honey and virus in cell culture medium) and then incubated for 1 hour at 37° C. A dilution series was then made from the mixture, and the dilutions were plated onto Vero cells. SH1 Surgihoney reduced the titre of virus by 1 log. SH2 Surgihoney was virucidal for both HSV 1 and HSV 2 (>6 log drop in titre). The experiment was repeatable.
SH1 or SH2 Surgihoney was mixed with Herpes Simplex Virus (HSV) (50 μg honey and 50 μl virus) and incubated for 1 hour at 37° C. A dilution series (10−2, 10−3, 10−4, 10−5) was then made from the mixture, and the dilutions were used in a plaque reduction assay. Controls with no honey, or with control honey were also performed. The number of viral plaques formed for each dilution was recorded. The results are shown in the Table below.
The results show that SH1 and SH2 Surgihoney was strongly virucidal against HSV in both experiments.
SH1 or SH2 Surgihoney (50 μg honey diluted 10−2, 10−3, 10−4, 10−5) was incubated on cells for 2 days. The number of live cells, and the total number of cells was counted (percentage viability=live/total×100). The results are shown in the table below, and in
The results show that SH1 Surgihoney was cytotoxic at the 10−2 dilution, and cytostatic at the 10−3 and 10−4 dilutions, and that SH2 Surgihoney was cytostatic at the 10−2, 10−3 and 10−4 dilutions. SH1 and SH2 Surgihoney were not cytotoxic or cytostatic at the 10−5 dilution.
It is concluded from the results in Examples 3 and 4 that Surgihoney can be administered at doses which are virucidal but not cytotoxic or cytostatic.
The antimicrobial activity of Surgihoney (SH) and two prototype modified honeys made by Apis mellifera (honeybee) against Staphylococcus aureus (NCIMB 9518) was tested. We also examined a number of modified types of Surgihoney for the ability to change the level of production of hydrogen peroxide from the samples.
Methods: Surgihoney (SH) was compared with two modified honeys, Prototype 1 (PT1) and Prototype 2 (PT2) using a bioassay method against a standard strain of Staphylococcus aureus. Further work studied the rate of generation of hydrogen peroxide from these preparations.
Results: Surgihoney antimicrobial activity was shown to be largely due to hydrogen peroxide production. By modification of Surgihoney, two more potent honey prototypes were shown to generate between a two- and three-fold greater antibacterial activity and up to ten times greater peroxide activity.
Conclusions: Surgihoney shows good antimicrobial activity. Two further honey prototypes have been shown to have antimicrobial activity that is possible to be enhanced due to demonstrated increases in peroxide activity.
The antibacterial activity of Surgihoney (S) and two modified honeys, Prototype 1 (PT1) and Prototype 2 (PT2) was measured using Staphylococcus aureus (NCIMB 9518) and expressed as the equivalent percentage phenol. Values were calculated of the mean from three sample replicates tested, repeated on three days.
Assay Method. The agar well diffusion method used was adapted from the punch plate assay for inhibitory substances described in the Microbiology Standard Methods Manual for the New Zealand Dairy Industry (1982) [Bee Products Standards Council: Proposed standard for measuring the non-peroxide activity of honey. In. New Zealand: Bee Products Standards Council; 1982.].
Inoculum Preparation. Overnight culture was adjusted to an absorbance of 0.5 measured at 540 nm using sterile nutrient broth as a blank and a diluents and a cuvette with a 1 cm pathway.
Assay Plate preparation. A volume of 100 μl of the culture adjusted to 0.5 absorbance was used to seed 150 ml nutrient agar to make the assay plates. The agar was swirled to mix thoroughly and poured into large petri dishes which had been placed on a level surface. As soon as the agar was set the plates were placed upside down overnight before using the next day. For assay these seeded plates were removed from 4° C. and allowed to stand at room temperature for 15 min before cutting 7.0 mm diameter wells into the surface of the agar. 250 μl of test material (sample or standard) was placed into each well.
Catalase solution. A 200 mg/ml solution of catalase from bovine liver (Sigma C9322, 2900 units/mg) in distilled water was prepared fresh each day.
Sample preparation. Primary sample solutions were prepared by adding 4 g of sample to 4 ml of distilled water in universals and placed at 37° C. for 30 minutes to aid mixing. To prepare secondary solutions, 2 ml of the primary sample solution was added to 2 ml of distilled water in universals and mixed for total activity testing and 2 ml of the primary sample solution was added to 2 ml of catalase solution and mixed for non-peroxide activity.
