Absorbent hydrogel particles and use thereof in wound dressings

An absorbent dressing for absorbing exudate from a wound is disclosed. The absorbent dressing contains a plurality of dried absorbent hydrogel particles sealed within a porous container. The porous container is non-adherent to the wound, and the hydrogel particles remained sealed within the container after absorbing the wound exudate. In a preferred embodiment, the particles are dried polyacrylonitrile hydrogel particles, and the porous container is in the form of a sachet bag made from nylon, cotton, polyester, polypropylene and the like.

TECHNICAL FIELD 
This invention relates to dried hydrogel particles contained in a porous 
container for absorbing wound exudate, to manage fluid in wounds and/or to 
maintain an optimal healing environment. 
BACKGROUND OF THE INVENTION 
Dermal wound healing is a natural process which occurs whenever there is a 
break in the surface of the skin. An orderly, progressive process begins 
to take place in several stages, commencing with an inflammatory response 
necessary for natural sterilization of the area, clotting, and preparation 
of the wound for its natural progress toward closure. 
The second stage of wound repair primarily involves migration of necessary 
cells to the wound site. These cells, which also appear in an ordered 
sequence during the second stage of healing, include key white cells, 
followed by polymorphonuclear leukocytes and macrophages--all essential to 
initiation of the repair process. These cells serve to clean up the wound 
and to deliver an endogenous mixture of growth factors to the wound site. 
In addition to white cells, fibroblasts from the wound periphery migrate 
to and into the site to deposit collagen, glycosaminoglycans, and other 
extracellular matrix components, providing the basis for granulation 
tissue formation. These macromolecules, in conjunction with capillary 
endothelial cells and new blood vessels, form the new tissue required to 
repair the defect. 
The third stage of dermal wound healing involves proliferation of the cell 
types mentioned above together with subsequent increases in the amount of 
granulation tissue and coverage of the area with new epithelium. 
Throughout the healing process, wounds produce a variety of fluids, 
generally known as wound exudate. The composition and quantity of this 
exudate may differ by wound type and with each stage of the wound's 
healing process. Exudate may vary--consisting primarily of blood and 
serous fluids to highly concentrated protein solutions. In general, wound 
exudate provides the necessary source of growth factors, nutrients and 
cells that are essential to the wound repair process. However, as with 
many biological processes, the amount of wound exudate must be controlled 
because over-production can provide a media for bacterial proliferation or 
lead to maceration of the surrounding healthy tissue. Conversely, 
inadequate types or amounts of wound exudate, or drying of the wound 
fluid, will lead to scab formation and impaired wound healing. 
The control of wound exudate, referred to as moisture control, has become a 
major focus in current wound dressing design. The major categories of 
moist or synthetic wound dressings currently in use are thin films, 
hydrocolloids, hydrogels, and alginates. All of these various types of 
dressings control wound exudate through combinations of absorption, 
moisturization, and moisture permeability. The overall aim of moist wound 
dressings is to maintain the appropriate balance of moisture in the wound 
environment, which is essential to allow the natural wound healing process 
to occur. 
Wound dressings which maintain a moist wound environment range from gels to 
thin films, foams, alginates, and hydrocolloids (see, e.g., Szycher et 
al., J. Biomater. Appl. 7:142-213, 1992). Thin film wound dressings 
consist of synthetic polymeric films which have one side coated with a 
pressure sensitive adhesive. This type of wound dressing has little or no 
absorptive ability and manages moisture primarily by the moisture vapor 
permeability of the polymeric film. Pooling and concentration of wound 
exudate under these dressings is commonly observed. 
Hydrocolloids is a term commonly used to describe a family of wound 
management products consisting of gel forming agents combined with 
elastomers and adhesives attached to a polyurethane film or foam. This 
type of dressing usually has poor moisture vapor permeability, but some 
absorptive capability. These dressings typically absorb wound exudate by 
becoming thicker and forming a gelatinous material over the wound which 
has to be washed from the wound at each dressing change. 
