Stable ZnO-doped hydroxyapatite nanocoating for anti-infection and osteogenic on titanium

Titanium and titanium alloys have been widely used in orthopedics and related fields. However, their clinical applications are limited due to the lack of anti-infection, osteoinductivity and angiogenic ability. In the present study, we utilized pulse electrochemical deposition method to prepare polypyrrole (PPy) by the in-situ oxidative polymerization of pyrrole (Py), and through the coordination and doping of ions, the function of PPy as a dual regulator of hydroxyapatite nanoparticles (HA-NPs) and zinc oxide nanoparticles (ZnO-NPs) was achieved. Bioactivity test showed that the composite coating could induce the formation of apatite, and the apatite was in a neat arrangement preferentially grew along the (002) crystal plane, indicating good bioactivity. The release test showed that the dual regulation effect of PPy coordination and doping reduced the release rate of Ca²⁺ and Zn²⁺ from the composite coating. Antibacterial tests showed that the composite coating against Escherichia coli and Staphylococcus aureus. Besides, bone marrow-derived mesenchymal stem cells (BMSCs) exhibited good adhesion, proliferation and differentiation on the composite coating, and fluorescence staining experiments demonstrated good osteoinductivity of the composite coating. In this study, a multifunctional composite coating with anti-infection, angiogenic and osteoinductivity was successfully constructed on the titanium surface via pulse electrochemical deposition method.