Copper as an alternative antimicrobial coating for implants-An in vitro study

AIM To investigate osteoconductive and antimicrobial properties of a titanium-copper-nitride(TiC uN) film and an additional BONIT~? coating on titanium substrates.METHODS For micro-structuring, the surface of titanium test samples was modified by titanium plasma spray(TPS). On the TPS-coated samples, the Ti Cu N layer was deposited by physical vapor deposition. The BONIT~? layer was coated electrochemically. The concentration of copper ions released from TiC uN films was measured by atomic absorption spectrometry. MG-63 osteoblasts on Ti Cu N and BONIT~? were analyzed for cell adhesion, viability and spreading. In parallel, Staphylococcus epidermidis(S. epidermidis) were cultivated on the samples and planktonic and biofilm-bound bacteria were quantified bycounting of the colony-forming units. RESULTS Field emission scanning electron microscopy(FESEM) revealed rough surfaces for TPS and TiC uN and a special crystalline surface structure on TiC uN + BONIT~?. TiC uN released high amounts of copper quickly within 24 h. These release dynamics were accompanied by complete growth inhibition of bacteria and after 2 d, no planktonic or adherent S. epidermidis were found on these samples. On the other hand viability of MG-63 cells was impaired during direct cultivation on the samples within 24 h. However, high cell colonization could be found after a 24 h pre-incubation step in cell culture medium simulating the in vivo dynamics closer. On pre-incubated TiC uN, the osteoblasts span the ridges and demonstrate a flattened, well-spread phenotype. The additional BONIT~?-coating reduced the copper release of the TiC uN layer significantly and showed a positive effect on the initial cell adhesion.CONCLUSION The Ti Cu N-coating inhibits the formation of bacterial biofilms on orthopedic implants by influencing the "race for the surface" to the advantage of osteoblasts.