Stabilised hypohalous acid solutions

Abstract

The present invention relates to a stabilised solution or formulations (a liquid or a thixotropic gel) of hypohalous acid, such as hypochlorous acid (HOCI), as well as methods for their production and use. The stabilised solution or formulation comprises the hypohalous acid and a stabilising amount of dissolved inorganic carbon (DIC) incorporated in the form of carbonic acid or bicarbonate of an alkali or alkaline earth metal.

Description

[0001] STABILISED HYPOHALOUS ACID SOLUTIONS TECHNICAL FIELD

[0002] The present invention relates to stabilised solutions and formulations of hypohalous acid, such as hypochlorous acid (HOCI), as well as methods for their production and use. The solution finds use for cleaning and / or disinfecting surfaces, food such as fruit, vegetables and crops, or mammalian tissues (including wounds). The solutions further find use in the preservation of agricultural products and cut flowers.

[0003] BACKGROUND

[0004] Hypochlorous acid is an oxidant and biocide that is produced by the human body’s natural immune system to fight infection. Hypochlorous acid is generated as the final step of the Oxidative Burst Pathway, with large quantities of hypochlorous acid being released into the phagocytic vesicles to destroy the invading microorganisms. It is considered that hypochlorous acid exerts its biocidal effect by attacking the surface and plasma membrane proteins, impairing transport of solutes and the salt balance of bacterial cells (Pieterson et al., Water SA, 22(1): 43-48 (1996)). Escherichia coli exposed to hypochlorous acid lose viability in less than 100 ms due to inactivation of many vital systems (Fair et al., J. Am. Water Works Assoc. 1051-1061 (1940)). Hypochlorous acid at 2.6 ppm caused 100% growth inhibition of E. coli in dilute bacterial suspensions in about 5 minutes (Chesney et al., J. Bacteriol. 2131-2135 (1996)). According to Chemistry of Water Treatment (2ndEdition), Samuel D. Faust and Osman M. Aly (1998), 100% kill in 5 minutes requires only 0.08 ppm for A. aerogenes, 0.06 ppm for S. typhosa. 0.05 ppm for S. dysenteriae, and 0.03 ppm for E. coli.

[0005] Although hypochlorous acid is biocidal to microorganisms, it is not significantly toxic to human or animal cells, at least partly because human and animal cells have extensive and highly effective defence mechanisms known as the Antioxidant Defence System (ADS). Hypohalous acid has a wide range of applications where it is important to control microbial contamination, such as for the care and management of wounds, disinfection of hard surfaces such as medical or dental equipment, food safety and processing, water treatment, as well as other industrial and agricultural applications.

[0006] One limitation associated with solutions of hypochlorous acid is their stability, which has limited much of the commercial use to those situations where the solution can be made on site for relatively immediate use. Existing alternatives include Dakin’s solution for wound care, which is a diluted sodium hypochlorite solution (0.5%) prepared by mixing sodium hypochlorite (5.25%), sodium bicarbonate / carbonate (1%), and clean tap water. However, Dakin’s solution has a high pH, and thus causes pain and burning in wound treatment along with rashes, itching, swelling, hives, and / or blisters. Further, Dakin’s solution is unstable and unsuitable for clinical use at lower pH’s (< 8.5).

[0007] Another alternative is the Microcyn™ solution. While Microcyn™ has a 2-year shelf life, it suffers from a limited level of available free chlorine (AFC) of about 80 ppm (pH of 7.4), and lower percent of hypochlorous acid, which may limit its biocidal effectiveness. EcaFlo™ is available for hard surface disinfection. This solution contains equimolar amounts of hypochlorite and hypochlorous acid in addition to high sodium chloride content. The pH of the solution is around 7.5 and the solution has an AFC content of approximately 460 ppm. The solution has a relatively short shelf life of 30 days.

[0008] To address the unsatisfied need for a hypohalous acid solution that has a high AFC content, has sufficient stability and / or other properties required to be commercially useful in medical and other commercial settings, and is not irritating or harmful to humans, Panicheva et al. (WO 2012 / 129161) have proposed a stabilised solution or formulation packaged in a container for storage or sale, comprising hypochlorous acid and a stabilising amount of dissolved inorganic carbon (DIC) incorporated in the form of a bicarbonate or carbonate of an alkali or alkaline earth metal, wherein the solution or formulation has an available free chlorine (AFC) content of from about 10 to about 10,000 parts per million, a pH of from about 4.0 to 7.0, a DIC-to-AFC molar ratio of from 5:1 to 1 :5, and wherein the container is minimally permeable to CO2 or O2.

