Yajing Yan

Osteoblastic cell responses and antibacterial efficacy of Cu/Zn co-substituted hydroxyapatite coatings on pure titanium using electrodeposition method

Effective physiological bone integration and absence of bacterial infection are essential for a successful orthopaedic or dental implant. This work elucidated the antibacterial efficacy and cytocompatibility of an electroplated Cu(II) and Zn(II) co-substituted hydroxyapatite (HAP) (i.e., ZnCuHAP) coating on commercially pure titanium (Ti-cp). To improve the antibacterial property of pure HAP, Cu2+ was substituted into its structure. Simultaneously, Zn2+ is co-substituted as a secondary material into CuHAP to offset the potential cytotoxicity of Cu, because an elevated Cu concentration is toxic. The as-deposited coatings were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Co-doping of Zn2+ and Cu2+ into HAP reduced the porosity, resulting in a denser coating. The Zn2+ and Cu2+ ions were homogenously co-deposited into HAP films. Potentiodynamic polarisation test revealed that the ZnCuHAP covered coating provided good barrier characteristics and achieved superior corrosion protection for Ti substrates. The as-prepared ZnCuHAP coating was found to be highly effective against Escherichia coli in vitro. In vitro biocompatibility tests and MTT were employed to assess the cytotoxicity of ZnCuHAP coating with osteoblast-like MC3T3-E1 cells. No adverse effect or cytotoxicity on osteoblasts by Zn/Cu addition was observed, revealing that the co-substitution of Zn in CuHAP efficiently offsets the adverse effects of Cu and improves the performance compared with that of pure HAP.

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.