CA2339823A1

CA2339823A1 - Inherently antimicrobial quaternary amine hydrogel wound dressings

Info

Publication number: CA2339823A1
Application number: CA002339823A
Authority: CA
Inventors: James J. Perrault; Cameron G. Rouns
Original assignee: Individual
Current assignee: Kimberly Clark Worldwide Inc
Priority date: 1998-09-01
Filing date: 1999-08-30
Publication date: 2000-03-09
Also published as: WO2000012100A1; US6039940A; AU5785099A; DE69918707T2; EP1123104A4; MXPA01002247A; JP2002523565A; EP1123104B1; EP1123104A1; DE69918707D1

Abstract

A composition and method for treating a wound with an inherently antimicrobial dressing. The dressing is a hydrogel containing from about 15 to 95 percent, and preferably from about 61 to 90 percent, by weight of a cationic quaternary amine acrylate polymer prepared by the polymerization of acryloyloxyethyl(or propyl)-trialkyl(or aryl)-substituted ammonium salts or acrylamidoethyl(or propyl)-trialkyl(or aryl)-substituted ammonium salts. The antimicrobial hydrogels are non-irritating to the wound, absorb wound exudate, and, due to the inherently antimicrobial properties, enhance the sterile environment around the wound. The hydrogels have sufficient adhesive properties that loose contact with the wound is assured but can also be removed without leaving any gel residue on the wound. The wound dressings are preferably formed on a substrate, such as a web or patch, for ease in application to and removal from the wound. If desired, additional antimicrobial or other pharmaceutically active agents can also be incorporated into the hydrogel structure.

Description

WO 00112100 PCT/US99/19441_ HYDROGEL WOUND DRESSINGS
This application is a continuation-in-part of pending application Serial No.. 08/738,651 filed October 28, 1996 and issued September 1, 1998 as il.S.
Patent 5,800,685.
This invention is drawn t:o hydrogel wound dressings that are inherently antimicrobial. More particularly, this invention is drawn to inherently antimicrobial hydrogels containing wound dressings wherein the hydrogel is formed by the polymerization of acrylated quaternary ammonium monomers in an aqueous media.
In the past, wounds have been treated with antimicrobial active agents a~>plied to the wound and covered with a covering that inhibits the healing process. For example, it was conventional practice early in the 20th Century to apply an antiseptic mercury agent such at thimero~~al (Merthiolate) or merbromin (Mercurochrome) and the like to a wound and then cover or wrap the wound with a bandage such as gauze or an adhesive strip having a central absorbent gauze portion.
A disadvantage of this approach is that the wound often weeps or exudes fluids ~~uch as blood, pustulation and the like. While the gauze may absorb some of these fluids, the gauze often adheres to the wound such that removal of the: dressing reopens the wound.
Advances in the art have been made in both bandages and antimicrobial agents. Certain bandages now contain a nonadhering polymeric coating over or, in place of, the gauze that inhibits the adhering of the absorbent material to the wound but also inhibits the absorption of the exudate that is necessary to properly heal the wound.
Certain wound dressing materials have been used to absorb exudate and promote healing. For example, 5 Mason, et al., U.S. Patent No. 4,393,048 teaches a hydrogel composition which, wlhen applied as a powder, absorbs wound exudate. The hydrogel formation may not be complete and lumps of partially hydrated powders form which, when removed, may reopen the wound.
10 It is known that wounds heal more rapidly and completely if kept in a slighitly moist or hydrated state. Polyethylene glycol containing hydrogel wound coverings are disclosed in Spence, U.S. Patent 4,226,232. These hydrogels cannot be sterilized by 15 irradiation due to the formation of free radicals.
Rawlings et al., U.S. Paitent 4,657,006, illustrate wound dressings comprised of a hydrophilic polymer having moisture and vapor permeability properties. However, the exud<~te absorbed by the 20 hydrophilic polymer tends to harden or solidify the polymer.
An ideal wound dressing ;should not only absorb exudate but also possess antirnicrobial properties. For example, Matson, U.S. Patent 4,728,323 discloses a 25 wound dressing comprising a substrate coated with an antimicrobial coating of a silver salt that allegedly keeps the wound moist.
Korol, U.S. Patent 4,563,,184, discloses wound dressings comprising a polymer, such as poly(2-30 hydroxyethylmethacrylate), a :>olvent, such as polyethylene glycol, and a plasticizer such as DMSO.
An antimicrobial agent, such as silver sulfadiazine, may be incorporated into the polymeric material.
Widra, U.S. Patent 4,570,629, is drawn to 35 absorbent hydrogel membrane wound dressings made up of hydrophilic biopolymeric copolyelectrolytes comprising a water-soluble linear anionic protein polyelectrolyte component derived from keratin and a water-soluble linear cationic biopolymer po.lyelectrolyte component 5 derived from either collagen or a glucosamineglycan.
The membranes may also contain antibiotics.
Klemm et al., U.S. Patent 4,191,743, teache the administration of antibiotics to wounds using a wound dressing comprising at leastwtwo layers of synthetic 10 resin arranged one above the other having an intermediate layer composed oa a synthetic resin granulate having an antibiotic incorporated therein.
It is known that certain quaternary amine salts possess antimicrobial properties. Examples include 15 benzethonium chloride and ben;zalkonium chloride (Bactine~). Tt is also known i~hat certain quaternary amines can be incorporated ini:o polymeric substrates to provide a certain degree of antimicrobial activity.
Rebaum et al., U.S. Patent 3,898,188, teach 20 cationic polyelectrolytes homopolymers formed from an alkyl amine halide monomer that are useful for various medical applications. These polymers are formed by the head-to-tail qu<~ternization reaction of the monomer to form linear chains. Such 25 polyelectrolyte homopolymers are taught to possess bacteriocidal activity and can be topically applied to traumatic skin areas such as in the treatment of burns, abrasions or cuts. However, the homopolymers do not possess gel forming capabilities and, in order to 30 form a moisture retaining structure, must be combined with a polyvinyl alcohol or polyvinyl pyrrolidone polymer. Such combinations re:>ult in films that can impregnate gauze materials to form an antiseptic or germicidal dressing material. The homopolymers may 35 also be converted to branch polymers having a comb-WO 00/12100 PCT/US99/1944I_ like structure by attaching the quaternary homopolymer to the backbone of a polymeric substrate such as a poly-dialkylaminoalkylacrylates or a polyalkylaminoacrylamides. Such comb-like polymers are 5 useful for coating onto substrates such as photocopy paper. Further, the polyelectrolyte monomers can be copolymerized with anionic polymers such as polystyrene sulfonates, polyacrylates or heparin to provide copolymers that can coat surfaces such as 10 tubes, catheters, valves and the like with a non-thrombogenic coating.
Hou et al., U.S. Patent 4,791,063, teach polyionene-transformed modified polymer-polysaccharide separation matrices for use i:n removing contaminants 15 of microorganism origin from lbiological liquids. This patent teaches that absorption of bacterial cells by ion-exchange resins is attributable to electrostatic attraction between quaternary ammonium groups on the resin surface and carboxyl groups on the bacteria cell 20 surface.
Hansen et al., U.S. Pate:nt 5,498,478 is directed to the use of a polyethylene glycol or similar polymer as a binder material for fibers of any variety. The binder and fibers may be pretreated by slurrying the 25 fibers in baths containing antimicrobial agents as part of the solution, thereby causing the fibers and the subsequently formed matri:K of polymer and fibers to have an antimicrobial ability.
Mixon et al., U.S. Patent 5,069,907 is directed 30 to the formation and use of a polymeric sheet which may include an antimicrobial agent. This patent teaches of the inclusion of antimicrobial agents into either a pressure-sensitive 1<~yer, such as an adhesive, or in a drape used to cover a wound or other 35 sensitive area.

