Osteogenic and long-term antibacterial properties of Sr/Ag-containing TiO2 microporous coating in vitro and in vivo.

Bacterial infection and poor osseointegration are two critical issues that need to be solved for long-term use of titanium implants. As such, Sr/Ag-containing TiO2 microporous coatings were prepared on a Ti alloy surface in the current study via a single-step microarc oxidation technique. The coatings showed both good cytocompatibility in vitro and biosafety in vivo. Sr/Ag incorporation brought no significant change in the surface micromorphology and physicochemical properties, but endowed the coating with strong osteogenic activity and long-term antibacterial capability in vitro. Furthermore, the osteogenic and antibacterial capability of the coating was also confirmed in vivo. In a rat osseointegration model, new bone formation, implant-bone contact, removal torque and bone mineralization were all significantly increased in the M-Sr/Ag group when compared with those in group M, although they were slightly lower than those in group M-Sr. In a periimplantitis model, no rats suffered infection in the M-Sr/Ag group after 3 months of osseointegration and 5 weeks of bacterial inoculation period, when compared to 100% and 75% infection rates in M and M-Sr groups, respectively. In addition, active bone remodeling and many mesenchymal cells were observed in the M-Sr group, suggesting good bone regeneration potential in Sr-containing coatings in the case of controlled periimplantitis. Overall, the Sr/Ag-containing TiO2 microporous coating is valuable for preventing periimplantitis and improving implant reosseointegration, and is therefore promising for long-term and high quality use of titanium implants.

The effect of strontium content on physicochemical and osteogenic property of Sr/Ag-containing TiO2 microporous coatings.

Strontium (Sr) is the most common element introduced into TiO2 coatings to strengthen the osteogenic property of titanium implants. However, the optimal Sr content and its effect on osteogenic and physicochemical properties of the coatings need to be clarified. In the current study, TiO2 microporous coatings with different contents of Sr (9.64-21.25 wt %) and silver (Ag) (0.38-0.75 wt %) were prepared via micro-arc oxidation technique. Sr contents did not change physicochemical properties of the coatings, including surface microstructure, micropore size and distribution, phase composition, roughness and hydrophilicity. Meanwhile, higher Sr contents (18.23-21.25 wt %) improved cytocompatibility, proliferation and alkaline phosphatase (ALP) activity of preosteoblasts, even the coatings underwent 30 days' PBS immersion. Furthermore, higher Sr contents facilitated preosteoblast growth and spreading, which are essential for their proliferation and osteogenic differentiation. Therefore, it is promising to incorporate higher Sr content (18.23-21.25 wt %) within TiO2 microporous coatings to improve their osteogenic capability.