Determination of silver release from wound care products

Silver is used as an antimicrobial agent in wound care products due to its effectiveness against a broad range of bacteria. Despite extensive use of silver-containing dressings, silver release measurements vary significantly for instance in release method and test fluid used, thus making it hard to compare results. In addition, existing methods for silver release involve the dressing being totally saturated with test fluid, this however does not mirror the real situation in wound treatment. The aim with this master thesis is to develop a test method for measuring silver release from silver-containing dressings that are not fully saturated with test fluid. Silver release at different degrees of moisture saturation was investigated using inductively coupled plasma optical emission spectroscopy. In order to simulate wound-like conditions pieces of dressings were pre-wetted with test fluid to a certain moisture level and placed on an acceptor compartment (AC) containing a defined amount of salts and proteins. After incubation, the AC was digested in acid prior to analysis with ICP-OES. Results show that silver release depends on the test fluid used. For deionized water a silver release of at most 19 μg Ag/cm2 AC was obtained. For solution A, which consists of distilled water with NaCl and CaCl2, a release of 1 μg Ag/cm2 AC was found. Silver release for SWF, which consists of fetal calf serum mixed with equal amount of peptone water, was 4 μg Ag/cm2 AC. Measurements performed on 0%, 25%, 50%, 75% and 100% moisture saturation show that silver release is dependent on the moisture saturation of dressing. A higher silver release was seen for dressings pre-wetted to higher moisture saturations. Digestion of the acceptor compartment prior to analysis with ICP-OES was found to be satisfactory. Finally, silver release on human skin was performed in order to evaluate the relevance of the method being developed. Results show good agreement between silver release in the acceptor compartment model used and skin as acceptor compartment which strengthens the relevance of the developed method.