Dietz et al., U.S. Pateni~s 5,674,561 and 5,670,557 are directed to pol~,~merized microemulsion pressure sensitive adhesive compositions that may optionally contain antimicrob_i.al and/or other 5 biologically active agents. The potential antimicrobial activity of quat:ernary amine and quaternary ammonium salts is taught. It is further taught that an antimicrobial agent can be added so as to be contained in a specific layer of a pressure sensitive adhesive device for use as a medical skin covering and/or as a wound dressing.
Young et al., U.S. Patent: 5,432,000, teach the use of a polymeric network foi: adhering particulate materials to a fiber or fibrous product.
Specifically, this patent teaches of the use of polymers, such as polyethylene' glycol or polyethylene to cause the binding of particulate materials to a fiber, such as cloth. One such particulate member which could be adhered to cloth is an antimicrobial agent, such as epoxide phenol or another antimicrobial substance.
There is a need for a wound dressing that incorporates the desired properties of exudate absorption, moisture retention to the wound and antimicrobial properties into a single hydrogel structure. Such has not been ~>reviously demonstrated in the prior art.
OBJECTS AND SUI~lARY OF THE INVENTION
It is therefore an object. of the present invention to provide a cationic quaternary amine polyacrylate hydrogel wound dressing that is inherently antimicrobial.
Another object of this invention is to provide a hydrogel wound dressing that absorbs wound exudate and WO 00112100 PCT/US99/19441_ allows the wound to remain in a hydrated or moist occlusive condition.
A still further object of the invention is to provide a hydrogel formed from the polymerization of cationic quaternary amine acrylic acid ester or amide monomers wherein the formed polymers are inherently antimicrobial and, when hydrated, provide hydrogel dressings having an adhesive quality that loosely adheres to the wound to keep the wound hydrated, absorb exudate and yet is readily removed without aggravating the wound healing process.
Another object of the invention is to provide a method for treating wounds by applying to the wound an inherently antimicrobial cationic quaternary amine containing polyacrylate hydroge:L to promote healing, absorb exudate and retain the wound in a moist or hydrated condition.
These and other objects are accomplished by means of an aqueous hydrogel composition comprising between about 15 to 95~ by weight of a cationic quaternary ammonium polyacrylate polymer o:~ following Formula I:
' ~z~~,_R..
n R "' 3 0 ~ F4RML1LA. ~:
wherein n is an integer of 2 to 3; R', R" arid R" ' are independently selected from the group consisting of H, C1 to C16 alkyl, aryl, aryl.amine, alkylamine, alkaryl and aralkyl: X is selected from the group consisting of O and NH; Y' is an acceptable anionic counterion to the N+ of the quaternary amine and m is an integer greater than 50,000.
Alkyl groups are preferably lower alkyl, of Cl to C$ with methyl or ethyl groups being particularly preferred. Aryl is preferably phenyl but can be any suitable aromatic moiety such as those selected from the group consisting of phenyl, thiophenyl, naphthyl, biphenyl, pyridyl, pyrimidinyl, pyrazyl, pyridazinyl, furyl, thienyl, pyrryl, quinolinyl and bipyridyl and the like. Representative of a:n aralkyl grouping is benzyl and representative of .an alkaryl grouping is tolyl. X is preferably O or N:H. Representative of counterions represented by Y' are members selected from the group consisting of C1', E3r', HS04', and GH3S04' with C1' being particularly preferred. Alkyl groups can be straight or branched chained .and alkyl and aryl groups can be substituted by non-interfering substituents that do not obstruct with the functionality of the polymers.
The cationic quaternary ammonium polymer can be prepared in an aqueous medium and form an hydrogel in situ or can be prepared in an aqueous medium, dried and converted into a powder which can then be reconstituted in aqueous media as a hydrogel.

