Silver containing wound dressing
A wound dressing having anti-microbial activity comprises a first fiber capable of bonding with silver (1) cations. The wound dressing comprises a blend of the first fiber to which silver (1) cations are bonded and a second fiber which is substantially free from silver. The wound dressing comprises from 0.01 to 5.0 percent by weight of silver (1) cations, based on the weight of fiber.
1. A wound dressing comprising gel-forming fibres having anti-microbial activity, comprising a first fibre, which is gel-forming and substantially insoluble in water having silver (I) cations bonded thereto and discoloring on exposure to light, and a second fibre, which is gel-forming and substantially free from silver, wherein the wound dressing comprises a uniform blend of the first fibre and the second fibre, said wound dressing comprising from 0.01 to 5.0 percent by weight of silver (I) cations based on a total weight of first and second fibres, whereby discoloration of the blend on exposure to light is lessened compared with discoloration on exposure to light of a batch of the first fibre having a same average amount of the silver (I) cations present as is present in the blend.
2. A wound dressing according to claim 1 , which comprises from 0.01 to 4.0 percent by weight of silver (I) cations based on the total weight of first and second fibres.
3. A wound dressing according to claim 1 , which comprises from 0.25 to 3.0 percent by weight of silver (I) cations based on the total weight of the first and second fibres.
4. A wound dressing according to claim 1 , wherein the first fibre is selected from a group consisting of a carboxymethylcellulose fibre, an alginate fibre, a chitosan fibre, a chitosan derivative fibre and an acrylic fibre.
5. A wound dressing according to claim 4 , wherein the first fibre is the carboxymethylcellulose fibre and the wound dressing contains from 1.0 to 2.0 percent by weight of silver (I) cations, based on the total weight of the first and second fibres.
6. A wound dressing according to claim 4 , wherein the first fibre is the alginate fibre and the wound dressing contains from 0.25 to 0.75 percent by weight of silver (I) cations, based on the total weight of the first and second fibres.
7. A wound dressing according to claim 4 , wherein the first fibre is the acrylic fibre which incorporates a comonomer to provide dye-sites in the first fibre.
8. A wound dressing according to claim 1 , wherein the second fibre contains no silver or low levels of silver such that it discolors to a degree which is not aesthetically objectionable.
9. A wound dressing according to claim 1 , wherein the second fibre contains no silver or low levels of silver such that it does not discolor at all.
10. A wound dressing according to claim 1 , wherein a ratio of the first fibre to the second fibre is in a range of from 5 to 20% by weight of the total weight of the first and second fibres.
11. A wound dressing according to claim 1 , wherein a ratio of the first fibre to the second fibre is in a range of from 0.5 to 25% by weight of the total weight of the first and second fibres.
12. A wound dressing according to claim 1 , wherein the first fibre includes at least 8% by weight, based on the total weight of the first and second fibres, of silver (I) cations.
13. A wound dressing according to claim 12 , wherein the first fibre is prepared using at least a 4% silver nitrate solution.
14. A wound dressing according to claim 1 , wherein the silver (I) cations are chemically bonded to the first fibre.
15. A wound dressing according to claim 1 , wherein the silver (I) cations are introduced into the first fibre by ion-exchange.
16. A wound dressing according to claim 1 , wherein the first fibre having silver (I) cations bonded thereto is pre-exposed to light prior to blending with the second fibre.
17. A wound dressing according to claim 1 , wherein the first fibre is a carboxymethylcellulose fibre and a degree of substitution of the carboxymethylcellulose fibre is less than 0.4.
18. A wound dressing according to claim 1 , wherein the second fibre is a carboxymethylcellulose fibre.
19. A wound dressing comprising gel-forming fibres having anti-microbial activity, comprising a first fibre, which is gel-forming and substantially insoluble in water having silver (I) cations bonded thereto and discoloring on exposure to light, and a second fibre, which is gel-forming and substantially free from silver, wherein the wound dressing consisting essentially of a uniform blend of the first fibre and the second fibre, said wound dressing comprising from 0.01 to 5.0 percent by weight of silver (I) cations based on a total weight of first and second fibres, whereby discoloration of the uniform blend on exposure to light is lessened compared with discoloration on exposure to light of a batch of the first fibre having a same average amount of the silver (I) cations present as is present in the uniform blend.