Preparation of phenol standards. Standards (w/v) 10%, 30%, 50% phenol were prepared by dissolving phenol in water. Phenol standards were brought to room temperature in the dark before use and were mixed thoroughly before addition to test wells. Each standard was placed in three wells to test in triplicate. Standards were kept at 4° C. with an expiry date of one month.
Sample and standard application. All samples and standards were tested in triplicate by adding 250 μl to each of 3 wells.
Plate incubation. After application of samples the plates were incubated for approximately 18 hours at 37° C. The diameter of inhibition zones, including the diameter of the well (7.0 mm), was recorded.
Calculation of antibacterial activity of samples. The mean diameter of the clear zone around each phenol standard was calculated and squared. A standard graph was plotted of % phenol against the square of the mean diameter of the clear zone. A best-fit straight line was obtained using linear regression and the equation of this line was used to calculate the activity of each diluted honey sample from the square of the mean measurement of the diameter of the clear zone. To allow for the dilution (assuming the density of the Surgihoney to be 1.35 g/ml) this figure was multiplied by a factor of 4.69 and the activity of the samples was then expressed as the equivalent phenol concentration (% w/v).
Total Activity: all the activity, including activity due to hydrogen peroxide (H2O2).
Non-Peroxide Activity: H2O2 is removed by treating samples with catalase enzyme.
2. Determination of Honey Activity by H2O2 Method
The activity was measured using the Merckoquant® 1.10011. & 1.10081.
Peroxide Test Kits. Concentrations expressed as the equivalent mg/L H2O2.
Samples were diluted 1:10 with purified water. Following 5 min incubation, all samples were measured for H2O2 production each hour over a 12 hour period followed by 24 and 48 hour time points.
Method of Determination. Peroxidase transfers oxygen from the peroxide to an organic redox indicator, which is then converted to a blue coloured oxidation product. The peroxide concentration is measured semi-quantitatively by visual comparison of the reaction zone of the test strip with the fields of a colour scale. The reaction zone of the test strip is immersed into the Surgihoney sample for 1 sec, allowing excess liquid to run off the strip onto an absorbent paper towel and after 15 seconds (Cat. No. 110011), 5 seconds (Cat. No. 110081), after which a determination of the colour formed in the reaction zone more precisely coincided with the colour fields scale.
The antimicrobial activity produced by the modification of the honey samples resulted in a two-fold and almost three-fold respectively increase in phenol activity with PT1 and PT2 compared with Surgihoney alone. The results for the three samples of Surgihoney (SH) and two modified prototypes, PT1 and PT2 are shown in the Table below.
2. Determination of Honey Activity by H2O2 Method
The prototype modifications are observed to generate up to seven and ten times the hydrogen peroxide activity of Surgihoney. The results for the three samples are shown in
The results from this work show that the main antimicrobial activity of Surgihoney and two modified prototypes, PT1 and PT2 are due to hydrogen peroxide. This is a similar finding to certain other honeys from a variety of floral sources. However, unlike previous work the availability of hydrogen peroxide from the samples is able to be enhanced and at 12 hours is seven and ten times respectively the value for Surgihoney alone. There is a striking linear relationship between the antimicrobial activity and the maximum output of hydrogen peroxide from the three honey prototypes.
This peroxide activity offers potent antimicrobial activity that is ideally suited to treat or prevent microbial infections. Hydrogen peroxide is an effective antimicrobial and is already used as a biocide for its potent activity against vegetative bacteria, yeasts and spores. It produces its antimicrobial effect through chemical oxidation of cellular components.
The human toxicity of hydrogen peroxide is concentration dependent and one study has claimed that the differential concentrations for antimicrobial and human toxicity might overlap. By contrast, certain preparations of honey have been shown to be an effective antimicrobial agent by supplying low concentrations of hydrogen peroxide continuously over time rather than as a large amount and without such toxicity. Indeed there is compelling evidence that where physiological levels of hydrogen peroxide are applied to mammalian cells there is a stimulation of biological responses and activation of specific biochemical pathways in these cells.
Clearly Surgihoney and the two modified prototypes, PT1 and PT2 offer effective hydrogen peroxide release over at least 24 hours.
Surgihoney and the two modified prototypes, PT1 and PT2 have been shown to have potent antimicrobial activity against a standard strain of Staphylococcus aureus. These antimicrobial activities have been shown to be due to hydrogen peroxide. The activity is scalable and can be described in terms of hydrogen peroxide activity. These modified honeys are effective, non-toxic and easy to administer.