The polymer is prepared by the polymerization of an acrylic acid monomer according to following Formula II:
X
to H2C
n "'R N-R' ~+
R..
m FORM~TLA I7C
where n, R' , R" and R"' , X, Y' have the meanings given above in Formula I. Polymerization is brought about by methods known in the art such as free radical curing with an initiator induced polymerization in the presence of water by ultra-violea curing and a multi-functional cross-linking agent or by anionic 1,2 alkoxy anion induced polymerization.
The cationic quaternary ammonium polymers of this invention possess inherent microbiocidal properties and are absorbent and non-irritating to the skin or open wounds. The absorbency of the hydrogel means that, when applied as a wound dressing, fewer dressing changes are necessary, the wound heals faster and a moist healing environment is maintained. The polymers are radiation tolerant and can be sterilized by such means. Because the polymers are inherently microbiocidal, the wound is retained in a sterile environment to promote healing. Further, because the polymers are polycationic, it is possible that healing is accelerated because blood clotting is promoted due to the cationic polymer neutralizing polyanionic clotting inhibitors such as tlhe naturally occurring anionic polysaccharide heparin.
The hydrogeis are preferably prepared with a physical support structure to better retain the hydrogel over a wound. This physical support structure may be in the form an occlusive device having an impermeable backing, i.e. a p<~tch. Since hydrogel is both inherently adhesive as w<sll as antimicrobial, the use of more permanent adhesivE~s may or may not be beneficial. The hydrogel can also be formed around a web or fibril support and fashioned by cutting into suitable sizes in both surfaces area and depth, i.e.
sheets, strips, squares, circles, ovals, etc.
DETAILED DESCRIPTION OF THE INVENTION
The cationic quaternary amine polyacrylate gels of the invention are able to absorb significant amounts of fluid or exudate ennanating from a wound or other skin surface abrasion. 7Ct is known that the accumulation of excess wound E:xudates is detrimental to healing and provides a fertile site for the growth of bacteria which further inhibits the healing process. Due to the absorbency of the hydrogels, the change of wound dressings can occur less frequently and still retain a sterile eni~ironment. Or, in the alternative, the wound dressing can be changed as needed if exudate production i.s high.
The cationic hydrogels maintain the wound in a moist condition which not only facilitates healing but also enhances the cosmetic appearance of the wound as it heals.
As previously noted, in order to maintain or promote sterility and enhance healing, an external 5 antibiotic or other disinfectant has been added to prior art hydrogels and/or wound dressings. While such external antibiotics may still be added if it is deemed necessary, the inherent antimicrobial properties of the present hyd.rogels may make the 10 additions of such external additives unnecessary. As will be seen; the antimicrobi,al properties of the hydrogels of this invention a:re effective agents against a wide range of microlbes:
Another distinct advantage of the cationic quaternary amine polyacrylate hydrogels is sterilization. Suppliers of dressings generally place them in a sealed environment :in a sterile condition.
Because hydrogels are absorptive to steam and other sterilization agents, such as ethylene oxide, they 20 cannot be sterilized by such means and the use of radiation is inimical to the ;stability of many prior art gels due to free radical degradation. The hydrogels of the present invention can be irradiated and sealed without adverse af:~ects to the stability, 25 adhesivity or antimicrobial properties of the hydrogel. Due to the ability of the polycationic hydrogels to be sterilized by radiation, they do not have to be formed or packaged in a "clean room" or sterile environment.
30 As noted in co-pending application Serial No.
08/73$,651 referenced above (issued September 1, 199$
as U.S. Patent 5,800,685), cationic quaternary amine polyacrylate hydrogels are good electrical conductors and can be formulated for use as electrodes in medical 35 devices because they contact t:he skin with sufficient wetness and adhesive properties to allow passage of electrical current without substantially adversely affecting either the hydrogel. or the skin.
When used as conductive adhesive hydrogels, high amounts of an electrical conductivity enhancer, such as potassium chloride, are generally added to the formulation. In the present invention; salt solutions of sodium or potassium chloride, at lower concentrations, may be present as polymerization 10 enhancers in the formation of the hydrogels.
When using the cationic hydrogeis as wound dressings, the gel may also contain a buffer system to help prevent discoloration and/or hydrolysis of the hydrogels, and/or improve their shelf-life. Other 15 additives may also be added to the hydrogels either before or after curing (i.e. pharmaceuticals, humectants, plasticizers, etc.). The appropriateness of such additives is generally dependent upon which dressings are to be formulated and applied to a wound.
20 In addition to the absorbency of exudate and the inherent antimicrobial properties, there are other properties that make the present cationic acrylate hydrogels beneficial as wound dressings. They possess excellent physical characteristics in adhesiveness in 25 that they both adhere to the skin when applied but are readily removable from the skin without leaving any gel residue. Also, when compared to prior hydrogels, the present cationic acrylate hydrogels are effective over a wide range of hydration. In other words, the 30 gel may contain as little as :15 or as much as 95% by weight of the cationic polyac:rylate. Preferably, the hydrogel will contain between about 61 to 90% by weight of the polyacrylate po:Lymer with ranges of between about 65 to 75% by weight being particularly 35 preferred. Even at the higher solids content of the polyacrylate polymer, the hydrogels are relatively non-irritating to the wound or skin surface.
The preferred chemical formula for cationic quaternary amine polyacrylates suitable fox the present invention is shown in Formula I above. The quaternary amine containing acrylic acid ester or amide monomers that may be used for the polymerization process are shown in Formula II. The preferred method for making such cationic acrylates suitable for the present invention is described below.
Generally, the polymerization process will proceed in an aqueous solution such that the hydrogel formed will contain the solids content mentioned above with the balance being water or other additives as i5 also mentioned above. If desired, the hydrogel may also include sufficient buffer to maintain the pH of the hydrogel in any desired pH range.
Examples of specific quaternary amine cationic acrylate ester or amide monomers that may be polymerized are shown in following Formulas III, IV, V
and IV.
H
HzC=C
C=O CH3 2 5 O-C-C-N+-CH,i HZ HZ CH C

