Ag nanoparticles incorporated tannic acid/nanoapatite composite coating on Ti implant surfaces for enhancement of antibacterial and antioxidant properties

Implant infections caused by bacteria and oxidative stress induced by reactive oxygen species (ROS) would seriously hinder the osseointegration at the interface of bone and titanium (Ti) implant, leading to a failure. Therefore, it is highly desirable to develop an implant surface modification with antibacterial and antioxidant functions. Silver (Ag), which exhibit a broad spectrum of antibacterial properties, was used in this work. Tannic acid (TA) was selected as the reducing agent to realize the generation of Ag nanoparticles , and as an antioxidant to achieve the antioxidative activity of Ti implants. So, a layer of anatase titanium dioxide (TiO 2 ) nanotubes with a diameter of 138.72 ± 14.02 nm was formed on the surface of Ti substrate by anodization and annealing, followed by loading Ag nanoparticles, growing bioactive hydroxyapatite (HA) crystals, and finally forming Ag-HA/TA composite coatings . Morphology and phase composition investigations detected the presence of Ag nanoparticles and HA crystals in the coatings. The results reveal the uniformly distributed Ag particles with a diameter of about 20– 80 nm and needle-like HA crystals with a diameter of about 18– 20 nm. Results of total antioxidant capacity tests indicate that the slow release of TA from the composite coatings leads to a persistent antioxidative activity. The antibacterial and cell compatibility tests in vitro reveal that the Ag-HA/TA coating has high antibacterial activity against both Escherichia coli and Staphylococcus aureus and good cytocompatibility effect with MC3T3-E1 cell lines. This study presents a simple and effective method for the incorporation of antibacterial agents and antioxidant into HA coatings to modify metallic implant surfaces.