Controlled oxygen/anti-microbial release films

Description of equivalent WO 9426317 A1

CONTROLLED OXYGEN/ANTI-MICROBIAL RELEASE FILMS

0002Background of the Invention

0003The present invention relates to the microbial decontamination arts. It finds particular application with bandages and wipes and will be described with particular reference thereto. It is to be appreciated, however, that the present invention will also find application in other areas where oxidants, anti-microbial agents, or medicaments are generated in situ such as in gloves, drapes, and the like. Heretofore, various wipes and other cloth-like materials have been impregnated with an anti-microbial agent. The anti-microbial agent, most often in a liquid form, is coated on, caused to soak into, or otherwise attached to a flexible carrier or film. Often, the anti- microbial agent treated film is packaged in a sealed pouch to prevent evaporation or contamination. The pouch is opened to use the wipe. The wipe is typically packaged with a sufficient amount of a liquid carrier that a wet layer of carrier and anti-microbial agent are left on the wiped surface. Alternately, the carrier or a dilutant such as water may be added to the film when the package is opened to render the anti-microbial agent more mobile.

0004Flexible fabric or fiber-like materials which are apt to support mildew, mold, or bacterial growth are often treated with an anti-microbial agent. Often, the fabric or fiber carries materials, e.g., sizing which are apt to support such microbial growth. The anti-microbial agent is typically intermixed with the material which is apt to support microbial growth.

0005One of the problems with wipes and films of this type is that the anti-microbial agent requires a long shelf life. The wipe may be in the package for weeks or months before it is opened. After the wipe is used and discarded, a significant amount of the anti-microbial agent remains in the wipe. If the anti-microbial agent is a toxin or poison with a long life, disposal of the used wipe carries undesirable environmental and ecological side effects.

0006The present invention contemplates a new and improved material which overcomes the above-referenced problems and others.

0007Summary of the Invention In accordance with one aspect of the present invention, a film carries one or more constituents which in the presence of a dilutant form oxygen or a strong oxidant.

0008In accordance with a more limited aspect of the present invention, the film is one of a woven, non-woven, or knitted fibers, a flexible foam material, or combinations thereof.

0009In accordance with another aspect of the present invention, the film carries at least two reagents that react in the dilutant to form the oxygen or anti-microbial agent. A means is provided to maintain the constituents or reagents separated until contacted with a dilutant.

0010In accordance with one more limited aspect of the present invention, the means for keeping the two constituents separated includes one of a filter, micro- encapsulation, and immobile implantation of the reagents into displaced first and second layers.

0011In accordance with another aspect of the present invention, means are provided for controlling a reaction rate between the constituents to control the rate at which the oxygen or anti-microbial agent is produced. In accordance with a more limited aspect of the present invention, the means for controlling the reaction rate includes added buffers which increase the pH to accelerate the reaction rate or decrease the pH to retard the reaction rate.

0012In accordance with another aspect of the present invention, the first reagent includes an acetyl donor and the second reagent includes a perborate. Suitable acetyl donors include acetylsalicylic acid which react with a perborate, preferably sodium perborate monohydrate or sodium perborate anhydrous to form peracetic acid and salicylic acid. The peracetic acid is a strong oxidant which decomposes to liberate free oxygen. The salicylic acid is a keratotic. Other suitable acetyl donors include tetraacetyl ethylenediane (TAED) , diactyl dioxohexahydratriazine (DADHT), tetraacetyl glycoluril, and sodium nanonoyl oxygenzene sulfonate.

0013In one method of use, the film material is formulated such that the constituents react quickly, i.e. have a very short half-life. The film or the surface to be disinfected are wet, such as by spraying or dipping. The dilutant allows the constituents to react, generating the anti-microbial agent or oxidant. Preferably, the half-life of the anti-microbial agent or oxidant is only a minute or two.

0014In accordance with another aspect of the present invention, the film is incorporated in a bandage and configured such that the reaction progresses very slowly, i.e. there is a long half-life. The bandage is placed over a wound. Moisture from the wound acts as the dilutant allowing the reaction which produces the anti-microbial agent and/or oxidant to take place. Preferably, the half- life is on the order of several hours to a day or two such that the anti-microbial agent or oxygen is produced substantially continuously over the time that the dressing is applied to the wound. One advantage of the present invention is that it has a relatively long shelf-life and a relatively short half-life.

0015Another advantage of the present invention is that the anti-microbial agent or oxidant. is generated in situ at a controllable rate.