FORMULA III
Formula III shows acryloyloxyethyltrimethyl ammonium chloride which is available from CPS Chemical Co.

H
HiC~ 1 I-_O ~H~
O-C-C-N'-CHI (CH~SO~j' H2 Hx CHI
1o FoRMVLA iv Formula IV shows acryloyloxyethyltrimethyl ammonium methyl sulfate which is available from Allied Colloid Co.
H
H=C=C
C=O Cfl3 ~
H-N- (CH2)~ -N"--CHI
t cr CHIs FORMULA V
Formula V shows acrylamidopropyltrimethyl ammonium chloride which is available from Stockhausen (Germany).

p H2 t~-i3 _ CwC I Y
CH H'''NI+ CH3 t~Z
I5 FORMDLA V'I
Formula VI shows acryloxyethyldimethylbenzyl ammonium chloride which is available from Elf Atochem.
The preferred process for :making cationic quaternary amine polyacrylate hydrogels from one or more of these specific monomers is described in detail below.
The cationic quaternary amine polyacrylate hydrogels are preferably formed by in situ free radical polymerization of a water soluble monomer (such as those shown above) in the presence of water, preferably by ultra-violet curing with initiators) and multi-functional cross-linking agent(s). For example, an appropriate acrylat~e monomer (as shown in Formula III), water, optional additional ' polymerization enhancer (e. g. salt, for example, sodium chloride, potassium chloride, etc.), initiator or catalyst (e. g. a-hydroxy-l,a~-dimethylacetophenone in DMSO, etc.), and a multi-functional cross-linker (e. g. methylene-bis-acrylamide, etc.) are combined, placed in a mold, and exposed to ultraviolet radiation as is known in the art. The resultant cationic quaternary amine polyacrylate hydrogel formed is somewhat clear in color, viscous, and tacky to the touch. The hydrogel tends to be sufficiently adhesive 5 to a subject's skin for purposes of wound dressing, yet sufficiently cohesive to :be easily removable from the subject's skin and separalble from itself.
As mentioned above, the ;present hydrogels may include a buffer system to help control the pH, help 10 prevent discoloration, and/or help prevent breakdown due to the extended presence of water (i.e. help prevent hydrolysis). Buffers, if any, are preferably added to the mixture prior to curing. Suitable buffers include, for example, but are not limited to, 15 sodium potassium tartarate, and/or sodium phosphate monobasic, both of which are commercially readily available from, for example, i!~ldrich Chemical Co. , IN.
The use of a buffer system with the present hydrogel is preferred to provide the hydrogel with a 20 commercially suitable shelf-life (i.e. a shelf-life of over one year) without discoloration.
As is also mentioned above, other additives may be included in the present hydrogels either before or after curing (i.e. pharmaceuticals such as 25 antibiotics, disinfectants and the like, humectants, plasticizers, etc.). The appropriateness of such additives is generally dependE:nt upon the intended end use of the particular hydroge:L as a wound dressing.
As is mentioned above, initiators are preferably 30 used in the polymerization of the present hydrogels.
Examples of initiators which may be used include, for example, IRGACURE~ 184 (1-hydroxycyclohexyl phenyl ketone), and DAROCURE~ 1173 (a-hydroxy-1, a-dimethylacetophenone) which ax°e both commercially 35 available from Ciba-Geigy Cord>. These UV catalysts are preferred because they axe non-yellowing. Other initiators which maintain the preferred water-white and water-clear appearance of the hydrogels are preferred. However, additional examples of initiators.
5 (which may be photo initiators or thermal initiators) may include benzoyl peroxide, azo-bis-isobutyro-nitrile, di-t-butyl peroxide, bromyl peroxide, cumyl peroxide, lauroyl peroxide, isopropyl percarbonate, methylethyl ketone peroxide, cyclohexane peroxide, t-10 butylhydroperoxide, di-t-amyl peroxide, dicumyl peroxide, t-butyl perbenzoate, benzciin alkyl ethers (such as benzoin, benzoin isopropyl ether, and benzoin isobutyl ether), benzophenones (such as benzophenone and methyl-o-benzoyl benzoate), acetophenones (such as 15 acetophenone, trichloroacetap:henone, 2,2-diethoxyacetophenone, p-t-but;yltrichloro-acetophenone, 2,2-dimethoxy-2-phenyl-acetop:henone, and p-dimethylaminoacetophenone), tlhioxanthones (such as xanthone, thioxanthone, 2-chlorothioxanthone, and 2-20 isopropyl thioxanthone), benz;yl 2-ethyl anthraquinone, methylbenzoyl formate, 2-hydroxy-2-methyl-1-phenyl propane-1-one, 2-hydroxy-4'-isopropyl-2-methyl propiophenone, a-hydroxy ketone, tetramethyl thiuram monosulfide, allyl diazonium ;salt, and combination of 25 camphorquinone and ethyl 4-(N,N-dimethylamino) benzoate. Other initiators may be found in, for example, Berner, et al., "Phoito Tnitiators -- An Overview," J. Radiation Curing (April 1979), pp. 2-9.
The amount of initiator :is preferably within the 30 range of about 0.02 to 2.0~ by weight based on total amount of monomer, and more preferably within the range of about 0.05 to 0.5o by weight based on total amount of monomer.
UV curing parameters to achieve desired polymer 35 properties are well known to those skilled in the art.

