Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Reexamination Certificate
1998-09-17
2001-01-30
Clardy, S. Mark (Department: 1616)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
C604S304000, C604S308000, C602S041000, C602S042000, C602S043000, C602S046000, C602S048000, C602S052000, C602S053000, C602S056000
Reexamination Certificate
active
06180132
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydrogel wound dressing and a method of making and using the same. More particularly, the present invention relates to a flexible hydrogel wound dressing which is highly absorptive, contours to a wound site and maintains a wound in a moist state to promote healing thereof and the method of producing and using the same.
BACKGROUND OF THE INVENTION
The treatment of draining wounds is a problem in the medical profession. Wound exudate such as blood, serum and purulent matter from a draining wound can lead to bacterial growth and delayed healing if not treated properly. Often times it is difficult to maintain wounds free of such wound secretions to allow for healing. Another concern in treating such draining wounds is that some believe that allowing a wound to heal in a slightly moist state may actually accelerate healing. Accordingly, the medical profession desires a means for maintaining draining wounds in a clean, moist protected state.
Currently in an attempt to meet such wound treatment needs there are wound exudate absorption compositions which are comprised of hydrogel materials in powder form. One example of such a powder material includes dextranomer beads. Dextranomer beads are hydrophilic spherical beads which are applied to a wound to absorb wound exudate. Disadvantages noted in using materials in powder form include difficulty in achieving even application, difficulty with lumping and clumping of the material after application and difficulty in removing the material from a wound site without damaging newly formed tissues in the wound.
U.S. Pat. No. 4,226,232 discloses the blending of a hydrogel material with a liquid curing agent such as polyethylene glycol prior to introducing the material to a wound. A difficulty observed in the use of this material is that it can not be sterilized by irradiation due to the formation of free radicals within the gel material. These free radicals so formed within the gel material cause an instability of the hydrogel product thereby shortening the shelf life thereof.
U.S. Pat. No. 5,059,424 discloses a wound dressing comprising a backing member with an adhesive layer and a hydrogel material layer of 15-30% polyhydric alcohol, 8-14% iso phorone diisocyanate prepolymer, 5-10% polyethylene oxide-based diamine, 0-1% salt and the balance water. Difficulties associated with the use of this wound product includes the limitation of not being able to cut the dressing to a size appropriate for the particular wound site and still have the backer intact. Additionally, the hydrogel material disclosed in this patent lacks the necessary strength to be used and removed in tact without the added support of the backer material.
The need exists for a sterile wound dressing which provides a size appropriate protective covering for a draining wound capable of absorbing exudate from the wound. It is also desirable to have a wound dressing suitable to protect a wound from debris and foreign matter capable of contaminating the wound. It is also desirable to have a wound dressing which cushions a wound from pressure. It is also desirable to have a wound dressing which does not adhere to new tissue forming in a wound. It is also desirable to have a wound dressing which maintains a wound in a slightly moist state to promote healing.
SUMMARY OF THE INVENTION
The present invention relates to a transparent, insoluble hydrogel wound dressing capable of absorbing exudate from a draining wound without becoming adhered thereto. The subject wound dressing maintains a wound in a slightly moist state to promote healing of the wound while retaining its overall strength to allow for removal thereof in a unitary fashion.
The hydrogel wound dressing of the present invention is a polyurethane hydrogel material comprising polyurethane prepolymer, deionized water, glycols, polyalkyldiamine and optionally an antimicrobial and/or a bacteriostatic agent.
The method of producing the hydrogel material of the present invention involves hydrolysis and addition reactions to produce a three-dimensional cross-linked polyurethane hydrogel as described in more detail below. The resultant polyurethane hydrogel material is blended and cast molded to allow for complete gelatinization thereof in less than 180 minutes at room temperature. Gelatinization preferably begins within 30 to 40 minutes. The subject bubble-free hydrogel wound dressing is then optionally subjected to temperatures below 0° C. to remove excess water prior to packaging and sterilization using radiation sterilization or other suitable sterilization technique known to those skilled in the art prior to distribution.
DETAILED DESCRIPTION OF THE INVENTION
The polyurethane hydrogel wound dressing of the present invention is capable of absorbing moisture from a wound site until the overall composition comprises approximately 70 percent to 99 percent water or fluid. The subject non-adhesive hydrogel dressing provides for moist wound healing, absorbs wound exudate, allows for relatively fewer dressing changes, allows for easy removal with no trauma to a wound, protects a wound from contamination and minimizes wound odor.
The polyurethane hydrogel material of the present invention is generally produced by the formation of carbamate (urethane) linkages by the reaction of isocyanates with alcohols and by the formation of urea linkages through the reaction of isocyanates with water. These reactions are achieved by blending a polyoxyethylene-rich isophorone diisocyanate terminated oligomer, i.e., a polyurethane prepolymer, with a polyetherdiamine chain modifier having a predominately polyethylene oxide backbone and an approximate molecular weight between 500 and 5,000, deionized water, propylene glycol and polyethylene glycol in accordance with the following reactions:
STEP 1:
O═C—N—R
1
—N═C═O+2R
2
OH→R
2
OOC—HN—R
1
—NH—COOR
2
+O═C—N—R
1
—N═C═O
Prepolymer+Alcohol Polyurethane+Unreacted Prepolymer
STEP 2:
R
1
—NH—COOR
2
+O═C═N—R
1
—N═C═O+2H
2
O+R
1
ONH
2
→R
1
NH
2
+2CO
2
+O═C═N—R
1
—N═C═O+R
1
—NH—COOR
2
Polyurethane+Unreacted Prepolymer+Water+Amine Accelerator→Polyamine(unstable intermediate)+Carbon Dioxide+Unreacted Prepolymer+Polyurethane
STEP 3:
R
1
—NH—COOR
2
+O═C═N—R
1
—N═C═O+2R
1
NH
2
→R
1
HNOC—HN—R
1
NH—CONHR
1
+R
1
—NH—COOR
2
Polyurethane+Unreacted Prepolymer →Polyurea (stable)+Polyurethane+Polyamine (unstable intermediate)
wherein the R
1
groups may be the same or different selected from the group consisting of C
1-12
alkyl repeating groups such as for example methyl, ethyl or propyl but preferably propyl for increased strength and stability; C
1-12
mono- or poly-hydroxyalkyl repeating groups such as for example hydroxymethyl or dihydroxypropyl but preferably dihydroxypropyl for increased strength and stability; C
1-12
acyl repeating groups such as for example acetyl or proprionyl but preferably proprionyl for increased strength and stability; C
1-12
alkoxyalkyl repeating groups such as for example methoxyethyl or ethoxypropyl but preferably ethoxypropyl for increased strength and stability; C
1-12
aminoalkyl repeating groups such as for example aminomethyl or aminopropyl but preferably aminopropyl for increased strength and stability; C
1-12
acylaminoalkyl repeating groups such as for example acetylaminomethyl or proprionylaminomethyl but preferably prorionylaminomethyl for increased strength and stability; C
1-12
oxyalkyl repeating groups such as but not limited to oxyethylene, oxypropylene or oxybutylene but preferably oxyethylene and/or oxypropylene to increase clarity, such repeating units having an average molecular weight of about 7,000 to about 30,000 capped with aromatic, aliphatic or cycloaliphatic isocyanates, diisocyanates or polyisocyanates, but most preferably diisocyanate- or polyisocyanate-capped repeating units as described a
Earhart Stephen B.
Fiehler William R.
Huang Yeong Hua
Brown, Rudnick, Freed & Gesmer, P.C.
Clardy S. Mark
Leonardo Mark S.
Sherwood Services AG
Williamson Michael A.
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