0016Another advantage of the present invention is that it effectively kills microbes yet is not polluting when discarded. Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.

0017Brief Description of the Drawings The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating a preferred embodiment and are not to be construed as limiting the invention. FIGURE 1 illustrates a film impregnated with dry reagents which react in the presence of a dilutant to form an anti-microbial agent or oxidant;

0018FIGURE 2 illustrates another embodiment of the present invention in which reagent particles are separated by a filter;

0019FIGURE 3 illustrates another embodiment of the present invention incorporated into a wipe;

0020FIGURE 4 illustrates a wound dressing in accordance with the present invention; FIGURE 5 illustrates another embodiment of the present invention which may advantageously be incorporated into the dressing of FIGURE 4;

0021FIGURE 6 illustrates yet another embodiment of the present invention in which the reagents are micro- encapsulated; FIGURE 7 illustrates a glove incorporating the present invention; and,

0022FIGURES 8 and 8A illustrate a brush incorporating the present invention.

0023Detailed Description of the Preferred Embodiments

0024With reference to FIGURE 1, a film 10 is impregnated with a first reagent or constituent 12 and a second reagent or constituent 14, which reagents react in situ in the presence of a dilutant to form an anti- microbial agent, a strong oxidant, or oxygen. In one preferred embodiment, one of the reagents 12 includes a sodium or other perborate in dry form or other dry constituents which liberate oxygen. Sodium perborate monohydrate and sodium perborate anhydrous are preferred. The other reagent 14 includes a dry acid precursor. The dry acid precursor and the dry persalt react when dissolved in water or other appropriate dilutants to form a strong oxidant. Further to the preferred embodiment, the acid precursor is an acetyl donor, such as acetylsalicylic acid, tetraacetyl ethylenediane (TAED) , diactyl dioxohexahydratriazine (DADHT), tetraacetyl glycoluril, and sodium nanonoyl oxygenzene sulfonate. Acetylsalicylic acid and sodium perborate react in water to form peracetic acid, salicylic acid, and sodium metaborate. Peracetic acid is a strong oxidant with a relatively short half-life that liberates free oxygen as it breaks down. Salicylic acid is a topical keratotic which softens or dissolves horny layers of the epidermis such as warts, callouses, and dead skin. In addition to softening skin, salicylic acid has anti- microbial properties.

0025Single constituent systems which react in a solvent, such as water, to release oxygen are also contemplated. Preferred single constituents include stable solid acetyl peroxyborate, magnesium monoperoxy phthalate, and urea peroxide. In use, the film 10, an open cell foam in the embodiment of FIGURE 1, is brought into contact with water or other dilutant such that the physically displaced implanted dry acid precursor and dry persalt or the single constituent are dissolved and react forming an anti¬ microbial agent and liberating oxygen. When used as a wipe, the film may be dipped or sprayed with water to activate it. Alternately, the surface to be disinfected may be wet such that the film and the impregnated reagents become wet, dissolve, and react from the water on the surface. When used as a bandage, the film may be initially dampened, such as with spray, to start the reaction. The reaction may be continued or in some embodiments initiated by moisture from the wound. When used as a dressing, the oxidant disinfectant agent not only functions as an anti¬ microbial agent to prevent infection, but also liberates free oxygen which promotes healing.

0026With reference to FIGURE 2, rather than implant the dry constituents or reagents 12, 14 physically displaced from each other, other means can be provided for maintaining the dry constituents separated until activated by the dilutant. In the embodiment of FIGURE 2, particles of the first reagent 12 and particles of the second reagent 14 are separated by a filter sheet 18. The filter sheet has a pore size which is sufficiently small relative to the particle size of the two powdered reagents that the particles are maintained physically separated. Yet, once dissolved in the dilutant, the pore size is sufficiently large that the dilutant and dissolved materials pass therethrough and react. A top or first outside coating layer 20 and a bottom or second outside coating layer 22 shield the particles of the two reagents from physical interaction so that they are not lost or brushed off before the film is actuated with the dilutant. At least one of the two covering layers is permeable to the dilutant to allow ready access to the constituents. It is also advantageous to control the reaction rate such that the rate at which the anti-microbial agent or oxygen is produced occurs substantially at a preselected rate. In the embodiment of FIGURE 2, a means for controlling the reaction includes the pore size of the filter material 18. In one embodiment, the reaction rate is controlled by limiting communication between the constituents. The means for controlling the reaction rate further includes the permeability of the covering layers 20 and 22. By limiting the rate at which the dilutant can reach the dry constituents, the rate at which there is sufficient dilutant to allow them to react is controllable. In another embodiment, the means for controlling the reaction rate includes the addition of further powdered reagents. In particular, the reaction between the preferred acetylsalicylic acid and sodium perborate is pH sensitive. At a high pH, the reaction occurs quickly. When the pH is buffered such that it remains near neutral even when the peracetic acid is produced, the reaction proceeds more slowly. The peracetic acid buffered nearer neutral remains stable for a relatively long duration, generally on the order of hours, rather than breaking down into oxygen quickly as it does when the pH is high. Lower pH serves as a stabilizer. Analogously, temperature affects the reaction. The maximum yields of peracetic acid are higher at 20° C while the times needed to reach the maximum are longer at lower temperature. The time for converting TAED to peracetic acid is longer than for DADHT.