[0009] According to Panicheva et al. (WO 2012 / 129161), the method for obtaining the stabilised solution or formulation involves incorporating the DIC (e.g., in the form of carbonate or bicarbonate) by adding it to an electrolyte for electrochemical treatment, or incorporating the DIC (e.g., in the form of carbonate or bicarbonate) by directly adding it to an electrolysed solution comprising hypohalous acid (e.g., HOCI).

[0010] More in detail, Panicheva et al. (WO 2012 / 129161) teach that the stabilised hypochlorous acid solutions (e.g., solutions of greater than 90%, 95%, or 97% HOCI) may be obtained by electrolysis of a saline solution as described in U.S. Patent 7,276,255 or can be prepared by any suitable method or apparatus by incorporating the bicarbonate or carbonate into the dry electrolyte or the solution for electrolysis. The carbonate or bicarbonate can be added to the dry electrolyte in accordance with the desired AFC content of the resulting solution. Hypochlorous acid solutions may be prepared by passing saline solution containing the carbonate / bicarbonate over coated titanium electrodes separated by a semi-permeable ceramic membrane at a current of about 6 to 9 Amps. Electrochemical treatment of saline is described, for example, in U.S. Patent 7,303,660, U.S. Patent 7,828,942, and U.S. Patent 7,897,023.

[0011] When dissolved in water, a bicarbonate or carbonate of an alkali or alkaline earth metal imparts an alkaline pH to the solution. It will therefore be apparent to those skilled in the art that, in order to obtain a stabilised solution or formulation comprising hypochlorous acid and a stabilising amount of dissolved inorganic carbon (DIC) incorporated in the form of a bicarbonate or carbonate of an alkali or alkaline earth metal, and having a pH of from about 4.0 to 7.0, a particular electrolysis apparatus is required, comprising one or more electrolytic cells, each of which comprises an anode, a cathode and a separator (diaphragm or membrane) capable of avoiding mixing between the solution treated at the anode and the one treated at the cathode. When subjected to electrolytic treatment on the anode side of the just described electrolytic cell, the saline solution (i.e., a solution containing an alkali or alkaline earth halogenide) entering the cell is converted into a solution containing the corresponding hypohalous acid. If the saline solution originally has an alkaline pH (due to the presence of a bicarbonate or carbonate of an alkaline or alkaline earth metal), depending on the residence time of the solution in the electrolytic cell and the electric current used, the electrolytic treatment on the anode side of the electrolytic cell above described may allow to lower the solution pH up to acidic values (i.e. lower than 7), and thus to obtain a solution or formulation with the characteristics described by Panicheva et al. (WO 2012 / 129161). Unfortunately, this can only be obtained by using an electrolysis apparatus in which the anode and cathode compartments are kept separated by using a diaphragm or a membrane.

[0012] Based on the above, there is still an unmet need for a simple way to prepare a hypohalous acid solution that has a high AFC content, has sufficient stability and / or other properties required to be commercially useful in medical and other commercial settings, and is not irritating or harmful to humans. The claimed invention meets these and other objectives.

[0013] Throughout this specification, unless the context requires otherwise, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0014] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention, as it existed before the priority date of each claim of this specification.

[0015] SUMMARY OF THE INVENTION

[0016] The present invention relates to a stabilised hypohalous acid solution or formulations thereof, which may be conveniently packaged for sale, or stored for later use on demand. The invention further relates to methods of making the stabilised hypohalous acid solution or formulation thereof, as well as methods of use for disinfecting mammalian tissue, including wounds and burns, disinfecting or cleansing hard surfaces, treating (e.g., preserving and / or disinfecting) food products or cut flowers, among other uses. In a first aspect, the invention provides a stabilised solution or formulation packaged in a container for storage or sale, comprising hypochlorous acid and a stabilising amount of dissolved inorganic carbon (DIC) incorporated in the form of carbonic acid or as a bicarbonate of an alkali or alkaline earth metal, wherein the solution or formulation has an available free chlorine (AFC) content of from about 10 to about 10,000 parts per million, a pH of from about 4.0 to 6.75, a DIC-to-AFC molar ratio of from 10:1 to 5:1 , and wherein the container is minimally permeable to CO2 or O2.

[0017] In another aspect, the present invention provides a method for preparing the stabilised solution or formulation according to the first aspect of the invention, comprising: incorporating the DIC into the solution or formulation, in amounts sufficient to stabilise the solution or formulation for at least six months.

[0018] In a further aspect, the present invention provides a method for disinfecting or treating a mammalian tissue, the method comprising applying the solution or formulation to a mammalian tissue in need of disinfection or treatment.

[0019] In another aspect, the present invention provides a method for disinfecting or cleansing a hard surface comprising applying the stabilised solution or formulation according to the first aspect of the invention to the hard surface, and optionally, wherein the hard surface comprises porcelain, glass, steel, iron, ceramic or polymeric material.

