Plasmon-Accelerated Generation of Singlet Oxygen on an Au/MoS2 Nanohybrid for Enhanced Photodynamic Killing of Bacterial Pathogens/Cancerous Cells

Benefiting from its strong cytotoxic features, singlet oxygen (O-1(2)) has garnered considerable research attention in photodynamic therapy (PDT) and thus, plenty of inorganic PDT agents have been recently developed. However, inorganic PDT agents consisting of metal/semiconductor hybrids are surprisingly rare, bearing very low O-1(2) quantum yield, and their in vivo PDT applications remain elusive. Herein, we provide an unprecedented report that the Au/MoS2 hybrid under plasmon resonant excitation can sensitize O-1(2) generation with a quantum yield of about 0.22, which is much higher than that of the reported hybrid-based photosensitizers (PSs). This significant enhancement in O-1(2) quantum yield is attributed to the hot-electron injection from plasmonic AuNPs to MoS2 NSs due to the matched energy levels. Electron paramagnetic resonance (EPR) spectroscopy with spin trapping and spin labeling verifies the plasmonic generation of hot charge carriers and reactive oxygen species such as superoxide and O-1(2). This plasmonic PDT agent shows a remarkable photodynamic bacterial inactivation in vitro and anti-cancer therapeutic ability both in vitro and in vivo, which is solely attributed to high O-1(2) generation rather than the plasmonic photothermal effect. Hence, plasmonic Au/MoS2 with enhanced O-1(2) quantum yield and appreciable in vivo cancer plasmonic PDT performance holds great promise as an inorganic PS to treat near-surface tumors. As a first demonstration of how metal localized surface plasmon resonance could enhance O-1(2) generation, the present study opens up promising opportunities for enhancing O-1(2) quantum yield of hybrid-based PSs, leading to achieving a high therapeutic index in plasmon PDT.