EP(UK) 1343510 in the name of Convatec Technologies.
The patent was about antimicrobial wound dressings impregnated with silver.
The IPKat can do no better than copy the judgement for the background to the technology:
- Wound dressings have advanced over the years and in the 1990s wound dressings were developed which were intended to keep the wound surface moist. One method of achieving this aim was to use materials which formed a gel. One class of gelling wound dressing used alginate materials. Another kind used carboxymethyl cellulose (CMC).
- Infection is a problem associated with wounds and
consequently there is a need to both prevent and treat infection resulting from
wounds. Antimicrobial agents can be used topically to achieve this result. A dry
wound environment was not conducive to bacterial, fungal or viral growth.
However, as gel dressings became more popular the problem of bacterial growth
became more apparent. One antimicrobial agent known for many years is silver.
Silver has a number of advantages for topical application including low
toxicity. However there is a practical problem associated with the use of silver
in wound dressings. It is light stability. This sensitivity is well known. For
example the light sensitive nature of silver salts was used in photography for
- The patent relates to a method of preparing a light stabilized antimicrobial material for use in wound dressings and medical devices. Essentially the method is one whereby a wound dressing material can be made which comprises silver as an antimicrobial agent but which is stable in the presence of light.
1. A method of preparing a light stabilized antimicrobial material, characterised in that the method comprises the steps of:
(a) preparing a solution comprising an organic solvent and a source of silver in a quantity sufficient to provide a desired silver concentration in said material;
(b) subjecting a material which includes gel-forming fibres containing one or more hydrophilic, amphoteric or anionic polymers to said solution for a time sufficient to incorporate said desired silver concentration into said polymer, wherein said polymer comprises a polysaccharide or modified polysaccharide, a polyvinylpyrrolidone, a polyvinyl alcohol, a polyvinyl ether, a polyurethane, a polyacrylate, a polyacrylamide, collagen, or gelatin or mixtures thereof; and
(c) subjecting said polymer, during or after step (b) to one or more agents selected from the group consisting of ammonium salts, thiosulphates, chlorides and peroxides which facilitate the binding of said silver on said polymer, the agent being present in a concentration between 1% and 25% of the total volume of treatment, which material is substantially photostable upon drying, but which will dissociate to release said silver upon rehydration of said material.
|Is this how the dressing is used?|
Materials which are particularly adapted for the inventive method include gel-forming fibers such as Aquacel™
Smith & Nephew's best point is the argument that when the gel forming fibres idea is introduced at the top of p5 of the application the language would be understood as a disclosure not that any gel forming fibres would do and Aquacel was simply an example but that the gel forming fibres being discussed are those like Aquacel. [feline emphasis]