[0020] In a further aspect, the present invention provides a method of treating a food product comprising the application of the stabilised solution or formulation according to the first aspect of the invention to the food product, and optionally, wherein the solution is applied as a mist, fog, spray, or ice.

[0021] Also disclosed herein is a stabilised hypohalous acid solution. The solution incorporates a stabilising amount of dissolved inorganic carbon (DIC), which can be in the form of carbonic acid or as a bicarbonate of an alkali or alkaline earth metal. The solution may have an available free halide (AFC) content of from about 10 to about 10,000 parts per million, and a pH of from about 4.0 to about 6.75. For example, in certain embodiments, the solution has a pH of from about 6.1 to about 6.75. In certain embodiments, the solution contains hypochlorous acid, and is prepared by electrolysis of saline. The solution is stabilised, as determined by its limited change in pH and / or AFC over time, for at least one month, but in various embodiments, the solution is stabilised for at least six months, at least one year, or more.

[0022] In certain embodiments, dissolved inorganic carbon is incorporated into the solution at a level of about 10:1 to about 5:1 molar ratio relative to the AFC content. For example, dissolved inorganic carbon may be added at a level of about 6:1 , about 6.5:1 , or about 7:1 or at a larger molar ratio relative to the AFC content. For example, the solution may comprise HOCI produced by electrolysis of saline, and the solution may have an AFC content of from about 100 to about 500 parts per million, a pH in the range of about 5 to about 6.75, a salinity of about 0.02% to about 1.0%, and an amount of dissolved inorganic carbon in the range of about 700 mg / L to about 5000 mg / L. In some embodiments, the salinity of the solution does not impact the amount of dissolved inorganic carbon needed for solution stabilisation. In certain embodiments, the HOCI solution is formulated as a hydrogel.

[0023] Also disclosed herein is a method for preparing the stabilised hypohalous acid solution. The method involves incorporating the dissolved inorganic carbon (e.g., in the form of carbonic acid or as a bicarbonate of an alkali or alkaline earth metal) by addition of carbon dioxide to a solution comprising an alkali or alkaline earth hypohalite (e.g., NaOCI). For example, an electrolysed solution or other hypohalite solution may be diluted with carbonated water (i.e., water that has been infused with carbon dioxide gas under pressure) or with an aqueous solution comprising carbon dioxide, or even directly infused with gaseous carbon dioxide. In other embodiments, the electrolysed solution or other hypohalite solution may be diluted (to have the desired AFC content) and then added with carbonated water or directly infused with gaseous carbon dioxide. The latter is an effective method for production of low ionic strength hypohalous acid solutions, especially for hydrogel formulations.

[0024] Also disclosed herein are methods of disinfecting, cleansing, or treating a mammalian tissue, such as a wound, burn, or dermatosis, or methods of sanitising, disinfecting or cleansing a hard surface, or methods for treating or preserving a food or agricultural product or cut flowers. Due to the stability of the hypohalous acid solutions and formulations, such methods need not be performed proximately to the production of the biocidal solution. Other embodiments disclosed herein relate to a method for treating a skin condition, including dermatosis, rosacea, skin infection, skin allergy, psoriasis, or acne. In such embodiments, the HOCI may be formulated as a hydrogel.

[0025] Other aspects and embodiments of the invention will be apparent from the following detailed description of the invention.

[0026] DESCRIPTION OF THE FIGURES

[0027] Figure 1 shows the relative percentage of the HOCI and NaOCI species present in a free chlorine aqueous solution at a temperature of 20DC and 0.1 M ionic strength, as a function of pH (Dissociation of hypochlorous acid, in White’s Handbook of Chlorination and Alternative Disinfectants (5thedition), Black & Veatch Corporation, 2010).

[0028] Figures 2A and 2B show the change in AFC and pH over storage time of bottled aqueous solutions of free chlorine (produced by electrochemical treatment of a NaCI solution), whose pH was initially adjusted at about 7 with hydrochloric acid; different aliquots of the same solution were bottled in HDPE containers, stored at 40°C to accelerate the deterioration of the solution and kept unopened until measurement. The data shown are averages of three values; also shown is the linear regression (solid line) with 95% prediction intervals (broken lines).

[0029] Figures 3A and 3B show the change in AFC and pH over storage time of aqueous solutions of free chlorine (produced by electrochemical treatment of a NaCI solution), whose pH was initially adjusted at about 6.7 by direct infusion with gaseous carbon dioxide; different aliquots of the same solution were bottled in HDPE containers and stored at room temperature. Bottles were stored at 40°C to accelerate the deterioration of the solution and kept unopened until measurement; the data shown are averages of three values, along with the non-linear regression (solid line) with 95% prediction intervals (broken lines). DETAILED DESCRIPTION

[0030] The present invention provides a stabilised hypohalous acid solution or formulation thereof, which may be conveniently packaged for sale, or stored for later use on demand. The invention further provides methods of making the stabilised hypohalous acid solution, as well as methods of use for disinfecting mammalian tissue, including wounds and bums, disinfecting or cleansing surfaces, or treating or preserving food products or cut flowers, among other uses.

