Incorporation of Sr2+ and Ag nanoparticles into TiO2 nanotubes to synergistically enhance osteogenic and antibacterial activities for bone repair

Osteogenic and antibacterial activities are two basic requirements for orthopedic implants. The present study mainly focused on the investigation of the osteoblast behaviors and antibacterial activities of Sr/Ag-incorporated titanium dioxide (TiO2) nanotube array (TNT) on the titanium surface. To this end, the Sr-incorporated TNT was firstly fabricated on the titanium surface by electrochemical anodization and hydrothermal treatment, and then Ag nanoparticles (AgNPs) were incorporated onto the nanotubes by reduction of the adsorbed Ag+ through ultraviolet (UV) irradiation. The TiO2 nanotubes had excellent hydrophilicity and Sr incorporation can further enhance the hydrophilicity; however, the AgNPs loading could slightly increase water contact angle. The release of Sr2+ can not only promote osteoblast adhesion, proliferation and mineralization, but also up-regulate the alkaline phosphatase (ALP) and osteocalcin (OCN) expression. The introduction of AgNPs on Sr-incorporated nanotubes did not significantly influence the osteoblast cell behaviors; however, it can effectively inhibit the adhesion and growth of Escherichia coli. Therefore, the method of the present study is expected to be suitable for surface modification of titanium surface to simultaneously enhance the osteo-bonding ability and antibacterial activities for bone repair.