An initiator for the present ,purposes tends to operate by absorbing select wavelengths of UV light, and breaking down into free radicals to initiate polymerization. The wavelengths and curing area set 5 the style of UV bulb used in the curing process.
Inhibition of polymerization due to dissolved oxygen, monomer preservatives, or other components may be overcome by changing the power, by pulsing, and/or by using catalyst accelerators. The amount of residual 10 monomer (after polymerization) is preferred to be less than about 3% for good biocom~?stability.
As is also noted above, cross--linking agents are preferably used to cross-link the present cationic polyacrylate hydrogels. Exams?les of multi-functional 15 cross-linking agents which ma~,r be used axe methylene-bis-acrylamide (MBA) and diethylene glycol diacrylate, which are both commercially a~;railable from Polysciences, Inc., Warrington, Pennsylvania.
Additional examples of cross-.Linking agents which may 20 be acceptable for use in the present invention include ethylene glycol diacrylate, triethylene glycol-bis-methacrylate, ethylene glycol--bis-methacrylate, ethylene glycol-dimethacrylate, bisacrylamide, triethyleneglycoi-bis-acrylate, 3,3'-ethylidene-bis 25 (N-vinyl-2 -pyrrolidone), trimethylolpropate trimethacrylate, glycerol trinnethacrylate, polyethylene glycol dimethacrylate, and other polyacrylate and polymethacry7-ate esters.
The amount of cross-linking agent used is 30 preferably within the range of: about 0.02 to 2.0% by weight based on total amount c>f monomer, and more preferably within the range of about 0.05 to 0.5% by weight based on total amount of monomer.

There follows specific exemplary embodiments of cationic quaternary amine acrylate hydrogels of the present invention.
In each of the following examples the acrylate quaternary amine monomer utilized was 80%
acryloyloxyethyltrimethyl ammonium chloride in water (AAC), the cross-linking solution was 1% methylene-bis-acrylamide in water (MBA), the catalyst was 0.01%
a-hydroxy-l, a-dimethylacetophenone in DMSO (DAROCURE~
11?3).
EXAMP?~3~ 1 Inaredients: Amount:
AAC 122 grams 2% Saline 80 grams 1% MBA 20 grams Darocure 1173 800 ,ul These materials were mixed in the order given and placed under a suitable UV curing system, as described above, and cured according to processes well known in the art.
The resultant gel was transparent, had a light tack and had a solids content of 61% by weight.
EXAMPI~~ 2 Ingredients: Amouy AAC &1 grams Water 40 grams 30 1% MBA 10 grams Darocure 1173 400 ~.cl The resultant gel had a aolids content of 61% by weight and is similar to Exams?Ie 1, except that the saline solution was replaced by water. The polymerization process was thES same as were the properties of the gel.

Ingredients: ount:
AAC 140 grams 2% Saline 60 grams 1% MBA 20 grams _ Darocure 1173 800 ;,ul The procedure of Example l was followed and the resultant transparent gel had a light tack and a solids content of 70% by weight.

Ingredients : Amou:nt 15 AAC 7 0 grams Water 30 grams 1 % MBA 10 grams Darocure 1173 400 ,ul 20 The resultant transparent gel had a light tack and a solids content of 70% b:y weight. This example is similar to Example 3 except that the saline solution was replaced by water. The po:Lymerization process was the same.
EXAMPL1: 5 Inaredients: Amour AAC 70 grams Water 30 crams 30 1% MBA 5 crams Darocure 1173 400 ~~cl The resultant gel had a solids content of 70% by weight and is similar to Example 5, except that the MBA crosslinker was cut in half. The polymerization process was the same and the c~el was essentially clear with a light tack.

E~~J
Ingredients: Amount:
AAC 150 grams 5 2 a Saline 40 grams 1% MBA 20 grams Darocure 1173 800 ,ul The procedure of Example 1 was followed and the 10 resultant transparent gel had a light tack and a solids content of 80% by weight.

Ingredients :, Amount :
15 AAC 80 grams Water 20 grams 1% MBA 10 grams Darocure 1173 400 ~.cl 20 The resultant gel had a ;solids content of 80% by weight and is similar to Example 6 except that the saline solution was replaced by water. The polymerization process was they same as were the physical properties of the gel.
EXAMPLFi 8 Ingredients: Amouy"
AAC 80 crams Water 20 grams 30 1% MBA 5 <firams Darocure 1173 400 ,ccl The resultant gel had a :>olids content of 80% by weight and is similar to Example 7 except that the MBA
35 crosslinker was cut in half. The polymerization process was the same as were t:he physical properties of the gel.