[0031] In one aspect, the invention provides a stabilised hypohalous acid solution or formulation thereof. The solution incorporates a stabilising amount of dissolved inorganic carbon (DIC), such as carbonic acid or a bicarbonate of an alkali or alkaline earth metal. The solution may have an available free chlorine (AFC) content of from about 10 to about 10,000 parts per million, and a pH of from about 4.0 to about 6.75. In certain embodiments, the solution contains hypochlorous acid, and is prepared by electrolysis of saline. The solution is stabilised, as determined by its change in pH and / or AFC over time, for at least one month, but in various embodiments, the solution is stabilised for at least six months, at least one year, or more.

[0032] While the solution or formulation comprising hypohalous acid may be produced chemically in accordance with some embodiments (e.g., by acidification of hypohalite), the hypohalous acid may also be produced electrochemically. The hypohalite solution may be generated by electrolysis of a halide salt, such as sodium chloride, and may comprise a mixture of oxidising species such as predominantly sodium hypochlorite and hypochlorous acid. Hypochlorous acid and hypochlorite are in equilibrium and the position of the equilibrium is determined predominantly by the pH (that is, pH affects the concentration of each component). An electrolysed sodium chloride solution with a pH of 8.8 to 10.0 has a purity of about > 95% sodium hypochlorite (see Figure 1); by reducing the pH to less alkaline values, the available free chlorine content can be converted into the more effective hypochlorous acid form. Thus, the pH-adjusted solution may have a pH of from about 4.0 to about 7.5, but in certain embodiments has a pH of from about 4.4 to about 6.75, or a pH of from about 5 to about 6.75, or a pH of from about 5.4 to about 6.4, or a pH of from about 6.0 to about 6.4. At a pH lower than 6.2 the solution will contain mostly (> 95%) hypochlorous acid with respect to hypochlorite (see again Figure 1).

[0033] To reduce the pH of a hypohalite solution having originally an alkaline pH (e.g. a pH comprised between 8.8 to 10.0) and convert the hypohalite into the more effective hypohalous acid form, any suitable acid that does not react with the hypohalite can be used; for example, the following acids may be considered: hydrochloric acid (HCI), sulphuric acid (H2SO4), chloric acid (HCIO3), perchloric acid (HCIO4), nitric acid (HNO3), phosphoric acid (H3PO4), acetic acid (CH3COOH), carbonic acid (H2CO3), boric acid (H3BO3).

[0034] While the final solution may comprise or consist essentially of hypochlorous acid as the active agent, in some embodiments it may contain other hypohalous acids (e.g., HOBr, or mixture thereof). In some embodiments, the solution contains other oxidising or radical producing species such as a hypohalite (e.g., hypochlorite), hydroxide, H2O2 and O3, among others.

[0035] The biocidal activity of the solution can be expressed in terms of available free chlorine or AFC. While the invention is applicable to an AFC range of from about 10 to about 10,000 ppm (or to about 5,000 ppm), in certain embodiments, the solution has a relatively high AFC content and is suitable for use with mammalian tissues or agricultural products. For example, the solution may have an AFC content of from about 100 to 1,000 ppm, or 100 to 500 ppm, or about 150 to about 250 ppm. Other AFC levels may be employed and may be selected based upon the intended application. For example, without any limitation, for surface disinfection the AFC may be in the range of about 140 to about 2,000 ppm, or about 400 to about 1 ,000 ppm.

[0036] The solution comprises a stabilising amount of DIC, which is added as carbon dioxide; by reacting with the excess alkalinity, the DIC may finally be present as a bicarbonate or carbonate of alkali or alkaline earth metal, such as, for example, sodium, potassium, calcium, or magnesium.

[0037] The DIC is incorporated at a “stabilising amount”, which can be determined with reference to the change in the pH or AFC content of the solution over time. Generally, the solution is considered stabilised if the amount of AFC does not drop below about 60% of the initial value over a period of about 6 months. In certain embodiments, the AFC content is stabilised for at least one year from the production date of the solution. The solution should be stored at 25°C or at 20°C or less for greater stability (i.e., 25°C and 20DC are the reference temperatures for determination of stability). For stability testing, solutions are packaged in FIDPE or PET bottles, stored in the dark and kept unopened. Accelerated tests can be performed by storing the solution at a higher temperature, and the shelf-life predicted from accelerated data by extrapolation; for example, storing the solution at 15 °C above normal storage conditions (storage conditions for Australia are considered to be the temperatures of 25 - 30 °C), a time period of 3 months gives a possible shelf-life prediction of 18 months (TGA instructions for disinfectant testing, version 2.1 , March 2020 - Australian Government, Department of Health, Therapeutic Goods Administration).