This example describes susceptibility testing of a range of bacterial isolates to Surgihoney by disc diffusion method, minimum inhibitory concentration (MIC) and minimum cidal concentration (MBC) determination, and time bactericidal measurements.
Results: Surgihoney demonstrates highly potent inhibitory and cidal activity against a wide range of Gram positive and Gram negative bacteria and fungi. MIC/MBC's are significantly lower than concentrations likely to be achieved in topical clinical use. Surgihoney 1 MIC/MBC's for Staph. Aureus are 31 and 125 gms/L and Surgihoney 3 MIC/MBC's 0.12 and 0.24 gms/L. Cidal speed depends on the potency. In Surgihoney 1, the least potent, complete cidal activity occurs for all organisms tested within 48 hours. For Surgihoney 3, the most potent, cidal activity occurs within 30 minutes. Maintenance of the Surgihoney inoculums preparation for up to a week demonstrated complete cidal activity and no bacterial persistence.
Conclusions: Surgihoney has wide potential as a highly active topical treatment combining the effects of the healing properties of honey with the potent antimicrobial activity of the bioengineered product. It is highly active against multidrug resistant bacteria. It is more active than other honeys tested and comparable to chemical antiseptics in antimicrobial activity.
This study examines the in-vitro properties of Surgihoney. Surgihoney retains all the established healing properties of natural honey but its antimicrobial activity can be set at whichever potency is required. This study determined minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of Surgihoney 1, 2 and 3 and time kill curves.
Surgihoney was provided as potency grades 1, 2 and 3. It was presented as a sterile pharmaceutical grade product in a sachet in semisolid form.
Clinical isolates were collected from soft tissue microbiology samples. Eighteen isolates of Staphylococcus aureus, 12 methicillin-sensitive (MSSA) and 6 methicillin-resistant (MRSA), 6 isolates of β haemolytic streptococci, Lancefield groups A (2), B (2), C (1), G (1), 5 isolates of Enterococcus spp. Including vancomycin-resistant E. faecium, 6 of Esch. coli, including extended spectrum β lactamase producers, 2 of Klebsiella spp., 1 Serratia Marcescens Amp C producer, 4 of Pseudomonas aeruginosa, 1 of Acinetobacter lwoffii, 1 of Propionibacterium acnes, 1 Bacteroides fragilis, and 2 of Candida albicans, 1 of Candida glabrata, 1 of Aspergillus fumigates were tested against Surgihoney.
Six mm wells were cut in isosenitest agar which had already been inoculated with the test organism at a concentration to give a semiconfluent growth. Test Surgihoney and other honeys in the pilot study were added to the wells.
A pilot study was carried out initially to compare Surgihoney potencies 51, S2, S3 with a variety of honeys from around the world, European, South American, New Zealand, Yemani, Sudanese and with medical honey, Medihoney and with antimicrobial dressings containing silver (Silver Aquacell) and iodine (Iodoflex). Wells were cut in the plates inoculated with Staphylococcus aureus and filled with test honey or in the case of the dressings, these were cut to 2×2 cm and placed on the surface of the inoculated plates.
Following the pilot studies the Surgihoney potencies 51, S2, S3 were tested alone against the range of bacterial isolates from skin lesions. The wells were filled to the surface with a preparation of approximately 2 gms neat Surgihoney of the three potencies, diluted and emulsified in an equal volume of sterile water. Zone sizes were measured after 18-24 hours aerobic incubation (longer for Candida and Aspergillus spp., and anaerobically for Propionibacterium sp. And Bacteroides sp.)
Surgihoney product was warmed to 37° C. to liquefy it and 5 gms was mixed with 10 mL sterile deionised water. This dilution was regarded as the ‘neat’ substance for serial dilution. The British Society of Antimicrobial Chemotherapy (BSAC) method for performing minimum inhibitory concentrations (MIC's) and minimum bactericidal concentrations (MBC's) was used (Andrews J M. Determination of minimum inhibitory concentrations. J Antimicrob 372 Chemother 2001; 48(Supp 1): 5-16). The Surgihoney products were serially diluted in microtitre tray wells from neat to 1 in 1024. 75 μL of each honey dilution was added to each well in the strip of the microtitre tray. The neat concentration represented a concentration of 250 gm/L and the 1 in 2048 dilution, approximately 0.12 gm/L.
