Balancing the Antibacterial and Pro-osteogenic Properties of Ti-Based Implants by Optimizing the Fluorination/Oxidation Level of Nanostructured Fluoride-Doped Hybrid Tantalum Oxide

The two main problems with titanium implants are bacterial infection and insufficient osseointegration. The balance between osteoinductivity and antibacterial activity remains a formidable challenge because toxicity is usually introduced with enhancement of the antibacterial ability. In this research, a nanostructured fluoride-doped hybrid tantalum oxide (TaFO) was prepared on titanium by plasma-based surface modification. By a change of the fluorine-oxygen ratio, the fluorination/oxidation (F/O) level was optimized, and the dual effects of antibacterial activity and osteogenic promotion were achieved. The TaFO samples exhibited remarkable antibacterial abilities when the surface F/O proportion level exceeded 0.11. The antibacterial effect of the sample may be caused by the combined action of multiple factors: the superhydrophilic coating inhibits bacterial adhesion, the metal oxide induces oxidative stress, and the F^--induced acidified microenvironment inactivates adenosine triphosphate (ATP) synthesis and induces bacterial oxidative stress. In addition, with a proper F/O level, the TaFO-II sample not only significantly promoted the proliferation and differentiation of osteoblasts, enhanced alkaline phosphatase (ALP) activity and extracellular matrix mineralization, and increased the expression levels of important osteogenic genes <i>in vitro</i> but also effectively resisted bacterial infection, accelerated bone regeneration, and promoted osseointegration. In conclusion, this study introduces an approach to successfully imparting selective antibacterial and osteogenic properties to titanium implants, which has a large potential to simultaneously address the issues of bone regeneration and infection in clinical applications.