[0038] The stabilising amount of DIC can be determined with reference to the final pH of the solution. For example, in certain embodiments, the stabilising amount of DIC is incorporated into the hypohalite solution in such a way as to lower the pH of the solution to 6.75 or less.

[0039] For example, an electrolysed solution or other hypohalite solution may be diluted with carbonated water (i.e., water that has been infused with carbon dioxide gas under pressure) or diluted with an aqueous solution comprising carbon dioxide, or even directly infused with carbon dioxide gas under pressure. In other embodiments, the electrolysed solution or other hypohalite solution may be diluted to the desired AFC content and then added with carbonated water or directly infused with carbon dioxide gas under pressure. The latter is an effective method for production of low ionic strength hypohalous acid solutions, especially for hydrogel formulations.

[0040] Without being bound by theory, dissolved inorganic carbon (DIC, which generally includes carbonates, bicarbonates, carbonic acid and dissolved CO2) provides some buffering capacity in the pH range targeted by the solutions and compositions described herein. Nevertheless, these solutions are effectively stabilised due to, at least in part, free radical scavenging ability of DIC to thereby slow down the decomposition of HOCI. Further still, solutions prepared by electrochemically treating a sodium chloride solution (as opposed to sodium hypochlorite solutions obtained by diluting a commercial sodium hypochlorite solution) have distinct properties, and the stabilising effect obtained by adding DIC can be distinct.

[0041] In some embodiments, the addition of DIC provides enhanced biocidal effectiveness for treating microorganism or biofilms, especially in the presence of high organic load.

[0042] While the hypohalous acid solution may be in the form of a liquid, the solution may take the form of a cream, a thixotropic gel (e.g. silicate-based gel), and / or foam by the addition of conventional ingredients known in the art. For example, topical formulations of electrochemical solutions are disclosed in US 2005 / 0196462, which is hereby incorporated by reference in its entirety. In these embodiments, the formulation is better contained around the application site by limiting solution run-off. Further, convenient applicators for creams, foams, and the like are known, and may be used in accordance with the present invention. Since the solutions of the invention provide the potential for low conductivity, even with relatively high AFC content, and at “skin- friendly” pH levels, the solutions of the invention are particularly suitable for hydrogel formulations.

[0043] In certain embodiments employing hydrogel formulations, the composition has an AFC content of greater than about 150 ppm, greater than about 200 ppm, greater than about 250 ppm, greater than about 300 ppm, or greater than about 400 ppm. Further, the formulation may have a conductivity of from about 0.3 mS / cm to about 12 mS / cm, such as from about 0.5 mS / cm to about 10 mS / cm in some embodiments. Further, hydrogel formulations in some embodiments have a pH of from about 5 to about 7, or from about 6 to about 6.5 in other embodiments. The hydrogels may be prepared from silicate- based carriers, such as sodium magnesium fluorosilicate (e.g., from about 0.5% to about 5%), and may employ an additional buffer for targeting the pH . An exemplary buffer is phosphoric acid.

[0044] The stabilised solutions may be packaged for storage or sale, using any suitable container, such as any suitable plastic or glass bottles, or bags (e.g., plastic bags), tubes, or cans (e.g., spray or aerosol). In certain embodiments, the packaging material has minimal gas permeability, including by species such as CO2 and O2. The containers may be transparent, or opaque so that they are minimally penetrable by light, and may be of any unit volume, such as about 50 ml_, about 100 ml_, about 125 ml_, about 250 ml_, about 0.5 litre, about 1 litre, about 5 litres, about 10 litres, or greater.

[0045] The hypochlorous acid solution of the invention may also be hypertonic, hypotonic, or isotonic with respect to physiological fluids (blood, plasma, tears, etc.). Alternatively, the solution may contain varying levels of salinity, such as from 0.01 to about 2.0%. Generally, the solution contains from about 0.02% to about 0.9% w / v NaCI when intended for use in medicine. In some embodiments, the solution may be a normal saline solution (about 0.91% w / v NaCI). In some embodiments, the solution may contain from about 0.01 to 2.0% w / v of one or more salts, such as a halide salt, e.g. NaCI, KCI, or a mixture of salts or halide salts. The salt or halide salt may be a salt of an alkali metal or alkaline earth metal, such as sodium, potassium, calcium, or magnesium. In certain embodiments, the electrolysed solution is generated using a mixture of physiologically balanced salts, as disclosed in U.S. Patent 6,426,066, which is hereby incorporated by reference in its entirety. Such salts may include potassium halides (e.g., KCI) and magnesium halides (e.g., MgC ).