EXAMPLE~~ 9 Ingredients : Amours AAC 90 crams Water 10 crams 1~ MBA 10 crams Darocure 11?3 400 Ncl The gel was prepared as i.n Example 1. The resultant transparent gel had a light tack and a solids content of 90% by weight.
ERAMPI~E 10 Inaredients ; ours AAC 90 grams 2~ Saline 10 grams 1 o MBA 5 grams Darocure 1173 400 ~:l The resultant gel had a solids content of 90% by weight and is similar to Example 9 except that the water was replaced by 2~ saline and the MBA
crosslinker was cut in half. T'he polymerization process was the same and the gel properties were similar.
E~AMPI~E 11 Tngredients: Amoun;~
AAC 180 g~rarns 2~ Saline 20 grams 1~ MBA 20 grams Darocure 1173 800 ,ul The resultant gel had a solids content of 90~ by weight and is similar to Example 10 except that the MBA crosslinker was doubled. The polymerization process was the same as were the gel properties.

The gel of Example 11 was screened far antimicrobial activity using a procedure that was an adaption of the Kirby-Bauer method of testing antibiotics.
The following organisms were transferred to soybean casein digest agar (~cCDA), and incubated at 37~
~ 2°C for 24-28 hours:
10 Pseudomonas aeruginosa, ATCC #9027 Escher.icia coli., ATCC #8739 Klebsiella pneumoniae, ATCC #4352 Staphylococcus aureus, ATC;C # 6538 Enterococcus (Streptococcus) faecalis, ATCC #19433 Candida albicans, ATCC #10231 The test organisms were harvested using 0.9~
saline. Each culture was vortexed vigorously to break up clumps. The titer of each suspension was adjusted 20 to approximately 106 colony formings units per mL
(CFU/mL). The titer of the organism suspensions were confirmed using plate count techniques.
On each test plate, a confluent lawn of organism was prepared by first wetting a sterile cotton swab 25 with the test organism suspension, then streaking on a Muller-Hinton agar (MHAG) plate in three directions with a final sweep around the outside edge of the plate. A total of seven plates were prepared for each set of samples. An additional plate was prepared and 30 incubated as a positive control. A negative sample control and media control were also included.
The gel samples were cut into uniform pieces approximately 5 mm square. Each sample was tested on seven different agar plates. '.the plates were incubated 35 at 37 ~ 2°C until a confluent lawn of the test organism was apparent. The plates were refrigerated at 2-8°C over the weekend until they could be measured.

Average zones of inhibit;ion of each sample and test organism are reported in Table 1.

AVERAGE ZONE OE INHIBITION IN MILLfMETERS
Test Org~an,ism Growp,_A Group B roux C

Escherichia coli 18.1 16.3 15.4 Pseudomanas aeruginosa 17.8 15.3 20.4 Klebsiella pneumoniae 14.4 15.1 14.6 Staphylococcus aureus 16.4 16.7 15.6 Enterococcus faecalis 13.7 16.9 14.2 Candida albicans 0 0 0 15 The inoculating titer of each organism is found in Table 2.

INOCULUM !TITERS
Test Organism Inoculum Titer Escherichia coli 1.3 x 106 cfu/mL

Pseudomonas aeruginosa 5.5 x 106 cfu/mL

Klebsiella pneumoniae 1.2 x 106 cfu/mL

Staphylococcus aureus 2.5 x 106 cfu/mL

Enterococcus faecalis 1.3 x 106 cfu/mL

Candida albicans 3.1 x 106 cfu/mL

It is evident that, except for Candida albicans, the gel of Example 11 showed significant antimicrobial properties as determined by the average zone of 30 inhibition. Although no zones of inhibition were observed on the Candida albicans plates, there was WO 00/1210(! PCT/US99/19441 significantly less growth suz°rounding these test samples indicating some antimicrobial activity.
EXAMP1~E 13 5 To determine whether the: gels of the present invention exhibited any adverse effects on scarified areas of human skin, five test samples were selected and tested. The tests were conducted by an independent testing laboratory using a standard Chamber 10 Scarification Test procedure. Only a summary of the procedure is given in this example.
The following hydrogels were tested: Sample A
(the gel of Example 1), Sample B (the gel of Example 5), Sample C (the gel of Example 6), Sample D (the gel 15 of Example 11) and Sample E (the gel of Example 5 having a minor amount of povidone-iodine, Betadine~
added ) .
The gels were formed into circular pledgets 2 cm in diameter for insertion into a chamber well. Control 20 patches of clean webril material was stamped out and moistened with a control material for comparison purposes.
Ten volunteers were used in the tests. A distinct site of the surface of the forearm of each test 25 subject was selected and designated for contact with each of Samples A-E and controls. The location of the site allocated to one test material as compared to the others varied from subject to subject.
The skin of each volunteE~r was cleansed with 30 alcohol and each site outlined. The skin of each site was scratched with the sharp x>eveled edge of a 30-gauge needle. A newly opened ~;terile needle was used for each participant. Three strokes were made horizontally and three vertically in a cross-hatch 35 formation. Just, enough pressure was applied to the needle to cleave the epidermis without eliciting frank capillary bleeding. Each site was then covered with a chamber containing webril pads that had been moistened with 0.1 ml of sterile physiological saline. The 5 chambers were moored tightly to the sites with wide strips of Hypifix~ Tape. After four hours, the chambers were removed and the scarified sites were examined and graded for adverse changes. These graded sites were then used as a baseline for determining the 10 effects of the hydrogel samples on the sites.
After the baseline value had been established, and using aseptic techniques, the protective covering over the prepared sample chambers was peeled off and the exposed gel pledget was placed directly on the 15 scarified site. The pledget was then covered with a chamber device and moored in place with Hypafix~ Tape.
The test sites on each volunteer were examined daily and graded and the pledget sample was again replaced until being examined the following day.
20 After seventy two hours vthe test was terminated and the data on each test subject compiled and averaged for each test sample. Each site was scored as follows: 1 = No scarification marks or erythema visible; 0.5 = scarification marks visible but no 25 erythema present: 1 = faint erythema along the scarification marks; 2 = moderate to intense erythema adjacent to the scratch marks;' areas between scratch marks unaffected; 3 = confluent, severe erythema filling areas between scratch marks: 4 = severe 30 erythema associated with pustules or blisters.
A mean score of 0.0 to 0.49 was deemed to indicate very low irritating potential. A mean score of 0.5 to 1.49 indicated low irritating potential. A
mean score of 1.5 to 2.49 indicated moderate irritating potential. A mean score of 2.5 to 4.0 indicated high irritating potential.

