Wound dressing and manufacture thereof

Details Wound dressing and manufacture thereof Wound dressing and manufacture thereof

1999-03-03

2000-11-28

Clardy, S. Mark

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Web, sheet or filament bases; compositions of bandages; or...

A61K 970, A61F 1300

Patent

active

061532142

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to improvements in hydrogel sheet dressings, that is to say dressings in the form of a gel sheet, namely a sheet comprising a major proportion of water and a minor proportion of polymeric material, and in methods of manufacturing the same.


BACKGROUND ART

Various types of hydrogel sheet dressing are known and are available commercially. The properties of two such dressings are reported by S Thomas in J. Wound Care, 1993, 2, 176. Hydrogels have been recommended for use as wound contact layers. Desirably, a wound contact layer should be non-adherent, conformable and permeable to aqueous liquids such as wound exudate and should maintain its integrity during use.


DISCLOSURE OF THE INVENTION

According to the invention there is provided a method of manufacturing a wound dressing in the form of a gel sheet, characterised in that a textile material comprising at least 50 percent by weight of a gel-forming fibre is thoroughly wetted with an aqueous liquor and then pressed, thereby forming the gel sheet.
The textile material may consist essentially of the gel-forming fibre, or it may contain in its body or as backing layer reinforcement in the form of fibre or scrim which is not gel-forming. The presence of such reinforcement assists in maintaining dimensional stability through the pressing step. Textile materials which comprise at least 75 or at least 90 percent by weight of the gel-forming fibre may be preferred.
The textile material may be a bonded carded fibre web or a knitted or woven fabric, but it is preferably a nonwoven fabric such as a spunlaced or needled fabric. The basis weight of the textile material is preferably in the range from 20 to 1000, more preferably 50 to 250, g/m.sup.2. The textile material may additionally comprise solid material in powder form, for example a hydrophilic or superabsorbent polymer.
Suitable gel-forming fibres include alginate-based fibres, in particular calcium alginate fibres, carboxymethylated cellulose (CMC) fibres such as those disclosed in U.S. Pat. No. 4,579,943 and WO-A-93/12275, in particular carboxymethylated lyocell fibres, and fibres of cross-linked polymers based on acrylic acid such as those disclosed in EP-A-0,269,393, EP-A-0,397,410 and WO-A-94/04724. For calcium alginate fibres, fibres of the high-M type (e.g. containing from 50 to 75 percent by weight mannuronic acid) may be preferred. Other examples of gel-forming fibres include fibres based on pectin, chitosan, hyaluronic acid and other polysaccharides derived from gums. Blends of gel-forming fibres may be used.
The aqueous liquor may be water but is preferably a saline solution, for example containing from 0.1 to 5.0, often about 0.9, percent by weight sodium chloride, preferably physiological saline. If desired, the aqueous liquor may contain ions which exhibit physiological activity, for example silver or zinc cations. A wound dressing produced by the method of the invention may have hypotonic or hypertonic properties, depending on its salt content. The aqueous liquor may be an aqueous alcohol, for example aqueous ethanol, to permit greater control in the wetting and pressing steps. The aqueous liquor may additionally comprise one or more dissolved or dispersed substances which it is desired to incorporate into the dressing. Examples of such substances include conventional substances used as preservatives, humectants such as propylene glycol, antimicrobial agents, pharmaceutical agents, analgesics, non-stick compositions such as silicore emulsions, wound-healing agents, odour-absorbing agents and fragrances. An aqueous liquor which comprises from 5 to 25 percent by weight propylene glycol may confer the benefits both of process control and of the incorporation of this substance in the dressing.
The textile material may conveniently be wetted with the aqueous liquor by immersion therein. In the case of alginate fibres, a weight ratio of liquor to textile material in the range from 100:1 to 500:1 may be found convenient. In the case of CMC fibres, a weig

REFERENCES:
patent: 4579943 (1986-04-01), Kamide et al.
patent: 5470576 (1995-11-01), Patel
S. Thomas et al, "Examining the Properties and Uses of Two Hydrogel Sheet Dressings", Journal of Wound Care, 2(3):176-179 (May, 1993).

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