In vitro cytocompatibility and corrosion resistance of zinc-doped hydroxyapatite coatings on a titanium substrate

To improve biocompatibility and corrosion resistance during the initial implantation stage, zinc-substituted hydroxyapatite (ZnHAp) coating was fabricated on pure titanium by the electrolytic deposition method. The morphology, microstructure and chemical composition of the coating were investigated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis and Fourier transform infrared spectroscopy. The prepared ZnHAp crystals were calcium deficient and were carbonated owing to the incorporation of some Zn2+. This incorporation of Zn2+ into the HAp significantly reduced porosity and caused the coating to become noticeably denser. In addition, the Zn2+ ions were homogeneously distributed in the coating. The potentiodynamic polarisation test revealed that the ZnHAp-coated surface showed superior corrosion resistance over that of the HAp-coated surface and bare Ti. The in vitro bioactivity was evaluated in a simulated body fluid, which revealed that the ZnHAp coating can rapidly induce bone-like apatite formation of nuclear and growth features. In addition, the cell response tests showed that the MC3T3-E1 cells on the ZnHAp coating clearly enhanced the in vitro cytocompatibility of Ti compared with the same cells on HAp coating. ZnHAp coating was thus beneficial for improving biocompatibility.