The resul ts are given below with the physiological saline being used the seline as ba on which to grade the her samples.
ot 1~AN SC~DRES

0 Hour 24 Hour 48 Hour72 Hour Control 0.65 0.55. 0.55 0.50 Sample Aa 0.70 0.75 2.20 0.70 Sample Ab -0.05 -0.05 -0.05 -0.05 1 Sample A' 0.65 0.70 1.15 0.65 Sample Ba 0.60 0.80 0.75 0.55 Sample Bb +0.05 +0.05 +0.05 +0.05 Sample B' 0.65 0.85 0.80 0 .

Sample Ca 0.65 0.55 0.65 0.60 Sample Cb 0.00 0.00 0.00 0.00 Sample C' 0.65 0.55 0.65 0.60 2 Sample Da 0.60 0.60 0.60 0.50 Sample Db +0.05 +0.05 +0.05 +0.05 Sample D' 0.65 0.65 0.65 0.55 Sample Ea 0.65 0.85 0.90 0 Sample E'' 0.00 0.00 0.00 .
0.00 Sample E' 0.65 0.85 0.90 0.65 Mean score Adjustment value core Hour) minus [Baseline control (0 s 3 baseline sample 5 score (0 hour;l]

' Adjusted mean (Adjustment e plus ample mean score valu s score) It can be seen from the above that all samples A-40 E are not significantly diffez°ent from the control in irritation potential, i.e. all., including the saline control, rank in the "low" category. While there was not sufficient data collected to determine the degree of wound healing attributable to the samples, many of 45 the test subjects commented that their scarifications were less painful after the dressings containing Samples A-E were applied. In other words, when samples A-E were applied to the scar:ifications there was a soothing effect observed.
The above description wall enable one skilled in the art to make and use cationic quaternary amine 5 polyacrylate hydrogels as wound dressings. The description is not intended t=o be an exhaustive statement of all embodiments of the invention. Neither are all cationic quaternary amine polyacrylate polymers, which may be prepa3:ed, specifically shown.
10 It will be apparent to one s~:illed in the art that various modifications may be made without departing ,from the scope of the invention which is limited only by the following claims and their functional equivalents.

Claims

What is claimed is:

1. An inherently antimicrobial cationic quaternary amine acrylate polymer of the formula:

wherein n is an integer of 2 to 3; R', R'' and R''' are independently selected from the group consisting of H, C1 to C16 alkyl, aryl, arylamine, alkylamine, alkaryl and aralkyl; X is selected from the group consisting of O and NH; Y- is an acceptable anionic counterion to the N+ of the quaternary amine and m is an integer greater than 50,000.

2. A polymer according to Claim 1 wherein R', R'' and R''' are independently ~>elected from the group consisting of H, C1 to C8 alkyl, phenyl, tolyl and benzyl.

3. A polymer according to Claim 2 wherein R', R'' are methyl and R''' is benzyl.

4. A polymer according to Claim 2 wherein R', R'' and R''' are methyl.

5. A polymer according to Claim 4 wherein X is O.

6. A polymer according to Claim 4 wherein X is NH.

7. A polymer according to Claim 4 wherein Y- is a member selected from the group consisting of Cl-, Br-, HSO4-, and CH3SO4-.

8. A polymer according to Claim 7 wherein Y- is Cl-.

9. A polymer according to Claim 4 wherein n is 2.

10. A polymer according to Claim 4 wherein n is 3.

11. A wound dressing comprising a hydrogel containing from about 15 to 95 percent by weight of an inherently antimicrobial cationic quaternary amine acrylate polymer of the formula:

wherein n is an integer of 2 to 3; R', R'' and R''' are independently selected from the group consisting of H, C1 to C16 alkyl, aryl, arylamine, alkylamine, alkaryl and aralkyl; X is selected from the group consisting of O and NH; Y- is an acceptable anionic counterion to the N+ of the quaternary amine and m is an integer greater than 50,000.

12. A wound dressing according to Claim 11 wherein, in the polymer, R' , R'' and R''' are independently selected from the group consisting of H, C1 to C8 alkyl, phenyl, tolyl and benzyl.

13. A wound dressing according to Claim 12 wherein; in the polymer, R', R'' are methyl and R'' is benzyl.

14. A wound dressing according to Claim 12 wherein, in the polymer, R' , R'' and R''' are methyl.

15. A wound dressing according to Claim 14 wherein, in the polymer, X is O.

16. A wound dressing according to Claim 14 wherein, in the polymer, X is NH.

17. A wound dressing according to Claim 14 wherein, in the polymer, Y- is a member selected from the group consisting of Cl-, Br-, HSO4-, and CH3SO4-.

