1 Influence of bacteria on silver dissolution from silver-palladium surfaces

Silver-palladium surfaces are potentially used for bacterial and biofilm inhibition by generating micro-electric fields and electrochemical redox processes, and it is desired that the release of any metal ion will be at low concentration. However, in some specific environments, undesired silver dissolution can occur which can be recognized as a result of corrosion or deterioration of the silver-palladium surface, and will reduce the lifetime of the surface and contaminate the surroundings. The effect of bacteria, biofilm and solution contents on silver stability is therefore of interest, if silver-palladium surfaces are used in biologically active systems. In this study, a series of 24- and 72-hour immersion tests using several solutions was performed for the evaluation of silver dissolution and study of the mechanism. The quantitative data on silver dissolution and the correlation between silver dissolution, solution contents, and surface-associated bacteria were obtained. It was not surprising that chemicals aggressive to silver and silver compounds accelerated silver dissolution due to the formations of silver ions and silver complex ions, but a phenomenon of increased silver dissolution was found associated directly with the presence of bacteria. Experiments showed that surface-associated bacteria greatly increased silver dissolution from the silver-palladium surfaces due to the interactions between cell components and the surfaces, and the amount of surface-associated bacteria enhanced this effect