[0046] For example, an electrolysed solution or other hypohalite solution may be diluted with carbonated water or an aqueous solution comprising dissolved inorganic carbon in the form of carbon dioxide. In other embodiments, the diluted hypohalite solution (e.g., having the desired AFC content) is added to containers and then directly infused with carbon dioxide gas under pressure. The latter is an effective method for production of low ionic strength hypohalous acid solutions, especially for hydrogel formulations.

[0047] Still other aspects of the invention provide methods of disinfecting or cleansing a mammalian tissue, such as a wound or burn, or disinfecting or cleansing a hard surface, or for treating or preserving a food product or cut flowers. Due to the stability of the hypohalous acid solutions, such methods need not be performed proximately to the production of the biocidal solution, and the solution may be prepared well in advance of its use.

[0048] The solutions and formulations of the invention may be used as sterilising, disinfecting and biocidal solutions for human and animal care. The solutions are non-hazardous, non-irritating, non-sensitising to the skin, non-irritating to the eyes, not harmful if swallowed, and show no evidence of mutagenic activity. For example, the method of the invention provides for moistening, lubricating, irrigating, cleaning, deodorising, disinfecting, or debriding a wound by rinsing, washing or immersing the wound, with or in, the stabilised hypohalous acid solutions, or by applying the solution to the wound and / or wound dressing. The wound may or may not be infected, and thus the method of the invention is useful for treating infected wounds and useful for preventing infection of uninfected wounds.

[0049] In one aspect, the invention provides a convenient means for wound care and management and may be used in combination with the apparatus and methods described in U.S. 2010 / 030132, which is hereby incorporated by reference in its entirety. For example, the method may comprise supplying the stabilised solution to a wound site by one or more of soak, scrub, pulsed lavage, hydrosurgery, and ultrasound to effectively debride and disinfect a wound or tissue. The solution may be delivered before, during and / or after negative pressure wound therapy to promote proper wound healing physiology. In these embodiments, the method may employ a wound dressing for coordinating debridement by infusion of hypochlorous acid with negative pressure therapy. Thus, the invention may be used in combination with a wound treatment apparatus and / or wound dressing.

[0050] For example, in certain embodiments, the invention allows for an initial stabilised hypochlorous acid solution soak and / or scrub to both debride and disinfect the wound or tissue, followed by the application of negative pressure to the wound or tissue using the stabilised hypochlorous acid solution as an irrigating agent to control wound bioburden, remove excess exudate, and promote formation of granulation tissue. Optionally, the method also involves seamless transition to the stabilised hypohalous acid solution infusion (e.g., active or passive infusion without negative pressure). Such seamless transition can be effected via a wound dressing which allows for controlled infusion of stabilised hypochlorous acid solution with controlled vacuum source. In these embodiments, continued cell proliferation and regeneration continues without disruption of the wound bed, once the endpoints of negative pressure therapy have been obtained.

[0051] In certain embodiments of the invention, the wound needing care is a stage l-IV pressure ulcer, stasis ulcer, diabetic ulcer, post-surgical wound, burn, cut, abrasion, or a minor irritation of the skin. In certain embodiments, the wound is rinsed, washed, or immersed in the solution periodically over at least two weeks, but treatment may continue periodically for over about 4 weeks, about 9 weeks, or more. The wound, in some embodiments, is rinsed with the solution at least once a week, but may be treated with the solution at least twice a week, or more frequently.

[0052] While the stabilised hypohalous acid solution may be delivered to the wound at room temperature, the solution may alternatively be heated, for example, to body temperature or about body temperature. In this embodiment, the solution is comfortable and soothing for the patient, and is more effective.

[0053] In some embodiments, the invention provides a method for treating an infected or colonised wound, tissue, surgical cavity, or bone, and a method for reducing wound bioburden. The treatment solution in accordance with the invention, as already described, is generally effective for killing or inactivating a broad spectrum of bacterial, fungal, and viral pathogens, including S. aureus, P. aeruginosa, E. coli, Enterococcus spp., C. difficile, and Candida spp.. The solution does not produce resistant species, making the methods desirable over the delivery of traditional antibiotics.

[0054] In another aspect, the solution of the invention is particularly suitable for use in conjunction with stem cell and growth factor therapy, including the use of genetically engineered cells and engineered tissue and allografts and organs for transplant in various treatments. Using the stabilised hypohalous acid solution of the invention to disinfect tissue before, during or after addition of cells or growth factors, maintains the viability of the cells and integrity of the growth factors, while killing the unwanted microbes.

