Hierarchically hybrid biocoatings on Ti implants for enhanced antibacterial activity and osteogenesis

Titanium (Ti) is widely applied as bone-anchoring implants in dental and orthopedic applications owing to its superior mechanical characteristics, high corrosion resistance, and excellent biocompatibility. Nevertheless, Ti-based implants with the deficiencies of insufficient osteoinduction and associated infections can result in implant failure, which significantly limits its applications in some cases. In this work, hierarchically hybrid biocoatings on Ti implants are developed by gradual incorporation of polydopamine (PDA), ZnO nanoparticles (nZnO), and chitosan (CS)/nanocrystal hydroxyapatite (nHA) via oxidative self-polymerization, nanoparticle deposition, solvent casting and evaporation methods for enhancing their antibacterial activity and osteogenesis. The modification of PDA on porous reticular Ti substrates greatly reduces the surface roughness, wettability, protein adsorption, and provides high adhesion to the deposited nZnO. Further, incorporating nZnO on PDA-coated Ti surfaces affects the surface structure and wettability, significantly inhibits the growth of both Staphylococcus aureus and Escherichia coli. Moreover, the CS/nHA-doped coating on the nZnO-modified Ti surfaces remarkably improves cytocompatibility and enhances the osteogenic differentiation of MC3T3-E1 cells by upregulating the protein expression of alkaline phosphatase. This work offers a promising alternative for developing Ti implants with long-lifetime bioactivity to achieve strong antibacterial ability and enhanced bone formation for potential dental/orthopedic applications.