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

Abstract

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.