Hydrogel wound dressings are sheet dressings often supplied with an 
impermeable polymeric backing sheet. The presence of the backing sheet 
prevents the partially hydrated hydrogel from dehydrating and drying onto 
the wound bed. The hydrogels are similar to the hydrocolloids in their 
ability to absorb and manage wound exudate. Generally, hydrogel dressings 
do not dissolve into the wound bed as do hydrocolloids. 
Foam dressings are generally manufactured from polymeric materials such as 
hydrophylic polyurethane. These foams contain open cells facing the wound 
surface which serve to absorb wound exudate by a sponge type mechanism. As 
with all sponges, the absorbed exudate is not tightly bound in the foam 
and a certain amount can be "squeezed" from the dressing upon removal. 
Alginates are highly absorbent wound dressings composed of a variety of 
alginic acids extracted from certain species of seaweeds. The addition of 
a calcium salt during processing allows the formation of insoluble fibers 
which can be woven or formed into wound dressings of various sizes and 
shapes. During use, alginate wound dressing typically swell and form a 
soft gel in the wound bed. This gel must be washed from the wound bed at 
each dressing change. 
In addition to the above, EP-A1-0 171 268 discloses a dressing for use in 
deep wounds which comprises small pieces of absorbent polyurethane foam 
contained within a porous bag or sachet. In a similar manner, EP-A1-0 575 
090 discloses products suitable for absorbing wound exudate comprising 
particles of alginate or alginic acid enclosed in perforated bags. 
Despite the wide variety of wound dressings available, chronic wounds are 
still a serious medical situation and there is a need for advanced wound 
care dressings which manage the moist wound environment. This includes the 
need for moisture controlling and absorbing wound dressings which do not 
leave a residue in the wound bed and which retain fluid when removed. The 
present invention fulfills these needs and provides further related 
advantages. 
SUMMARY OF THE INVENTION 
Briefly stated, this invention generally relates to the management of the 
wound environment by the absorption of excess exudate by dried hydrogel 
particles. In particular, the application of such absorbent dried hydrogel 
particles, contained in a non-adherent porous pouch or sachet, allows easy 
application and removal of the absorbent particles from the wound bed, as 
well as easy access of the particles to the wound exudate. Hydrogels are 
cross-linked water swollen polymers having a water content ranging from 
30% to 90% or greater depending on the type of polymer used. 
In one aspect of the invention, dried hydrogel particles are prepared by 
base hydrolysis of polyacrylonitrile aquagel followed by neutralization 
and drying essentially as disclosed in U.S. Pat. No. 4,943,618 to Stoy et 
al (hereby incorporated by reference). The dried hydrogel particles are 
packaged in sachets formed by heat sealing porous sheets of low density 
polyethylene or similar polymeric material. The polyethylene mesh is such 
that the openings are large enough to allow fluid transfer, but small 
enough to contain the absorbent particles. In addition, the amount of 
absorbent particles is such that, if the maximal amount of fluid is 
absorbed by the particles, the particles do not cause rupture of the 
sachet. Sachets formed in this manner absorb saline at 2-50 times their 
weight. In a preferred embodiment of the invention, the particles absorb 
about 10-30 times their weight in saline. 
In another aspect of the invention, absorbent dried hydrogel particles are 
sealed in sachets formed from an acceptable medical grade of nylon mesh. 
Sachets may also be formed from any type of porous material such as 
non-woven or woven cotton gauze, polyester mesh, polypropylene and 
polyvinyl acetate. 
The non-adherent porous pouch or sachet containing the absorbent dried 
hydrogel particles of this invention may comprise multiple parts or 
pockets. For example, these could comprise dressings with two rows of two 
individual sachets, or one row with multiple individual linked sachets. 
The sizes of the individual sachets are chosen to fit within specific 
sizes or types of wounds. 
