Enhancing the antibacterial activity of near-infrared light-triggered photothermal therapy using hybrid Au/ZnSe nanodumbbells

Photothermal therapy (PTT) for bacterial infection is an effective alternative to antibiotics. However, the excitation light with short wavelength which has unsatisfactory tissue penetration and the poor photothermal (PT) effect hinder its development. A PT agent which can achieve second near-infrared (NIR-II) light induced enhanced antibacterial PTT is essential. Here, we designed and synthesized hybrid plasmonic Au/ZnSe nanodumbbell heterostructures (AZN), and applied the heterostructures to treat bacterial infection by effective PTT under NIR-II light irradiation. In the AZN heterostructures, Au nanorods (NRs) are tailored to extend the excitation light to the NIR-II regions, which provides the possibility for NIR-II light triggered PTT. The two ZnSe semiconductor caps which have a higher conduction band (CB) block hot electron injection from Au NRs. Moreover, the two ZnSe semiconductor caps, as the passivation layers, can prevent the contact of hot electrons with the surrounding medium, resulting in a higher PT conversion efficiency. Consequently, AZN produced more heat than Au NRs under the same laser irradiation. AZN exhibited outstanding antibacterial ability for both Gram-positive and Gram-negative bacteria in vitro. In vivo antibacterial tests further proved that AZN, as an excellent photothermal agent, exhibited better antibacterial ability than Au NRs.