A review of TiO₂ NTs on Ti metal: Electrochemical synthesis, functionalization and potential use as bone implants

Degenerative diseases of bone such as osteoarthritis and osteoporosis can lead to bone fractures and immobility, compromising quality of life. Titanium (Ti)-based implants have been intensively investigated for bone repair, with these implants, demonstrating improved outcomes compared to stainless steel and cobalt-chrome alloys, owing to superior mechanical properties and biocompatibility. However, osseointegration between the Ti-based implants and the surrounding bone tissue needs to be improved. Surface modification of Ti-based implants provides a solution for addressing this, with electrochemical anodization becoming a realistic approach for the fabrication of hierarchical structured for example nanotubes (NTs), implant surfaces. Using this technique, biocompatibility and osteogenesis of the implant may be improved, by providing an appropriate site for bone cell attachment. In this review, we discuss the anodization of Ti-based implants as an approach for creating titanium dioxide nanotubes (TiO₂ NTs) on the implant surface. We further discuss the various ways of functionalizing the NT surface, to reduce post-operative infection and improve implant biocompatibility and osseointegration.