NIR Light-Driven Photocatalysis on Amphiphilic TiO2 Nanotubes for Controllable Drug Release.

Titanium dioxide (TiO2) nanomaterials have attracted much interest in life science and biological fields because of their excellent photocatalytic activity and good biocompatibility. However, owing to its wide band gap, photocatalysis of TiO2 can be only triggered by UV light. The limited transparent depth of UV light and the generated reactive oxygen species (ROSs) cause inflammation response of skin tissue, thus posing two major challenges in the photocatalytic application of TiO2-based materials in drug delivery and other biotechnology fields. Here, we propose an upconversion-related strategy to enable the photocatalytic activity of TiO2 nanotubes in near-infrared light and apply the system as a controllable drug delivery platform. More importantly, the ROS-induced cytotoxicity and the preleaching of payloads are significantly reduced on the as-proposed amphiphilic TiO2 nanotubes. The hydrophobic monolayers are served as a "cap" to provide protection for ROS-induced inflammation and long-term storability. This amphiphilic drug delivery system broadens the potential applications of TiO2-based nanomaterials in biomedicine.