18. A wound dressing according to Claim 17 wherein, in the polymer, Y' is Cl-.

19. A wound dressing according to Claim 14 wherein, in the polymer, n is 2.

20. A wound dressing according to Claim 14 wherein, in the polymer, n is 3.

21. A wound dressing according to Claim 11 wherein the hydrogel contains between about 61 and 90%
by weight of said cationic quaternary amine polyacrylate polymer:

22. A wound dressing according to Claim 21 wherein the hydrogel contains between about 65 and 75%

by weight of said cationic quaternary amine polyacrylate polymer.

23. A device for the dressing of wounds comprising a substrate having fixedly attached thereto a wound dressing comprising a hydrogel containing from about 15 to 95 percent by weight of an inherently antimicrobial cationic quaternary amine acrylate polymer of the formula:

wherein n is an integer of 2 to 3; R', R'' and R''' are independently selected from the group consisting of H, C1 to C16 alkyl, aryl, arylamine, alkylamine, alkaryl and aralkyl; X is selected from the group consisting of O and NH; Y- is an acceptable anionic counterion to the N+ of the quaternary amine and m is an integer greater than 50,000.

24. A device according to Claim 23 wherein the substrate is a fibrous sheet material embedded in said hydrogel and said hydrogel has opposing surfaces, at least one of which is adapted to cover and be in contact with a wound.

25. A device according to Claim 23 wherein said hydrogel has opposing surface's and said device is an occlusive structure affixed to one surface of said hydrogel with said opposing surface being adapted to cover and be in contact with a wound.

26. A device according to Claim 24 or 25 wherein, in the polymer forming the hydrogel, R', R'' and R''' are independently selected from the group consisting of H, C1 to C8 alkyl, phenyl, tolyl and benzyl.

27. A device according to Claim 26 wherein, in the polymer, R', R'' are methyl and R''' is benzyl.

28. A device according to Claim 26 wherein, in the polymer, R', R'' and R''' are methyl.

29. A device according to Claim 28 wherein, in the polymer, X is O:

30. A device according to Claim 28 wherein, in the polymer, X is NH.

31. A device according to Claim 28 wherein, in the polymer, Y' is a member selected from the group consisting of Cl-, Br-, HSO9-, and CH3S04-.

32. A device according to Claim 31 wherein, in the polymer, Y- is C1-.

33. A device according to Claim 28 wherein, in the polymer, n is 2.

34. A device according to Claim 28 wherein, in the polymer, n is 3.

35. A device according to Claim 23 wherein the hydrogel contains between about 62 and 90% by weight of said cationic quaternary amine polyacrylate polymer.

36. A device according to Claim 35 wherein the hydrogel contains between about 65 and 7.5% by weight of said cationic quaternary amine polyacrylate polymer.

37. A method for treating a wound with an inherently antimicrobial dressing comprising the steps of:
(a) providing a hydrogel containing from about 15 to 95 percent by weight of an inherently antimicrobial cationic quaternary amine acrylate polymer of the formula:

wherein n is an integer of 2 to 3; R' R'' and R''' are independently selected from the group consisting of H, C1 to C16 alkyl, aryl, arylamine, alkylamine, alkaryl and aralkyl; X is selected from the group consisting of O and NH; Y- is an acceptable anionic counterion to the N+ of the quaternary amine and m is an integer greater than 50,000 in a form suitable to cover the wound;
(b) applying said wound dressing to said wound whereby said dressing enhances the serility of the wound environment, absorbs exudate from said wound and retains said wound in a moist condition.

38. A method according to Claim 37 wherein said wound dressing is affixed to device for the dressing of wounds.

39. A method according to Claim 38 wherein said device comprising a substrate of a fibrous sheet material embedded in said hydrogel and wherein said hydrogel has opposing surfaces at least one of which is adapted to cover and be in contact with a wound.

40. A method according to Claim 38 wherein said device is an occlusive structure and wherein said hydrogel has opposing surfaces such that one surface of said hydrogel is affixed to one surface of said occlusive structure with said opposing surface being adapted to cover and be in contact with a wound.

41. A method according to Claim 39 or 40 wherein, in the polymer forming the hydrogel, R', R'' and R''' are independently selected from the group consisting of H, C1 to C8 alkyl, phenyl, tolyl and benzyl.

42. A method according to Claim 41 wherein, in the polymer, R', R'' are methyl and R''' is benzyl.

43. A method according to Claim 41 wherein, in the polymer, R', R'' and R''' are methyl.

44. A method according to Claim 43 wherein, in the polymer, X is O.

45. A method according to Claim 43 wherein, in the polymer, X is NH.

46. A method according to Claim 43 wherein, in the polymer, Y- is a member selected from the group consisting of Cl-, Br-, HSO4-, and CH3SO4-.

47. A method according to Claim 46 wherein, in the polymer, Y- is Cl-.

48. A method according to Claim 43 wherein, in the polymer, n is 2.

49. A method according to Claim 43 wherein, in the polymer, n is 3.

50. A method according to Claim 38 wherein the hydrogel contains between about 61 and 90% by weight of said cationic quaternary amine polyacrylate polymer.

51. A method according to Claim 50 wherein the hydrogel contains between about 65 and 75% by weight of said cationic quaternary amine polyacrylate polymer.