The test organisms were prepared by taking four morphologically identical colonies for each organism from pure culture to create a 0.5 McFarland density. This was further diluted 1:10.
All wells including controls were inoculated with 75 μL of the test isolate preparation. The well trays were incubated at 37° C. for 18 hours. The MIC was regarded as the most dilute well that showed no detectable turbidity.
The MIC well and those around the MIC well were sub-cultured on blood agar and incubated at 37° C. for 18 hours to determine the MBC. The MBC was the most dilute concentration which showed no growth after incubation.
The test organism inoculums was prepared by taking 0.1 mL of a 0.5 MacFarlane density of the test organism and inoculating this in 3 mL of nutrient broth. The test inoculums was divided into 3 separate bijous, a control and three test preparations to which were added 0.5 g of Surgihoney 1 (S1), Surgihoney 3 (S3) or Medihoney (MH). Colony counts of the inocula were determined by serial dilution 1:10 and plating 0.1 mL on a blood agar plate, repeated 3 times.
The test and control inocula were kept at 30° C. to simulate the temperature of a superficial skin lesion. Colony counts were performed as above in triplicate at time 0.5, 2, 4, 24, 48, 72 and 168 hours.
A terminal culture was performed by inoculating 0.1 ml of the original inoculums into nutrient broth to neutralise any residual effect of the Surgihoney and incubating for 72 hours at 37° C., before plating on blood agar to determine test organism survival.
The pilot comparative studies demonstrated that all the Surgihoney potencies had greater antimicrobial activity than any other honey tested including the medical grade honey, Medihoney. The inhibitory zones for S1 were larger than those produced by any other honey. Silver dressings produced some inhibitory effect beneath the dressing but there was no zone of inhibition as there was for Surgihoney. Iodine dressings produced a large zone of inhibition (approximately 70 mm) to Staphylococcus aureus, larger than S1 (36 mm) and equivalent to S3 (67 mm).
In the quantitative zone size testing, Surgihoney at all potencies produced an inhibitory zone in agar diffusion against all bacteria tested, both Gram positive and Gram negative bacteria including multiply antibiotic resistant bacteria, and fungal species. The zone size for each species increased with increasing Surgihoney potency preparations. Table 5. The inhibitory effect of Surgihoney was not dependant only on direct contact with the active agent as with the silver dressings, but diffused well beyond the well producing the extensive zones listed in Table 5.
Surgihoney demonstrated significant antimicrobial activity against all the isolates tested. MIC's and MBC's were very consistent amongst isolates of the same species whether the isolates were multidrug resistant or highly sensitive. Table 6 lists the MIC and MBC values for isolate species tested by dilution ratio and Table 7 shows the MIC and MBC's in grams per litre. The degree of potency rose with the grade of Surgihoney. The MBC for each isolate was close to the MIC within a single dilution in most cases.
Topical concentration of Surgihoney is estimated at approximately 500 gms/L. Surgihoney 1 MIC/MBC's for Staph. Aureus are 31 and 125 gms/L and Surgihoney 3 MIC/MBC's 0.12 and 0.24 gms/L respectively.
Surgihoney kills bacteria rapidly. Starting with a colony forming units per millilitre (cfu/mL) of approximately 105, cfu/mL numbers in the control rose steadily, whereas in the Surgihoney inocula the cfu/mL fell rapidly after contact with both potencies of Surgihoney. By 30 minutes cfu numbers had fallen 1000 fold in most cases for both S1 and S3 (
Surgihoney is natural honey which is also organic in the current sense of the word in that it has no agricultural additives or antimicrobial residues unlike much commercial honey for human consumption. It is not dependant on particular nectar sources, unlike honeys such as manuka which depends on a specific plant nectar source for its enhanced activity. The antimicrobial activity can be controlled in Surgihoney by the preparation process allowing the production of different grades with measured potency which is consistent.
This study has clearly demonstrated the efficacy of Surgihoney as a highly potent antimicrobial, active against all species of bacteria and fungi tested. In the preliminary pilot studies comparing Surgihoney with a variety of honeys sourced from around the world and with medical grade honey, Medihoney, Surgihoney demonstrated significantly greater antimicrobial efficacy. By comparison with the commonly used topical antiseptics silver and iodine, Surgihoney 3 produced an antimicrobial effect as great as iodine dressings and greater than silver dressings (Aquacel Ag) which was only effective at inhibiting bacteria in direct contact with the dressing.