In another aspect of this invention, the non-adherent porous pouch or 
sachet containing the absorbent dried hydrogel particles of this invention 
may comprise part of a larger wound dressing. In this aspect, the 
non-adherent porous pouch or sachet containing the absorbent dried 
hydrogel particles would serve as the part of a wound dressing which would 
absorb wound exudate, while other parts would serve to keep the sachet in 
place and to protect the wound. 
The absorbent dried hydrogel particles can take various forms such as 
granules, cylindrical pellets, spheres, or spheroids. Such particles can 
be ground to a fine powder and still contained within the sachet as long 
as the perforations in the bag are smaller than the diameter of the 
particles contained therein. 
In another aspect of the invention, absorbent hydrogel particles can be 
ground to a fine powder, mixed with binders and plasticizers and pressed 
into sheets. Such sheets can then be encased in porous mesh to form 
pouches or sachets. Although the initial size of the powdered absorbent 
dried hydrogel particles prepared in this aspect of the invention may be 
smaller than the perforations in the bag when they are dry, upon 
absorption of wound exudate, the hydrogel particles swell such that their 
diameter is greater than the perforations in the pouch material. The small 
size of the absorbent dried hydrogel particles in powdered from results in 
very rapid fluid absorption. 
The combination of the absorbent dried hydrogel with a variety of other 
materials (binders) and plasticizers forms a matrix in which the absorbent 
is evenly distributed. The matrix allows moisture to wick rapidly to the 
interior of absorbent by exposing the maximal surface of the absorbent 
particle to moisture. This allows a much higher rate of absorption 
associated with high surface area while obviating the difficulties of 
handling/packaging fine absorbent powders. The material may be molded to 
almost any shape. 
In another aspect of the invention, the absorbent particles of the 
invention may contain or release wound healing agents or nutrients which 
wound aid the healing process or maintain an optimal healing environment. 
Such agents would be, for example, growth factors, antiseptic and 
anti-microbial agents, vitamins, and/or micronutrients such as copper or 
zinc. The absorbent particles of the invention may also contain or release 
agents to control odor in the wound or to control infection in the wound. 
Examples would be activated charcoal, antibiotics and antifungals. 
Other aspects of this invention will be apparent from the following 
detailed description and attached drawings.

DETAILED DESCRIPTION OF THE INVENTION 
As mentioned above, this invention is generally directed to management of 
the wound environment by absorption of excess exudate with absorbent dried 
hydrogel particles. In a preferred aspect of this invention the absorbent 
dried hydrogel particles of the invention are prepared by base hydrolysis 
of polyacrylonitrile aquagel followed by neutralization and drying 
essentially as described in U.S. Pat. No. 4,943,618 to Stoy et al. Aquagel 
is a solid form of polyacrylonitrile (PAN) formed by extrusion of a 15% 
solution of PAN dissolved in 55% NaSCN into a large excess of distilled 
water. This extrusion process results in the formation of apparently solid 
pellets of PAN containing 69-75% water. This form of PAN, termed an 
aquagel, is composed of alternating domains of "crystalline" PAN and 
"amorphous" domains in which the PAN chains are held apart by water filled 
voids. 
One preferred dried hydrogel particle of this invention is a base 
hydrolysis product of PAN aquagel which absorbs approximately 50-60 times 
its weight in excess saline. The general preparation procedure is 
summarized as follows: 
______________________________________ 
Aquagel Noodles, or 
PAN Source Pellets, or beads 
______________________________________ 
NaOH Concentration 4.5% 
Temperature 19-23.degree. C. 