[0055] In certain embodiments, the solution or formulation thereof is applied for the control of inflammation, including an inflammatory reaction or hyper-inflammation of the skin. For example, the solution or formulation thereof may be applied for use in a method as described in U.S. 2007 / 0196357 or U.S. 2010 / 0285151, which are hereby incorporated by reference. In certain embodiments, the solution or composition of the invention is applied (e.g., to an affected area) for treatment of a patient having a dermatosis, atopic dermatitis, skin allergy, rosacea, psoriasis, or acne, among others. In such embodiments, the solution may be formulated as a hydrogel, for example, as described elsewhere herein. In certain embodiments, this invention may be used against microbes on surfaces because of its fast activity against bacterial spores, fungi, and other resistant microorganisms. Because of its effectiveness and the speed at which it acts, the invention meets a substantial public health need, and one that is not adequately addressed by current commonly used antimicrobial agents. Accordingly, application of the solution to various surfaces and materials is useful to control microbial contamination, not only for the care and management of wounds, but for disinfecting hard surfaces such as medical or dental equipment, preserving and decontaminating food products, water treatment, as well as other industrial and agricultural applications. In certain embodiments, the solution or composition of the invention is applied to crops (pre- or post-harvest) or cut flowers for their preservation and / or for improving the overall quality of the product. In some embodiments, the solution is potassium based and has one or more utilities (e.g., methods of use) as disclosed in PCT / US2011 / 43590, which is hereby incorporated by reference in its entirety.

[0056] In various embodiments, including the treatment of food, agricultural products, and surfaces, the solution can be applied as a mist, fog, spray, or ice.

[0057] Killing, inactivating, or otherwise reducing the active population of bacterial spores and fungi on surfaces is particularly difficult. Bacterial spores have a unique chemical composition of spore layers that make them more resistant than vegetative bacteria to the antimicrobial effects of chemical and physical agents. Likewise, the unique chemical composition of fungal cells, especially mould spores, makes them more resistant to chemical and physical agents than other microorganisms. This resistance can be particularly troublesome when the spores or fungi are located on surfaces such as food, food contact sites, ware, hospitals and veterinary facilities, surgical implements, and hospital and surgical linens and garments.

[0058] Control of the mould Chaetomium funicola, and of bacterial spore-forming microorganisms of the Bacillus species, can be especially important during food packaging, particularly during cold or hot aseptic filling of food and beverage products.

[0059] Microorganisms of the Bacillus species include Bacillus cereus, Bacillus mycoides, Bacillus subtilis, Bacillus anthracis, and Bacillus thuringiensis. These latter microorganisms share many phenotypical properties, have a high level of chromosomal sequence similarity, and are known enterotoxin producers. Bacillus cereus is one of the most problematic because it has been identified as possessing increased resistance to germicidal chemicals used to decontaminate environmental surfaces.

[0060] As used herein, the term “surface” refers to both hard and soft surfaces and includes, but are not limited to, tile grout, plaster, drywall, ceramic, cement, clay, bricks, stucco, plastic, wallpaper, fabric, tiles, cement and vinyl flooring, heating and / or cooling fins, filters, vanes, baffles, vents, crevices in walls or ceilings, paper and wood products such as lumber, paper, and cardboard, woven products such as blankets, clothing, carpets, drapery and the like. The term surface also includes human surfaces, animal surfaces, military equipment, transportation equipment, children’s items, plant surfaces, seeds, outdoor surfaces, soft surfaces, air, wounds, and medical instruments, and the like.

[0061] EXAMPLES

[0062] Example 1 : Solutions of free chlorine with neutral pH

[0063] Figures 2A and 2B show averages of three AFC and pH measurements for aqueous solutions of free chlorine (AFC « 350 ppm, initial pH » 9.7) produced by electrochemical treatment of a diluted saline, and then pH adjusted to about 7 with hydrochloric acid. Several aliquots of the same solution were bottled in HDPE bottles, stored at 40°C to accelerate the deterioration of the solution, and kept unopened until measurement. As shown, both the pH and AFC content were not stabilised over the long term. For example, the solutions were not stabilised for more than about one month.

[0064] Example 2: Stabilised solutions of free chlorine containing dissolved inorganic carbon

[0065] In an attempt to stabilise the solution, an aqueous solution of free chlorine (AFC ~ 380 ppm, initial pH * 9.8) was produced by electrochemical treatment of a diluted saline, and then pH-adjusted to approximately 6.7 by direct infusion with gaseous carbon dioxide. Based on the required shift in pH (from 9.8 to 6.7) and AFC content (as the pH changes, part of the added acidity is consumed by the chemical equilibrium that transforms sodium hypochlorite into hypochlorous acid), the DIC-to-AFC molar ratio is estimated at approximately 6.8:1. Several aliquots of the same solution were bottled in HDPE bottles, stored at 40°C to accelerate the deterioration of the solution, and kept unopened until measurement.