MIC and MBC testing show that Surgihoney not only inhibits but also kills microbes at concentrations 10 to a 1000 fold below those that are likely to be achieved in topical treatment, estimated at 500 gms/L. The cidal activity of Surgihoney occurs at concentrations close to its inhibitory activity. There is therefore the potential for Surgihoney to be highly active in polymicrobial inhibition and eradication when applied topically.
The speed of cidal activity is shown by the time kill curves to be extremely rapid, within 30 minutes for Surgihoney 3 and within 2 hours for Surgihoney 1. This is the case for both Gram-positive and Gram-negative organisms, although enterococci appear slightly more resilient. Fungi, Candida spp. Aspergillus sp. also require higher concentrations and more prolonged exposure to inhibit growth and kill the organism.
These in vitro studies have demonstrated the potential of Surgihoney with high antimicrobial activity whose potency can be controlled.
These in vitro results support the clinical use of Surgihoney as a potent and non-toxic antimicrobial.
Staphylococcus
aureus (MSSA)
Staphylococcus
aureus (MRSA)
Streptococci Beta
Enterococcus spp
Escherichia coli
Klebsiella sp.
Pseudomonas
aeruginosa
Acinetobacter lwoffii
Bacteroides fragilis
Propionibacterium
acnes
Candida sp.
Aspergillus
fumigatus
Enterococcus
E. coli
E. coli ESBL
Kleb. pneumoniae
Pseud. aeruginosa
Candida albicans
Enterococcus
E. coli
E. coli ESBL
Kleb. pneumoniae
Pseud. aeruginosa
Candida albicans
10 g Surgihoney was dissolved in 10 ml of glycerol. 10 ml of paraffin oil was then added to a Rheometer (TA Instruments AR-G2) which had a Jacket Peltier and vane geometry attached. 1 ml of PGPR (Polyglycerol polyricinoleate) was then added. The rheometer was then started under the following conditions; Shear rate 2000 1/s, Temperature set at 37.5° C. After 2 minutes, 10 ml of Surgihoney-glycerol solution was added dropwise. Once a total of 10 minutes had elapsed the emulsion was transferred from the Jacket Peltier to a container.
Optical microscopy revealed that the emulsion contained reverse micelles which encapsulated Surgihoney. Such micelles can be observed in
Hydrogen peroxide stick tests (Purchased from Sigma Aldrich (Quantofix®)) were used to detect hydrogen peroxide in the emulsion. The tests were carried out before and after addition of water, and showed that before addition of water, the emulsion produced no hydrogen peroxide, and after water was added, the emulsion tested positive for hydrogen peroxide. A positive test was indicated by a colour change to blue.
Stability Test The emulsion maintained its capacity to generate hydrogen peroxide after storage at ambient conditions for at least four weeks.
The emulsion was added to a pump-action spray bottle and was found to be sprayable.
The effects of changing the Surgihoney emulsion preparation method described in Example 7, one parameter at a time, were investigated. The changes and their effects are summarised below.
i) Proportion of the Oil Phase to the Surgihoney-Glycerol Phase
Oil volumes greater than 10 ml, and less than 10 ml, were tested. The emulsion was found to be more stable when a lower volume of oil was used compared to the volume of the Surgihoney-glycerol phase. When the volume of the oil was less than 6 ml, the emulsion was found to separate by less than 3% in total volume over 72 hours. A volume of 4 ml allowed a separation of just 1.3% of the total volume over 72 hours. This stability is far greater than that of the method described in Example 7, which provided an emulsion with a separation of 9.4% of total volume over the same time period.
ii) Volume of PGPR
PGPR volumes up to 4 ml, and less than 1 ml, were tested. The emulsion was more stable when a higher amount of PGPR was used. At a volume of 4 ml, PGPR provided greater stability than with use of lower volumes, and far greater stability than that of the emulsion described in Example 7.
iii) Shear Rate
Shear rates from 1000 1/s to 3000 1/s were tested. The emulsion was more stable when a higher shear rate was applied. A shear rate of 3000 1/s produced the most stable emulsion. Separation of only 4.6% of the total volume over 72 hours was observed for emulsion prepared at this shear rate, compared with a separation volume of 9.4% of the total volume over the same time period for emulsion prepared as described in Example 7.
iv) Temperature
Temperatures from 20° C. to 40° C. were tested. There was no noticeable trend regard the stability of the emulsions as temperature was increased. However a temperature of 40° C. produced the most stable emulsion. Separation of only 3.1% of the total volume over 72 hours was observed for this emulsion.