Quench Point, Wt.sub.final /Wt.sub.initial 11.9-12.0 
Hydrolysis Time 115 hours 
Salt Form Ammonium Salt 
______________________________________ 
The aquagel pellets are incubated in the NaOH solution under the above 
conditions. The extent of the hydrolysis of the nitrile groups in the 
"amorphous" domains is monitored by the weight gain of the aquagel as 
hydrolysis results in polymer structures which swell in an aqueous 
environment. This swelling is monitored as a ratio of the weight at time t 
(Wt.sub.time t,)to the initial weight (Wt.sub.initial). The reaction 
quench point is the swelling or weight gain ratio as described above. 
After the desired quench point swelling of 11.9 to 12.0 was achieved, the 
reaction was terminated by the addition of cold dilute sulfuric acid. The 
hydrogel pellets were washed extensively with distilled water followed by 
soaking in 12% ammonium bicarbonate solution. The resultant pellets were 
placed in a 60.degree. C. oven until dried. 
Another preferred dried hydrogel product of this invention is prepared by a 
procedure similar to the above, except that the swelling target quench 
factor is 6.0. The general preparation procedure is summarized as follows: 
______________________________________ 
Aquagel Noodles, or 
PAN Source Pellets, or Beads 
______________________________________ 
NaOH Concentration 4.5% 
Temperature 30.0-31.0.degree. C. 
Quench Point, Wt.sub.final /Wt.sub.initial 6.0 .+-. 0.2 
Hydrolysis Time 29-30 hours 
Salt Form Ammonium Salt 
______________________________________ 
After the desired quench point swelling of 6.0 is achieved, the reaction is 
terminated by the addition of cold dilute sulfuric acid. The hydrogel 
pellets are washed extensively with distilled water followed by soaking in 
12% ammonium bicarbonate solution. The resultant pellets are placed in a 
60.degree. C. oven until dried. 
Other embodiments of the invention are absorbent dried hydrogel particles 
prepared by the above procedures to quench point swelling of 4 to 8. 
The shape and size of the starting aquagel particles determine the shape 
and size of the dried hydrogel particles of this invention. Such absorbent 
dried hydrogel particles can take various forms, such as granules, 
cylindrical pellets, spheres, and spheroids. 
In a preferred embodiment of this invention, the dried hydrogel particles 
are small cylinders approximately 0.5-2 mm in length with a diameter of 
approximately 1 mm. A more preferred embodiment is small spherical 
particles 0.5-2 mm in diameter. 
Other hydrogels can also be used in this invention to form absorbent dried 
hydrogel particles. Examples of hydrogels which could be dried are those 
prepared from polyacrylic acids, polyacrylamides, poly-2-hydroxyethyl 
methacrylate, poly ethyl methacrylate, poly-propylene glycol methacrylate, 
poly-N-vinylpyrrolidone, poly methyl methacrylate, poly glycidyl 
methacrylate, poly-glycol methacrylate, absorbent silicones, and absorbent 
polyurethanes. The process of drying and forming absorbent dried hydrogel 
particles from the above hydrogels are known to those skilled in this 
field. 
Preferred embodiments of this invention are dried hydrogel particles 
encased in square, rectangular, circular, or oval porous polyethylene 
sachets. Such porous sachets are divided by heat seals into multiple 
individual pouches containing dried hydrogel particles depending on the 
size of the sachet. A description of preferred sizes and shapes for sachet 
dressings is shown below. 
______________________________________ 
5 in .times. 5 in 
Two rows of two pouches each 
4 in .times. 4 in Two rows of two pouches each 
3 in .times. 3 in Two rows of two pouches each 
2 in .times. 2 in Two rows of two pouches each 
1.5 in .times. 3 in One row of two pouches 
0.75 in .times. 6 in One row of three pouches 
______________________________________ 
The individual sachet s of this invention can be manufactured with either 
square corners or round corners. In a preferred embodiment the smaller 
sizes of sachets of this invention could also include a "tail" or handle 
composed of the same or similar porous polyethylene mesh. Such a handle 
serves to facilitate removal of the absorbent sachet from the wound bed. 
