A biocompatible sol–gel derived titania coating for medical implants with antibacterial modification by copper integration

Hans Gollwitzer, Maximilian Haenle, Wolfram Mittelmeier, Frank Heidenau, Norbert Harrasser

Implant-associated infections are dangerous complications and may cause dramatic illness with hematogeneous spread of bacteria and secondary infections. Since treatment of these infections remains most challenging and commonly requires implant removal, prevention is of utmost importance. In the present work a titania-sol was equipped with a copper salt resulting after calcination in a titania coating (TiO2) with antibacterial properties combined with good cytocompatibility. In vitro tests with bacteria as well as tissue cells were carried out under corresponding conditions. Mouse fibroblasts and different staphylococcal strains were used for growth inhibition assays with serial dilutions of CuCl2. Cultivation on the surface of bare Ti6Al4V, TiO2-coated and copper-filled TiO2-coated Ti6Al4V samples was performed with both bacteria and tissue cells. Bacterial and cellular proliferation and mitochondrial activity were hereby determined. Coating of Ti6Al4V with pure TiO2significantly improved cytocompatibility compared to the uncoated alloy. In the growth inhibition assays, fibroblasts tolerated higher concentrations of copper ions than did bacteria. Nevertheless, copper integration reduced fibroblast proliferation and mitochondrial activity on the surface coating. On the other hand, integration of copper into the TiO2-coating significantly reduced adhesion of viable bacteria resulting in a promising combination of cytocompatibility and antibacterial properties. Additionally, significant bacterial growth inhibition by antibacterial amounts of copper was also demonstrated in the supernatant. In conclusion, the copper-loaded TiO2-coatings for medical implants may be a promising approach to reduce the rate of implant-associated infections.