Silver/copper-mixed layers as antimicrobial surface coating

The emergence of microbial organisms resistant to antibiotics leads to an increase of health care costs up to almost 2 billion dollar per year in America. Surface modification by metal deposition is one possibility to treat and prevent infections. The antimicrobial effect of silver is known for a long time. But current applications like coatings on patches are based on not defined metal concentrations and an unknown timescale of dissolution. This can cause serious problems like overreaction, cytotoxicity and other effects. Also copper shows antimicrobial behavior, but it features minor problems concerning cytotoxic effects. Complementing silver with copper can even increase the antimicrobial effectiveness due to synergistic effects. Polyurethane as a model substrate for medical devices was coated with Ag/Cu-mixed layers using PVD-technology. The coatings were analyzed by SEM/EDX. Their dissolution behavior in test liquids was investigated by ICP-MS. The antimicrobial efficacy was examined using specialized microbiological methods and the model organism Escherichia coli K12. In addition cell biological experiments were accomplished to determine biocompatibility. The results constitute a basis to apply silver and copper for antimicrobial coatings using physical vapor deposition as method of choice. The coatings can be adapted specifically for every customer and application.