In addition to porous polyethylene and nylon, other materials may also be 
used to form the sachet pouches of this invention. Examples of preferred 
materials are shown below: 
______________________________________ 
Woven and non-woven polypropylene 
porous Low density polyethylene 
Woven and non-woven polyester and derivatives 
Woven and non-woven nylon 
Woven and non-woven rayon 
Woven and non-woven cotton 
Woven and non-woven other materials 
Woven and non-woven blends of the above 
LDPE laminates of the above 
Porous PTFE laminates of the above 
Polyethylene oxide gels 
Thin hydrogel sheets 
Other moisture transparent polymer sheets 
Other moisture transparent egls 
LDPE mesh 
other polymeric mesh 
hydrophilic polyurethanes 
______________________________________ 
In another embodiment, the absorbent dried hydrogel particles encased in 
porous polyethylene or nylon pouches absorb an amount of wound exudate in 
24 hours such that the wound exudate would not migrate beyond the bounds 
of the dressing. 
In another embodiment of this invention, the absorbent hydrogel particles 
are ground to a fine powder, mixed with binders and plasticizers and 
pressed into sheets or other shapes such as spheres. Such sheets are then 
encased in the porous mesh sachets of the invention. The small size of the 
dried hydrogel particles in powdered form results in very rapid fluid 
absorption while the binders and plasticizers serve to maintain the 
powdered hydrogel within the porous sachet. 
Preferred binding agents and plasticizers which can be mixed with the 
powdered dried hydrogel particles are shown below. 
______________________________________ 
Binders Plasticizers 
______________________________________ 
Sucrose Glycerin 
Carageenan PEG 200 
Sodium and Calcium Alginates PEG 400 
Gum Arabic PEG 600 
Corn starch Propylene Glycol 
Bovine Serum Albumin Sorbitol 
Fumed Silica 
Ethyl cellulose 
Methyl cellulose 
______________________________________ 
Other binders and plasticizers within the scope of this invention are shown 
below. 
______________________________________ 
Binders Plasticizers 
______________________________________ 
Other Sugars Other PEGs 
Other Gums Polyethylene oxide solutions 
Other Starches Polyethylene oxide gels 
Other Proteins Tripropylene glycol 
Starch co-polymers Corn oils 
Gelatins Vegetable oils 
Pectins Mineral oils 
Carbomers, carbopols 
Polyhydroxyethyl methacrylate 
Aloe Vera 
Agars 
______________________________________ 
In another embodiment of this invention, the non-adherent porous pouch or 
sachet containing the absorbent dried hydrogel particles of this invention 
may comprise part of a larger wound dressing. In this aspect, the 
non-adherent porous pouch or sachet containing the absorbent dried 
hydrogel particles would be attached to a sheet wound dressing. Such 
combination wound dressings are commonly called "island" dressings. The 
non-adherent porous pouch or sachet containing the absorbent dried 
hydrogel particles would serve to absorb wound exudate while the upper 
layer would serve to keep the sachet in place over the wound and to 
protect the wound from the environment. Examples of materials which can be 
used for island dressing outer layers are the following: 
______________________________________ 
Polyurethane foams (open and closed cell) 
Hydrophilic polyurethane foams (open and closed cell) 
Other polymeric foam materials (open and closed cell) 
Porous PTFE laminates of polymeric foams 
Porous PTFE laminates of woven or non-woven nylon 
Porous PTFE laminates of woven or non-woven polyester and derivatives 
Porous PTFE laminates of woven or non-woven rayon 
Porous PTFE laminates of woven or non-woven polypropylene 
Porous PTFE laminates of low density polyethylene 
Polyurethane sheets 
Polyester sheets 
Polyethylene sheets 
Polypropylene sheets 
Laminates of various rubbers and woven or non-woven nylon 
Laminates of various rubbers and woven or non-woven nylon 
Laminates of various rubbers and woven or non-woven polyester and 
derivatives 
Laminates of various rubbers and woven or non-woven polypropylene 
Laminates of various rubbers and low density polyethylene 
Laminates of various rubbers and woven or non-woven rayons 
Laminates of various rubbers and other fabrics 
Laminates of various rubbers and polymeric foams 
Spandex 
Laminates of various materials on spandex 
______________________________________ 
In another embodiment of this invention, the non-adherent porous pouch or 
sachet containing the absorbent dried hydrogel particles of this invention 
may be coated with an acceptable medical grade adhesive to maintain the 
sachet in the wound. 
