Vacuum plasma sprayed coatings using ionic silver doped hydroxyapatite powder to prevent bacterial infection of bone implants.

Fast and efficient osseointegration of implants into bone is of crucial importance for their clinical success; a process that can be enhanced by coating the implant surface with hydroxyapatite (HA) using the vacuum plasma spray technology (VPS). However, bacterial infections, especially the biofilm formation on implant surfaces after a surgery, represent a serious complication. With ever-increasing numbers of antibiotic-resistant bacteria, there is great interest in silver (Ag) as an alternative to classical antibiotics due to its broad activity against Gram-positive and Gram-negative bacterial strains. In the present study, silver ions were introduced into HA spray powder by ion exchange and the HA-Ag powder was applied onto titanium samples by VPS. The Ag-containing surfaces were evaluated for the kinetics of the silver release, its antibacterial effect against Staphylococcus aureus as well as Escherichia coli, and possible cytotoxicity against human bone cells. The HA-Ag coatings with different concentrations of Ag displayed mechanical and compositional properties that fulfill the regulatory requirements. Evaluation of the Ag release kinetic showed a high release rate in the first 24 h followed by a decreasing release rate over the four subsequent days. The HA-Ag coatings showed no cytotoxicity to primary human bone cells while exhibiting antibacterial activity to E. coli and S. aureus.