Synergistic antibacterial activity of physical-chemical multi-mechanism by TiO2 nanorod arrays for safe biofilm eradication on implant

Treatment of implant-associated infection is becoming more challenging, especially when bacterial biofilms form on the surface of the implants. Developing multi-mechanism antibacterial methods to combat bacterial biofilm infections by the synergistic effects are superior to those based on single modality due to avoiding the adverse effects arising from the latter. In this work, TiO₂ nanorod arrays in combination with irradiation with 808 near-infrared (NIR) light are proven to eradicate single specie biofilms by combining photothermal therapy, photodynamic therapy, and physical killing of bacteria. The TiO₂ nanorod arrays possess efficient photothermal conversion ability and produce a small amount of reactive oxygen species (ROS). Physiologically, the combined actions of hyperthermia, ROS, and puncturing by nanorods give rise to excellent antibacterial properties on titanium requiring irradiation for only 15 min as demonstrated by our experiments conducted <i>in vitro</i> and <i>in vivo</i>. More importantly, bone biofilm infection is successfully treated efficiently by the synergistic antibacterial effects and at the same time, the TiO₂ nanorod arrays improve the new bone formation around implants. In this protocol, besides the biocompatible TiO₂ nanorod arrays, an extra photosensitizer is not needed and no other ions would be released. Our findings reveal a rapid bacteria-killing method based on the multiple synergetic antibacterial modalities with high biosafety that can be implemented <i>in vivo</i> and obviate the need for a second operation. The concept and antibacterial system described here have large clinical potential in orthopedic and dental applications.