The following examples are offered by way of illustration, and not by way 
of limitation. 
EXAMPLES 
The examples which follow illustrate the preparation, characterization and 
utility of certain exemplary embodiments of the present invention. 
Example 1 
Preparation of Highly Absorbent Dried Hydrogel Particles By Base Hydrolysis 
of Polyacrylonitrile 
One type of dried hydrogel particles of the invention are prepared by base 
hydrolysis of polyacrylonitrile aquagel (to a quench factor of 6.0) 
followed by neutralization and drying essentially as described in U.S. 
Pat. No. 4,943,618 to Stoy et al. 
Aquagel-15 pellets (2000 g) were rinsed and drained of excess water and 
then transferred to a plastic basket lined with polypropylene mesh. 
Approximately 20 pellets (0.1550 g) were blotted dry with a paper towel, 
weighed on an analytical balance and transferred to a probe container 
fabricated from a capped 15 ml Teflon centrifuge tube that had been 
uniformly pierced with 1/8" holes. The basket was placed into a Nalgene 
tank (50 L) containing a solution of 1010 g NaOH in 21.28 kg of deionized 
H.sub.2 O at 30.degree. C. The temperature of the reaction mixture was 
maintained at 30.degree. C. by continuous recirculation of the sodium 
hydroxide solution through a stainless steel coil immersed in a 30.degree. 
C. water bath using a small pump (10 gpm). The probe container was 
immersed in the sodium hydroxide solution and the timer was started. After 
approximately 30 minutes in the sodium hydroxide solution the pellets had 
turned a deep burgundy color. Monitoring of the probe weight was begun 
after a reaction time of approximately 20 hours. This was performed by 
removing the probe container from the sodium hydroxide solution, noting 
the time, blotting the pellets dry on a paper towel and then weighing the 
pellets on an analytical balance. When the pellets had reached a six-fold 
(6.0.+-.0.2) increase in weight, the reaction was quenched by addition of 
a solution of 1728 g concentrated H.sub.2 SO.sub.4 in 5174 g deionized 
water, which had been pre-equilibrated to 4.degree. C. The quench reaction 
was allowed to proceed for 4 hours whereby the red color had disappeared 
from the center of the pellets when cut in half. The quench solution was 
drained off and the pellets were washed with deionized H.sub.2 O with 
continuous overhead stirring until the pH was .gtoreq.5.0. The washed 
pellets were then added to a solution of 648 g of NH.sub.4 HCO.sub.3 in 
4.8 kg deionized H.sub.2 O in a 50 L Nalgene tank and the neutralization 
reaction was allowed to proceed overnight at room temperature. After 
standing overnight the pellets had absorbed all of the liquid. The pellets 
were rinsed quickly with deionized H.sub.2 O and then transferred to Pyrex 
trays for drying at 60.degree. C. in a convection oven. Yield: 776 g of 
dried hydrogel pellets. A representative cylinder shaped highly absorbent 
hydrogel particles is shown and described in FIG. 1. 
Another type of dried hydrogel particles of the invention are prepared by 
base hydrolysis of polyacrylonitrile aquagel to a quench factor of 12.0. 
Aquagel-15 pellets (1000 g) were rinsed and drained of excess water and 
then transferred to a plastic basket lined with polypropylene mesh. 
