Antibacterial activity of an NIR-induced Zn ion release film

Photothermal therapy originated from using gold nanorods (GNRs) and near-infrared (NIR) irradiation has been widely used in the antibacterial field. Zn element exhibits antimicrobial activity against various bacterial and fungal strains. In this study, a bilayer film, consisting of GNRs as the inner layer and a polydopamine layer containing Zn element (PDA@Zn) as the outer layer, was deposited on the Ti surface. The results testified that all the GNR-modified surfaces had the same photothermal conversion efficiency. The Ti surface modified with GNR and PDA@Zn layers had better antibacterial activity against E. coli and S. aureus due to the GNR-induced photothermal effect and the antibacterial Zn element. Moreover, the accelerated release of Zn ions from the PDA@Zn layer was attributed to the GNR-induced high temperature under the NIR irradiation, which caused the concentration of Zn ions to be high enough to kill the surrounding bacteria. This study illustrates that a composite surface possessing both the contact and heat-responsive antibacterial property was constructed on titanium for potential clinical applications.