[0066] Figure 3A and 3B show averages of three AFC and pH measurements as a function of time. The results clearly show how solutions whose pH has been adjusted by adding gaseous carbon dioxide, and which therefore contain dissolved inorganic carbon (DIC, which can be in the form of carbonic acid or as a bicarbonate of an alkali or alkaline earth metal), are more stable over time, not only as regards their AFC content (more than 80 days were required to see a 50% reduction) but above all as regards the change in pH. Example 3: Hydrogel formulation

[0067] A hydrogel formulation containing the stabilised solution of free chlorine was developed . The use of dissolved inorganic carbon in accordance with the invention has only a minimal effect on the ionic strength or electroconductivity of the solution. Thus, in addition to stabilising a HOCI solution in the pH range of about 6.1 to about 6.75, carbonic acid or bicarbonate do not affect the ionic strength at the targeted pH, making it possible to use hypochlorous acid with more than 300 ppm of available free chlorine as the dispersing media in a gel formulation, especially where low ionic strength is critical for the formulation.

[0068] A low ionic strength hypochlorous acid solution (conductivitya0.9 mS / cm), AFC 350 ppm, pH 6.1 was used for a hydrogel formulation containing 2% sodium magnesium fluorosilicate (Laponite XLG XR from BYK Additives Ltd). A low ionic strength HOCI solution as a dispersing media allows for the addition of other buffering agents for pH optimisation in the final product without negative effects on physical appearance and product stability.

[0069] All references cited herein are incorporated by reference in their entireties.

Claims

The claims defining the invention are as follows:

1. A stabilised solution or formulation (a liquid or a thixotropic gel) packaged in a container for storage or sale, comprising hypohalous acid and a stabilising amount of dissolved inorganic carbon (DIC) incorporated in the form of carbonic acid or bicarbonate of an alkali or alkaline earth metal, wherein the solution or formulation has an available free halide (AFC) content of from 10 to 10,000 parts per million, a pH of from 4.0 to 6.75, a DIC-to-AFC molar ratio of 10:1 to 5:1 , and wherein the container is minimally permeable to CO2 or O2.

2. The stabilised solution or formulation of claim 1, wherein said hypohalous acid is hypochlorous acid.

3. The stabilised solution or formulation of any one of claims 1 to 2, wherein said AFC content and said pH are stable for at least 6 months or at least one year.

4. The stabilised solution or formulation of any one of claims 1 to 3, wherein said AFC content is from 100 to 1,000 parts per million, from 100 to 500 parts per million, or from 400 to 1,000 parts per million.

5. The stabilised solution or formulation of any one of claims 1 to 4, wherein said pH is from 5 to 6.75.

6. The stabilised solution or formulation of any one of claims 1 to 5, wherein the DIC is added as carbon dioxide.

7. The stabilised solution or formulation of any one of claims 1 to 6, wherein said AFC is prepared by electrolysis of a NaCI solution.

8. The stabilised solution or formulation of any one of claims 1 to 7, having a salinity from 0.01 to 2.0%, or from 0.02 to 1.0%.

9. The stabilised solution or formulation of any one of claims 1 to 8, wherein the solution or formulation has an AFC content of from 100 to 500 parts per million, a pH in the range of from 4 to 6.75, and a salinity of from 0.02 to 1.0%.

10. The stabilised solution or formulation of any one of claims 1 to 9, wherein the solution or formulation is formulated as a gel, cream, or foam.11 . The stabilised solution or formulation of claim 14, wherein the gel is a fluorosilicate hydrogel.

12. The stabilised solution or formulation of any one of claims 1 to 11 , wherein the container is a bottle, a bag, a tube, or a can.

13. A method for preparing the stabilised solution or formulation of any one of claims 1 to 12, comprising incorporating the DIC into the solution or formulation, in amounts sufficient to stabilise the solution or formulation for at least six months or at least one year.

14. A method for disinfecting or treating a mammalian tissue, the method comprising applying the solution or formulation according to any one of claims 1 to 13 to a mammalian tissue in need of disinfection or treatment.

15. The method of claim 14, wherein the mammalian tissue is infected or optionally comprises a wound or burn.

16. The method of claim 14, wherein the stabilised solution or formulation is applied to an affected area of a mammal having one or more dermatoses or a mammal having atopic dermatitis.

17. A method for disinfecting or cleansing a hard surface comprising applying the stabilised solution or formulation of any one of claims 1 to 12 to the hard surface, and optionally, wherein the hard surface comprises porcelain, glass, steel, iron, ceramic or polymeric material.

18. A method of treating a food product comprising applying the stabilised solution or formulation of any one of claims 1 to 12 to the food product, and optionally, wherein the solution is applied as a mist, fog, spray, or ice.

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