Calcium phosphate coating containing silver shows high antibacterial activity and low cytotoxicity and inhibits bacterial adhesion

Surgical site infection is one of the serious complications of orthopedic implants. In order to reduce the incidence of implant-associated infections, we developed a novel coating technology of calcium phosphate (CP) containing silver (Ag), designated Ag-CP coating, using a thermal spraying technique. In this study, we evaluated the antibacterial efficacy and biological safety of this coating. In vitro antibacterial activity tests showed that the growths of Escherichia coli, Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) are completely suppressed on Ag-CP coating. In vitro bacterial adherence tests revealed that the number of adherent bacteria on the surface of this coating is significantly less (p < 0.02) than that on the surface of the CP coating. Moreover, the Ag-CP coating completely inhibits MRSA adhesion [<10 colony-forming units (CFU)] when 102 CFU MRSA is inoculated. On the other hand, V79 Chinese hamster lung cells were found to grow on the Ag-CP coating as well as on the CP coating in a cytotoxicity test. These results indicate that the Ag-CP coating on the surface of orthopedic implants exhibits antibacterial activity and inhibits bacterial adhesion without cytotoxicity.