v) Length of Shear
Shear times of 20 minutes and 30 minutes were tested, in addition to that used in the preparation method described in Example 7. However, there was no significant difference produced by extending the shear time.
vi) Order of Reagent Addition
The effect of changing the order in which the reagents are added to the rheometer was tested. The effect of adding all of the components before starting the rheometer was compared with the effect of adding the Surgihoney-glycerol and oil components first, then adding the PGPR after 1-2 minutes. The most stable emulsion was formed when the PGPR was added last. The resulting emulsion provided a separation volume of 2.8% of the total volume over 120 hours.
vii) Concentration of Surgihoney Dissolved in Glycerol
The following ratios of Surgihoney (g) to glycerol (ml) were tested: 1 g:1 ml; 0.5 g:1 ml; 2 g:1 ml. The ratio that produced the most stable emulsion was 1 g:1 ml, the same ratio used in the preparation method described in Example 7.
viii) Sodium Chloride
When sodium chloride is dissolved in the polar layer of the emulsion, it increases the polarity of this layer. It also forms electrostatic interactions with the lipid layer of the emulsion. The electrostatic interactions and increased polarity could improve stability and reduce coalescence. However, addition of sodium chloride (1 g, 2 g or 4 g) was not found to influence the stability of the emulsion.
The effects of the changes are summarised in the table below:
Surgihoney Emulsions with High Stability
The results from the changes described in Example 8 were used to design a further method of preparing Surgihoney emulsion. This method is described below.
10 g Surgihoney was dissolved in 10 ml of glycerol. 4, 6, 8, or 10 ml of Paraffin oil was then added to the rheometer (TA Instruments AR-G2) which had a Jacket Peltier and vane geometry attached. 10 ml of Surgihoney-glycerol solution was then added to the rheometer. The rheometer was then started under the following conditions; Shear rate 3000 1/s, Temperature 40° C., gap 4000 μm, Run time 10 minutes. After 1 minute 4 ml of PGPR (Polyglycerol polyricinoleate) was then added. Once a total of 10 minutes had elapsed the emulsion was transferred from the rheometer to a container.
All of the formulations were found to be highly stable, with a slight increase in stability observed as the volume of paraffin oil used was increased.
1.5 g of Surgihoney was dissolved in 1.5 ml of glycerol. 1 g of sodium alginate was then dissolved in the Surgihoney-glycerol solution. Next 10 ml of Paraffin oil was added to the Rheometer (TA Instruments AR-G2) which had a Jacket Peltier and vane geometry attached. 1 ml of PGPR (Polyglycerol polyricinoleate) was then added. The rheometer was then started under the following conditions; Shear rate 2000 1/s, Temperature set at 37.5° C., gap 4000 μm, Run time 10 minutes. After 2 minutes, 1.5 ml of the Surgihoney-alginate and glycerol solution was added to the rheometer. After 3 minutes 8 ml of calcium chloride solution was added dropwise to the rheometer. Once a total of 10 minutes had elapsed the emulsion was transferred from the Jacket Peltier to a container.
The method described in Example 10 uses water to dissociate calcium chloride into its ions. This could potentially activate the Surgihoney to produce hydrogen peroxide, and limit the stability of the cream formulation. However, we have appreciated that calcium chloride can be dissociated using non-aqueous solvents, such as ethanol or acetic acid. We have also appreciated that glycerol is able to bind to free water. This property allows water to be used to dissolve the alginate, provided sufficient glycerol is present to prevent premature release of hydrogen peroxide.
The method described below uses ethanol as a solvent for calcium chloride, and glycerol to bind free water in the alginate solution.
1 g of sodium alginate is dissolved in 15 ml water. Next 30 ml glycerol is added to the alginate solution and mixed. Then 30 g Surgihoney is then dissolved in the solution. 10 ml of Paraffin oil is then added to the rheometer (TA Instruments AR-G2) which has a Jacket Peltier and vane geometry attached. 10 ml of Surgihoney solution is then added to the rheometer. The rheometer is then started under the following conditions: Shear rate 3000 1/s, Temperature 40° C., gap 4000 μm, Run time 10 minutes. After 1 minute 4 ml of PGPR (Polyglycerol polyricinoleate) is added. After 2 minutes 8 ml of non-aqueous calcium chloride solution (1 M Calcium chloride in ethanol) is added dropwise to the rheometer. Once a total of 10 minutes has elapsed, the emulsion is transferred from the rheometer to a container.
