Promoting osseointegration of titanium implants through magnesium- and strontium-doped hierarchically structured coating

This study aimed to investigate the effect of magnesium (Mg) and strontium (Sr) surface modification on osseointegration of titanium (Ti) implants with a hierarchically structured coating. Mg- and Sr-doped hierarchical surface coating has been fabricated on Ti implant through the hydrothermal method. Scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectrometer (EDS), inductively coupled plasma/optical emission spectroscopy (ICP-OES) and contact-angle measurement have been applied to characterize the surface coating. The biocompatibility and osseointegration of Ti implants with Mg- and Sr-dropped hierarchical coating have been assessed in vivo using a rat tibia implantation model. The proposed mechanism that improves osteointegration of Mg- and Sr-doped coating Ti implant has been evaluated by culturing rat bone marrow stromal cells (BMSCs) alone or co-culturing Schwann cells (SCs) and BMSCs on the coating surfaces. Our results proved that both Mg- and Sr-doped hierarchical coating could promote osseointegration with Mg exerted a stronger effect in vivo. The in vitro outcomes showed that Mg-doped coating enhances BMSCs adhesion, while the Sr-doped surface promotes osteogenic differentiation of BMSCs. Furthermore, when BMSCs were cultured with SCs, Mg-dropped surfaces accelerated not only the adhesion but also osteogenic differentiation of BMSCs. Conclusively, the hierarchical surface coating with trace element modification can provide a strong guarantee for endosseous applications of titanium (Ti) implants, and Mg-doped hierarchical coating is more effective in promoting osseointegration than Sr modification.