0027With reference to FIGURE 3, the film 10 includes readily porous upper and lower layers 20, 22 between which the powdered reagents are contained. A dry, moisture absorbing gel material 24, such as sodium silicate, separates the dry first reagent 12 and second reagent 14. The dry gel 24 absorbs moisture strongly .forming a wet slush which permits the powdered constituents 12 and 14 to mix and react. A hermetic seal, such as a plastic or cellophane package or a foiled pouch 26 encompasses and seals the film 10 to prevent moisture from being absorbed by the gel and starting the reaction prematurely. The gel may be formulated chemically or configured physically, such as by the addition of a porous fabric layer, to control the rate at which the dry reagents are dissolved and intermix to react. Further, the dry reagents may again be encapsulated to control the reaction rate. pH buffers or other reaction controlling constituents are preferably physically intermixed with either the first, or the second powdered reagent or the gel. The dry reagents of the wipe may also include surfactants or wetting agents, detergents, moisture absorbing gels to remove water from the wiped surface, and the like.

0028With reference to FIGURE 4, a wound dressing 30 includes a section of the film 10 disposed between a gauze or other porous wound contacting layer 32 and a covering layer 34. Preferably, the covering layer 34 includes an adhesive layer 36 which adheres to the film 10 to a central portion thereof, adheres the wound contacting portion 32, and adheres to the patient's skin around the wound. The film 10 may have the construction set forth in any of the preceding FIGURES or in those described below. In one preferred embodiment, the film 10 has substantially the construction of FIGURE 2. The lower layer 22 disposed towards the patient's skin is porous to moisture exiting the wound. Lower layers of different porosity are used for different types of wounds. For example, the bandage is advantageously used to generate oxygen to promote the healing of a wound. The lower layer 22 has a porosity which permits water vapor to pass therethrough at a controlled rate. The water vapor causes a limited wetting of the dry reagents such that they dissolve gradually and react, at an analogous controlled rate. Preferably, the powdered constituents are buffered to have a relatively high pH such that the preferred acetylsalicylic acid and perborate form a peracetic acid with such a high pH that it is relatively unstable and breaks down quickly to free oxygen. A pH of 11 or higher is preferred for a quick breakdown to oxygen. The porosity of the lower layer 22 is again permeable to the free oxygen such that it enters the wound. The upper layer 20, being redundant with the layer 34 may be eliminated. The layer 34, and layer 20 if redundantly applied, may be moisture and gas permeable or may be semipermeable to either moisture or gas. Venting allows excess water vapor to escape. In some applications, layer 34 is impermeable. For other types of wounds, the generation of a strong anti-microbial agent is important as well as the production of oxygen. The porosity of lower layer 22 is again selected to control the amount of moisture permitted to enter. If the dressing is to be applied for a relatively short duration, e.g. a few hours, the lower layer 22 is preferably permeable by liquids such as water vapor from the skin, liquids exiting the wounds, or water sprayed from a spray bottle to actuate the dressing.

0029The preferred acetylsalicylic acid and perborate react to form not only peracetic acid, but also salicylic acid. Preferably, the lower layer 22 is sufficiently porous that it allows the dilutant with dissolved salicylic acid to flow back into the wound to promote healing. As another alternative, the salicylic acid can be used to remove horny layers of the epidermis. The film may be wet, such as by spraying or dipping and then applied to the area to be treated. Preferably, the dry constituents include a gel which holds the water and continues the reaction and permits the salicylic acid solution to continue to reach the horny layer for several hours to a day. For relatively longer stability, an after reaction pH of 9.2-10 is preferred. The dry reagents 12 and 14 may also include emollients and other skin softeners.