Summary of emulsion formulations in Examples 7-11:
Optimised Formulation without Addition of Water
An emulsion was optimised in order to achieve greater stability whilst also attempting to keep viscosity as low as possible. The final formulation and the materials used to generate the emulsion can be seen in their percentage volume in Table 11.
Method 1 was used in order to achieve a stable emulsion using the materials from table 11.
Before addition of water to the emulsion, no reactive oxygen is produced. When water is added to the emulsion, reactive oxygen is produced. This is evidenced by a colour change on a hydrogen peroxide test strip.
The reverse micelles that are produced by the optimised formulation without the addition of water can be seen in
The spray that is produced by the optimised formulation without the addition of water created a jet like ejection (See
Formulation with Addition of Water
Small amounts of glycerol were added to the formulation. The amount of free water that can be added to the formulation is limited by the amount of glycerol present (1.7 g of glycerol needed to bind to 1 g of water). In order to make sure that reactive oxygen is not produced prematurely, a maximum of 2 mL of water was added to the formulations as the current volume of the emulsions being created only contain 5 mL of glycerol.
Method 2 is based upon method 1 and continues to use many of the parameters that were optimised previously. The main difference between method 1 and method 2 is that there is an additional step at the beginning. This step is to take into account the addition of free water and aims to stop the premature production of hydrogen peroxide ensuring that the free water is bound to the glycerol prior to the addition of Surgihoney to the system.
Two different techniques were used, as demonstrated in in
The rheometer (AR-G2 TA Instruments) was set to perform constant shear at rates of 100 and 1000 1/s. The temperature was fixed at 20° C. The samples were assessed about 24 hours after their formulation.
At lower shear rates it was found that the emulsions which contained water were less viscous than the emulsions which did not contain water, this is evident in
The rheometer (AR-G2 TA Instruments) was set to perform a temperature ramp of +2° C. per minute between 10 and 50° C., under a constant shear of 100 1/s.
The emulsions were created about 24 hours prior to testing. It was found that the control emulsion which contained no water was the most viscous, producing a viscosity of 0.5 Pa·s at 10° C. reducing to a viscosity of 0.07 Pa·s at 50° C. In comparison, Emulsion 2, which contained 2 mL of water, produced the least viscous emulsion with its viscosity at 10° C. being measured at 0.2 Pa·s and dropping to 0.06 Pa·s at 50° C. All three emulsions, as the temperature neared 50° C. produced similar viscosities.
In order for an assay to provide accurate results the level of hydrogen peroxide produced must fall within the range of the assay (no greater than 10 μM). In order to determine the dilution required for the Surgihoney to produce hydrogen peroxide within this range, values were taken at a number of dilutions. The assay used in this work was a fluorometric hydrogen peroxide assay produced by Sigma Aldrich (MAK165).
Surgihoney both from the tube and the sachet were allowed to incubate in water for a period of 30 minutes. The assay reagents were then added and incubated for a further 30 minutes before the relative fluorescence units were recorded. This experiment suggested that at dilutions of 1 g/L or less the level of hydrogen peroxide falls within the range of the assay.
If the concentration of Surgihoney in solution is set at a fixed concentration of 1 g/100 ml the amount of hydrogen peroxide produced in both Emulsions 1 and Emulsions 2 after 30 minutes incubation in water and a further 30 minute incubation in assay reagent, was significantly lower than that of the Surgihoney tube and sachet (See
This suggests that there will be a more controlled release over a longer time period in comparison to using the Surgihoney tube and sachet.
Samples with batch number “RO” contain no glucose oxidase.
Samples with batch number “RO1” contain 50 ppm glucose oxidase.
Samples with batch number “RO2” contain 1000 ppm glucose oxidase.
Non sterile base buffered saccharide solution.
Sterile base buffered saccharide solution
Non sterile base buffered RO1 saccharide solution.
Sterile base buffered RO1 saccharide solution
Non sterile base buffered RO2 saccharide solution.
Description Sterile base buffered RO2 saccharide solution
Non sterile base buffered saccharide solution.
Description Sterile base buffered saccharide solution
Non sterile base buffered RO1 saccharide solution.
Sterile base buffered RO1 saccharide solution
Non sterile base buffered RO2 saccharide solution.
Sterile base buffered RO2 saccharide solution
C. pH 7.04 buffered samples
Non sterile base buffered saccharide solution.
