Antibacterial wound dressing

Abstract

An antibacterial wound dressing is based on or derived from gel-forming fibres such as carboxymethyl cellulose or alginate fibres having silver ions linked thereto at some but not all of the exchangeable sites such that the distribution of silver ions over the exchangeable sites is substantially uniform. The silvered fibres for the wound dressing can be prepared by contacting an assembly of precursor gel-forming fibres having exchangeable sites under conditions which do not cause irreversible gelling of the fibres with an amount of a solution containing silver ions so as to link silver ions at some but not all of the exchangeable sites, the whole of the assembly of precursor gel-forming fibres being contacted essentially simultaneously with the entire solution containing silver ions.

In the claims: 
     
         1 . An antibacterial wound dressing derived from gel-forming fibres having silver ions linked to not more than about 20% of the exchangeable sites on the gel-forming fibres, wherein the distribution of silver ions over the exchangeable sites is essentially uniform as shown by the uniform coloration of the dressing. 
     
     
         2 . An antibacterial wound dressing according to  claim 1 , wherein the silver ions are linked to not more than 10% of the exchangeable sites on the gel-forming fibres. 
     
     
         3 . An antibacterial wound dressing according to  claim 1 , wherein the gel forming fibres comprises lyocell-derived fibres. 
     
     
         4 . An antibacterial wound dressing according to  claim 1 , wherein the gel-forming fibres comprises carboxymethylated cellulose fibres. 
     
     
         5 . An antibacterial wound dressing according to  claim 1 , wherein the gel-forming fibres comprises calcium alginate or sodium/calcium alginate fibres 
     
     
         6 . An antibacterial wound dressing according to  claim 1 , wherein the silver content of the silvered fibres is from 0.01 to 10% by weight. 
     
     
         7 . An antibacterial wound dressing according to  claim 1 , wherein the silver content of the silvered fibres is from 0.1 to 5% by weight. 
     
     
         8 . An antibacterial wound dressing according to  claim 1 , wherein the silver content of the silvered fibres is from 0.5 to 2% by weight. 
     
     
         9 . An antibacterial wound dressing according to  claim 1 , wherein the silver content of the silvered fibres is from 0.9 to 1.5% by weight. 
     
     
         10 . An antibacterial wound dressing according to  claim 1 , wherein the antibacterial wound dressing is photostable. 
     
     
         11 . An antibacterial wound dressing of  claim 10 , wherein the wound dressing is treated with a metal halide. 
     
     
         12 . An antibacterial wound dressing of  claim 11 , wherein the metal halide is sodium chloride. 
     
     
         13 . A process for producing silvered fibres for use in antibacterial wound dressings including the steps of
 (i) forming an assembly of precursor gel-forming fibres having thereon exchangeable sites capable of exchange with silver ions to link silver ions to the fibre, and   (ii) essentially simultaneously contacting the assembly of precursor gel-forming fibres with a solution containing silver ions under conditions which do not cause irreversible gelling of the fibres, thereby to link silver ions at exchangeable sites, in which process the whole of the assembly of precursor gel-forming fibres is contacted essentially simultaneously with the entire solution containing silver ions, rather than being contacted gradually or partially, the solution containing silver ions being used in an amount such that enough silver ions are present to link with not more than about 20% of the exchangeable sites on the precursor gel-forming fibres, wherein the distribution of silver ions over the exchangeable sites is essentially uniform as shown by the essentially uniform coloration of the dressing.   
     
     
         14 . A process according to  claim 13 , wherein the silver ions are not linked with not more than about 10% of the exchangeable sites on the gel-forming fibres. 
     
     
         15 . A process according to  claim 13 , wherein the precursor gel-forming fibres comprises lyocell-derived fibres. 
     
     
         16 . A process according to  claim 13 , wherein the precursor gel-forming fibres comprises carboxymethylated cellulose fibres. 
     
     
         17 . A process according to  claim 13 , wherein the precursor gel-forming fibres comprises calcium alginate or sodium-calcium alginate fibres. 
     
     
         18 . A process according to  claim 13 , wherein the assembly of silvered, gel-forming fibres is further processed to form wound dressings. 
     
     
         18 . A process according to  claim 1 , wherein the wound dressings are photostable. 
     
     
         19 . A process according to  claim 18 , wherein the wound dressings are treated with a metal halide. 
     
     
         20 . A process according to  claim 18 , wherein the metal halide is sodium chloride. 
     
     
         21 . A process according to  claim 13 , wherein the silver content of the silvered fibres is from 0.01 to 10% by weight. 
     
     
         22 . A process according to  claim 13 , wherein the silver content of the silvered fibres is from 0.1 to 5% by weight. 
     
     
         23 . A process according to  claim 13 , wherein the silver content of the silvered fibres is from 0.5 to 2% by weight. 
     
     
         24 . A process according to  claim 13 , wherein the silver content of the silvered fibres is from 0.9 to 1.5% by weight. 
     
     
         25 . A process according to  claim 13 , wherein the silver content of the solution is between 0.1 to 1.0% w/v. 
     
     
         26 . A process according to  claim 13 , wherein the silver content of the solution is between 0.25 to 0.5% w/v. 
     
     
         27 . A process according to  claim 13 , wherein the silver content of the solution is 0.35% w/v. 
     
     
         28 . A process according to  claim 13 , in which the process is a batch process wherein the assembly of precursor gel-forming fibres is contacted with the solution containing silver ions by dipping it rapidly and entirely into the solution. 
     
     
         29 . A process according to  claim 28 , wherein the solution is held in a container and is an amount required completely to cover the precursor gel-forming fibres so that the fibres fill the solution within the container. 
     
     
         30 . A process according to  claim 28 , wherein the time interval between the beginning of the dipping of the assembly of precursor gel-forming fibres to form the wound dressing into the solution and the moment at which the assembly of precursor gel-forming fibres to form the wound dressing is entirely dipped into the solution is not more than about 10 seconds. 
     
     
         31 . A process according to  claim 30 , wherein said time interval is not more than 5 seconds. 
     
     
         32 . A process according to  claim 28 , wherein the assembly of precursor gel-forming fibres to be dipped is dry. 
     
     
         33 . A process according to  claim 29 , wherein the solution containing silver ions is held in a closed container. 
     
     
         34 . A process according to  claim 29 , wherein the solution containing silver ions is held in an open container.