0030With reference to FIGURE 5, the constituents 12 and "4 are carried by layers of woven, non-woven, or knitted fibers or open cell or foam 40, 42. The dry constituents are sprayed and dried, impregnated, dry sprayed, or otherwise attached to or incorporated into the fibers or foam layers. A filter layer 18 holds the dry particulates apart. Outer layers 20 and 22 contain and protect layers 40 and 42. At least one of the outer layers is fluid permeable such that the dilutant can penetrate, dissolve the dry constituents, and start the chemical reaction. The porosity of the filter 18 and the outer layers 20, 22 control the rate at which the dilutant can enter and the reagents intermix, hence the rate of reaction. Additional buffering compositions may also control the rate of reaction. Surfactants, detergents, emollients, and the like may also be included in dry form.

0031In the embodiment of FIGURE 6, the single constituent or one or both of the dry reagents 12 and 14 are micro-encapsulated individually. The thickness and the type of the micro-encapsulation controls the reaction rate. For a longer reaction rate, some of the micro- encapsulations are thin to react quickly, others thicker to react more slowly, and others thicker yet such that an extended duration is required before the dilutant penetrates the encapsulation and reaches the dry constituent. The micro-encapsulated constituents or reagents are between outer layers 20, 22. At least one of the outer layers is porous to permit the dilutant to enter and the resultant anti-microbial agent, oxidant, or free oxygen to exit.

0032With reference to FIGURE 7, the constructions of the preceding embodiments can be fabricated into various articles. For example, a protective glove 50 is defined by a continuous impermeable hand-shaped layer 52 of rubber, plastic, or other film material which is impermeable to the dilutant, the anti-microbial agent, strong oxidants, and gaseous oxygen, as well as any emollients, detergents, or other substances which may be dissolved in the dilutant. The film 10 is adhered to the outer surface of all or selected portions of the glove. The film 10 is preferably laminated over the palm, thumb, and finger pad portions of - li ¬ the glove, i.e. the portions of the glove which would contact a grasped or touched object. An outer, permeable layer 22 surrounds the film 10 protecting it. Preferably, the outer layer 22 is a material which can be readily affixed to the impermeable liner 52, such as by heat fusion, adhesives, or the like. Preferably, the film 10 has periodic discontinuities where the inner and outer layers contact and adhere to each other.

0033With reference to FIGURES 8 and 8A, the single or the plural constituents 12, 14 are impregnated in bristles 60 of a brush 62. The bristles may be natural or synthetic fibers or other constructions which securely hold the dry constituents. When the brush is dipped into a dilutant, the constituents react forming an anti-microbial for scrubbing a surface.

0034Although the preferred embodiment uses an acetylsalicylic acid and sodium perborate reaction, other oxidizing or antimicrobial agents can also be generated in situ , such as chlorine dioxide, chlorine, hydrogen peroxide, and mixtures thereof. More specifically, potassium chromates, sodium chloride, and phosphates may be mixed according to the following equation to produce a strong chlorine oxidant on the addition of water:

0035K₂Cr₂0₇ + 6 NAC1 + 7 H₃P0₄ → 4 K₂HP0₄ + Cr₂N(HP0₄)₃ + HOCl + 6H⁺ + H₂0

0036Optionally, excess dichromate and an organic corrosion inhibitor may be provided for improved buffering and corrosion inhibiting.

0037Hydrogen peroxide and an inorganic inhibitor can be generated:

0038NaB0₃ + H₂0 + H₃P0₄ → H₂0₂ + NaB0₂ + H₃P0₄

0039Similarly, chlorine dioxide can be generated from powdered ingredients on the addition of water:

00402NaCl0₂ + LiClO + H₂0 → 2C10₂ + NaOH + NaCl + LiOH A mixed biocide system can be achieved by adding sodium chloride to the peracetic acid reaction to produce hypochlorous acid. Because sodium chloride is a component of physiological fluids, the reaction can be partially physiologically regulated.

0041CH₃COOOH + Na⁺ + Cl-→ CH₃COONa + H0C1 Excess peracetic acid is deliberately present such that both peracetic acid and hypochlorous acid are present in the biocidal solution.

0042Other reagents include perborates which react in water to liberate free oxygen, and constituents which react to form other medically useful compositions. The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.