Sterile base buffered saccharide solution
Non sterile base buffered RO1 saccharide solution.
Sterile base buffered RO1 saccharide solution
Non sterile base buffered RO2 saccharide solution.
Sterile base buffered RO2 saccharide solution
MIC and MBC were assessed for the RO1 samples (containing 50 ppm glucose oxidase) and compared to Surgihoney™ (also containing 50 ppm glucose oxidase). See Andrews J. M. Journal of Antimicrobial Chemotherapy (2001) 48, suppl. S1, 5-16.
The results are shown in
The results show that, like Surgihoney, synthetic compositions containing glucose, glucose oxidase and fructose are able to inhibit microbial growth.
Out of all of synthetic compositions, the synthetic composition buffered at pH7.04 had the most effective MIC. Sterilised compositions were more effective than non-sterilised compositions, and the synthetic composition buffered at pH7.04 had the most effective MBC when compared to the other synthetic compositions and even when compared to Surgihoney.
The results show that, like Surgihoney, synthetic compositions containing glucose, glucose oxidase and fructose are able to inhibit microbial growth.
The synthetic compositions could replace the Surgihoney in the emulsion compositions exemplified in Examples 1 to 14, and also in Examples 16 to 18.
Methods may be modified in order to form emulsions containing smaller micelles. Smaller micelles may lead to an improvement in stability. The size of micelles may be reduced by using a high speed disperser/homogeniser, such as a IKA T 18 digital ULTRA-TURRAX with S 18 N-19 G element.
A generalised method to create emulsions with small micelles (typically with a range of 10-50 μm), is as follows:
1) Pre-mixing to disperse the surfactant (PGPR) in the oil phase (paraffin). The surfactant is added to the oil, the homogeniser (set at 10,000 RPM) is then allowed to run for 2 minutes to ensure adequate dispersion.
2) The Surgihoney (this could include a pre-mix of Surgihoney+Solvent e.g. glycerol) is then slowly added at a rate of 1 ml per 30 seconds to the oil phase.
3) Once Surgihoney is added, the homogeniser is allowed to run until a total elapsed time of 10 minutes (not including pre-mix steps) has been reached.
4) The final emulsion is then transferred from the glass beaker into a sealed tube for storage.
0.5% of xanthan gum was added to glycerol at ambient temperature, then heated and moderately mixed to 85° C. 0.1% of magnesium sulfate heptahydrate was then added to the hot mixture and mixed until complete dissolution. The mixing is continued without heating until the mixture reaches 25° C. At this point SurgihoneyRO was added and mixed in a ratio of 2 g SurgihoneyRO: 1.5 ml mixture. Creams of 20 ml were prepared. 10 ml paraffin oil and 2% PGPR (0.4 ml) were added to a beaker and mixed for 1 minute at 10,000 rpm using an IKA ULTRA-TURRAX homogenizer. 10 ml of SurgihoneyRO/solvent/xanthan gum/magnesium sulfate heptahydrate solution was added dropwise for 4 minutes while mixing. The cream was mixed for an extra 5 minutes to reach 10 minutes mixing in total.
SurgihoneyRO: Paraffin emulsions were prepared in ratios of 30:70, 40:60, 50:50 and 60:40. Paraffin oil and 0.5%, 1% and 2% PGPR were added to a beaker and mixed for 1 minute at 10,000 using an IKA ULTRA-TURRAX homogenizer (Sigma Aldrich Co Ltd, UK). SurgihoneyRO at the corresponding ratio was added dropwise at a rate of 30 seconds per ml while mixing. The emulsion was continued to be mixed until 10 minutes of total mixing time had been achieved.
Emulsions were created using a T18 Ultra Turrax® disperser (IKA, UK). An AR-G2 Rheometer (TA Instruments, UK) was used to determine the viscosity of the emulsions. Droplet size was characterised by use of a Malvern 3000 Mastersizer (Malvern Instruments, UK). The presence of hydrogen peroxide was detected using Quantofix test sticks (Sigma Aldrich, UK) as well as a fluorescence hydrogen peroxide assay (Sigma Aldrich, UK).
The formulation also maintained its capacity to generate ROS when stored under ambient conditions (21° C.).
| Number | Date | Country | Kind |
|---|---|---|---|
| 1619312.0 | Nov 2016 | GB | national |
| 1711095.8 | Jul 2017 | GB | national |
| 1718490.4 | Nov 2017 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2017/053441 | 11/15/2017 | WO | 00 |
