Photostable Wound Dressing Materials and Methods of Production Thereof
The invention provides a method of preparing an antimicrobial sponge material for medicinal use, comprising the steps of: treating an anionic polysaccharide with a solution of a silver salt to produce a complex of the anionic polysaccharide with silver; dispersing said complex in aqueous ascorbic acid to form an acidified dispersion, followed by freeze-drying or solvent-drying the dispersion to form the sponge material. Also provided is a photostabilized antimicrobial sponge material comprising an anionic polysaccharide complexed with silver (I) ions, wherein the sponge further comprises ascorbic acid, and the sponge has a substantially white colour that is substantially stable against discoloration on exposure to light. Also provided are wound dressings comprising such materials, and the use of such materials in medicine.
1 . A method of preparing an antimicrobial sponge material for medicinal use, comprising the steps of:
treating an anionic polysaccharide with a solution of a silver salt to produce a complex of the anionic polysaccharide with silver;
dispersing said complex in aqueous ascorbic acid to form an acidified dispersion, followed by freeze-drying or solvent-drying the dispersion to form the sponge material.
2 . The method of claim 1 wherein the ionic polysaccharide consists essentially of oxidized regenerated cellulose (ORC).
3 . The method of claim 1 , wherein the said dispersion further comprises one or more additional medically acceptable polymeric materials dispersed therein.
4 . The method of claim 3 , wherein the dispersion further comprises a substantially silver-free ORC and a collagen, and the silver concentration in the dispersion is from about 0.1% to about 2% by weight based on total polymeric solids.
5 . The method of claim 1 wherein the dispersion has a pH of from about 3 to about 4, and a solids concentration of from about 0.5% to about 2%.
6 . A photostabilized antimicrobial sponge material obtained or obtainable by a method according to claim 1 .
7 . A photostabilized antimicrobial sponge material comprising an anionic polysaccharide complexed with silver (I) ions, wherein the sponge further comprises ascorbate, and the sponge has a substantially white colour that is substantially stable against visible discoloration on exposure to natural daylight for 24 hours at 25° C. and in air.
8 . A wound dressing comprising an antimicrobial sponge material according to claim 6 .
9 . A wound dressing according to claim 8 , wherein the wound dressing is sterile and packaged in a microorganism-impermeable container.
10 . Use of ascorbic acid in an antimicrobial material comprising a silver (I) salt of a medically acceptable polyanionic acid to stabilize said material against discoloration on exposure to light.