Approximately 22 pellets (0.1654 g) were blotted dry with a paper towel, 
weighed on an analytical balance and transferred to a probe container 
fabricated from a capped 15 ml Teflon centrifuge tube that had been 
uniformly pierced with 1/8" holes. The basket was placed into a Nalgene 
tank (50 L) containing a solution of 1010 g NaOH in 21.28 kg of deionized 
H.sub.2 O at 35.degree. C. The temperature of the reaction mixture was 
maintained at 35.degree. C. by continuous recirculation of the sodium 
hydroxide solution through a stainless steel coil immersed in a 35.degree. 
C. water bath using a small pump (10 gpm). The probe container was 
immersed in the sodium hydroxide solution and the timer was started. After 
approximately 30 minutes in the sodium hydroxide solution the pellets had 
turned a deep burgundy color. Monitoring of the probe weight was begun 
after a reaction time of approximately 20 hours. This was performed by 
removing the probe container from the sodium hydroxide solution, noting 
the time, blotting the pellets dry on a paper towel and then weighing the 
pellets on an analytical balance. When the pellets had reached a 
twelve-fold (12.0.+-.0.2) increase in weight, the reaction was quenched by 
addition of a solution of 1728 g concentrated H.sub.2 SO.sub.4 in 5174 g 
deionized water, which had been pre-equilibrated to 4.degree. C. The 
quench reaction was allowed to proceed for 4 hours whereby the red color 
had disappeared from the center of the pellets when cut in half The quench 
solution was drained off and the pellets were washed with deionized 
H.sub.2 O with continuous overhead stirring until the pH was .gtoreq.5.0. 
The washed pellets were then added to a solution of 324 g of NH.sub.4 
HCO.sub.3 in 2.4 kg deionized H.sub.2 O in a 50 L Nalgene tank and the 
neutralization reaction was allowed to proceed overnight at room 
temperature. After standing overnight the pellets had absorbed all of the 
liquid. The pellets were rinsed quickly with deionized H.sub.2 O and then 
transferred to Pyrex trays for drying at 60.degree. C. in a convection 
oven. Yield: 325 g of dried hydrogel pellets. 
Example 2 
Preparation of Highly Absorbent Dried Hydrogel Articles Containing 
Micronutrient Copper 
Another dried hydrogel product of this invention was prepared by a 
procedure similar to example 1 with the quench factor of 6.0 except than a 
source of micronutrient copper was added to the hydrogel particles before 
drying. 
Pellets were prepared from Aquagel-15 as described above except that the 
pellets were not neutralized with ammonium bicarbonate. The quenched and 
washed "acid-stage" pellets of hydrogel were stored at room temperature in 
deionized H.sub.2 O. To 121 g of the acid-stage pellets was added a 
solution of 8.5 g glycyl-L-histidyl-L-lysine copper complex and 81 g 
ammonium bicarbonate in 600 g deionized H.sub.2 O. This mixture was 
allowed to stand overnight at room temperature whereby all of the liquid 
had been absorbed. The blue pellets were transferred to Pyrex drying trays 
and dried at 60.degree. C. in a convection oven. Yield: 92.4 g. 
Example 3 
Polyethylene Sachet Containing Highly Absorbent Hydrogel Particles 
A Polyethylene sachet containing highly absorbent hydrogel particles is 
shown and described in FIG. 2. The sachet outer material is a low density 
polyethylene mesh (LDPE). 
Sheets of porous polyethylene mesh were cut to the desired sizes and three 
sides were heat sealed to form a pouch with one open side. The necessary 
weight of dried hydrogel particles were weighed out and added to the 
sachet and the top portion of the sachet heat sealed. Representative 
sachet dressings of the following dimensions were prepared: 4 inch X 4 
inch (4 packets), 3 inch X 3 inch (4 packets), 4.5 inch X 1 inch (2 
packets, 1 empty), and 0.65 inch X 4.5 inch with 3 packets. 
