ON or OFF: Triggered therapies from anodized nano-engineered titanium implants.

Surface modification of Ti implants has been advocated as a means to augment osseointegration and enable antibacterial functions. Among the various modification strategies, the fabrication of TiO2 nanotubes (TNTs) on Ti implants via electrochemical anodization has shown promising outcomes. However, such systems do not enable activation, deactivation and tuning of the therapies after the implant placement, in response to local bone microenvironment conditions, to achieve a maximal therapeutic effect. Therapies administered from the implant surface in situ and managed by internal/external triggers can shift the paradigm in providing responsive therapy. In this review, we explore the various triggers that have been employed to achieve triggered therapies from the surface of modified Ti implants, with special focus on TNTs. We critically evaluate the current research advances in this domain (including biological, electrical, magnetic and electromagnetic triggers), cytotoxicity concerns and research challenges that must be addressed to achieve clinical translation of triggered therapies from modified Ti implants.