Mineral substituted hydroxyapatite coatings deposited on nanoporous TiO₂ modulate the directional growth and activity of osteoblastic cells†

The biocompatibility of anodized titanium (TiO₂) was improved by electrophoretically deposited mineral (strontium (Sr), magnesium (Mg) and zinc (Zn)) substituted hydroxyapatite (M-HAP). The M-HAP layer was grown on the anodized Ti surface at different deposition temperatures (room temperature, 60 and 80 C). The phases and morphologies of the M-HAP layers were influenced by the deposition temperature. The coatings were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy equipped with energy dispersive X-ray analysis (SEM-EDX). Also, the effects of temperature and the mineral substitution of Sr, Mg and Zn for Ca on the physiochemical and biological properties of the M-HAP coatings were evaluated by the mechanical strength, ion dissolution and proliferation, alkaline phosphatase (ALP) activity and osteogenic expression of osteoblast like cells MG66 (HOS). Thus, the M-HAP deposition of TiO₂ will serve as a potential candidate for orthopedic applications.