Microbial contamination and the prevalence of resistant bacteria is considered a worldwide public health problem. Therefore, recently, great efforts have been made to develop photoresponsive platforms for the simultaneous photodynamic antibacterial (PDA) and photothermal antibacterial (PTA) therapy processes as mediated by specific light. However, owing to the absorption mismatches of the photothermal agents and photodynamic photosensitizers, it has been discovered that many synergistic photoresponsive antibacterial platforms cannot be excited by a single-wavelength light. In this study, silver bismuth sulfide quantum dots (AgBiS2 QDs) identified from the literature as a near-infrared light (NIR) that triggers bifunctional materials with simultaneous photodynamic and photothermal effects for photoresponsive bacterial killing were used. Specifically, AgBiS2 QDs were successfully synthesized via a bottom-up approach, using polyethylenimine (PEI) as an assistant molecule. With PEI wrapping, the attachment between the negatively charged membrane surfaces of the bacterial cells and AgBiS2 QDs was enhanced via the electrostatic interactions. The photodriven antibacterial activity of AgBiS2 QDs was then investigated against both S. aureus and E. coli. The results revealed a significant reduction in bacterial survival. The killing effect was found to be independent of the AgBiS2 QDs, and redox potentials controlled the photogenerated electrons that thermodynamically favored the formation of multiple reactive oxygen species (ROS). A possible phototriggered antibacterial mechanism was then proposed in which the AgBiS2 QDs are anchored first to the bacterial surface and then induce breaking on its outer membrane by high local heat and ROS under single 808 nm NIR laser illumination to finally induce bacterial death.
Keywords: antibacterial; photothermal; quantum dots; reactive oxygen species; silver bismuth sulfide.