Example 4 
Saline Absorption By a Polyethylene Sachet Containing Highly Absorbent 
Hydrogel Particles 
One method to demonstrate utility of absorbent wound dressings of this 
invention is to determine the amount of 0.9% NaCl (Saline) which is 
absorbed by the dressing over time. Saline absorption can be determined by 
placing the sample in a large excess of 0.9% NaCl at room temperature. 
Absorption is determined by the weight gain of the invention after removal 
of surface moisture. Samples are incubated in the saline solution for up 
to 24 hours or until a constant weight gain is recorded. Milliliters of 
saline absorbed is calculated by subtracting the initial weight of the 
dressings from the weight at the specified time point. 
Representative sachet dressings of the following dimensions were prepared 
as described in Example 2 and tested: 4 inch X 4 inch (4 packets), 3 inch 
X 3 inch (4 packets), 4.5 inch X 1 inch (2 packets, 1 empty), and 0.65 
inch X 4.5 inch with 3 packets. 
The time course of saline absorption under the test conditions for all 
sizes of sachets containing a dried hydrogel is shown in FIG. 3. The 
maximal absorption ranged from about 5 to 50 milliliters. The dressings 
absorbed 20-25% of their maximal absorption within the first 5 minutes, 
the first time point taken. 
Example 5 
Sachet Containing Absorbent Hydrogel Particles Combined With Binding Agents 
and Plasticizers 
An absorbent hydrogel sheet was prepared by first mixing 10.00 g finely 
ground dried hydrogel material of Example 1 with 6.01 g powdered 
amylose-amylopectin (corn starch). These blended powders were then 
combined with 11.99 g glycerin with stirring. After a homogenous mixture 
was obtained a fraction of the slurry was sandwiched between two layers of 
silicone treated paper and cured at 75.degree. C. for 25 minutes. 
The resultant wafer was then weighed and heat sealed in a non-woven nylon 
mesh bag large enough such that upon swelling of the polymer it would not 
be full. The sample was then immersed in 0.9% NaCl. Weights after 
squeezing out entrapped water were obtained over time. Weights minus the 
bag weights were used for data analysis. See FIG. 4 which shows the saline 
absorption over time. 
A further absorbent hydrogel sheet was prepared by first mixing 6.92 g 
finely ground dried hydrogel material of Example 1 with 6.92 g powdered 
sucrose. These blended powders were then combined with 4.45 g glycerin 
with stirring. After a homogenous mixture was obtained a fraction of the 
slurry was sandwiched between two layers of silicone treated paper and 
cured at 75.degree. C. for 2.5 hours. 
The resultant wafer was then weighed and heat sealed in a non-woven nylon 
mesh bag large enough such that upon swelling of the polymer it would not 
be full. The sample was then immersed in 0.9% NaCl. Weights after 
squeezing out entrapped water were obtained over time. Weights minus the 
bag weights were used for data analysis. See FIG. 5 which shows the saline 
absorption over time. 
Example 6 
Sachet Containing Absorbent Hydrogel Particles Combined With Binding Agents 
and Plasticizers 
A 7 g absorbent layer composed of dried hydrogel particles approximately 2 
inches square by 1/16 inches high was prepared as described in Example 5. 
It was then heat sealed between two sheets of porous non-woven nylon 
material approximately 2 and 1/2 inches square to form a sachet or pouch. 
A 4 and 1/2 inch square sheet of polyurethane foam was coated with 2 mil. 
of medical grade adhesive. The sachet described above was adhered to the 
adhesive coated foam concentrically and covered concentrically with a 3 
and 1/2 inch square sheet of LDPE mesh. Silicone treated release paper was 
then applied to the adhesive side and the dressing was packaged. This 
dressing is illustrated in FIG. 6. 
From the foregoing, it will be appreciated that, although specific 
embodiments of the invention have been described herein for purposes of 
illustration, various modifications may be made without deviating from the 
spirit and scope of the invention. Accordingly, the invention is not to be 
limited except as by the appended claims.