Mussel-inspired mesoporous polydopamine coated bismuth sulfide nanocomposites with excellent photothermal conversion, antibacterial and antioxidant properties

The scarcity of antibiotic alternatives has posed a serious threat of the global spread of antibiotic-resistant bacteria. Achieving a delicate balance between antibacterial activity and anti-inflammatory efficacy within infected tissues is crucial for promoting efficient wound healing. Herein, a novel near-infrared (NIR)-responsive nanomaterial (BSMC NPs) is fabricated via the in-situ growth of mesoporous polydopamine (MPDA) on the surface of Bi 2 S 3 , followed by the loading of curcumin (Cur) into the mesopores and onto the surface through π-π stacking interactions. This organic-inorganic hybrid system exhibits excellent photothermal conversion efficiency as well as prominent antioxidant capacity. Upon NIR light irradiation, the photothermal effect triggers the generation of reactive oxygen species (ROS) by both Bi 2 S 3 and MPDA, thereby enabling efficient bacterial eradication. Conversely, in the absence of light stimulation, the inherent antioxidant properties of MPDA and Cur allow for the rapid scavenging of excessive ROS, thus exerting potent anti-inflammatory effects. The pH- and NIR-dual responsive release profile of Cur has been experimentally verified. Antibacterial assays reveal that BSMC NPs achieve inhibition rates of 98.5 % against Staphylococcus aureus ( S. aureus ) and 92.4 % against Escherichia coli ( E. coli ) under 808 nm laser irradiation. The underlying antibacterial mechanism is attributed to the increased permeability of bacterial membranes and leakage of intracellular contents, which are induced by localized hyperthermia and ROS burst. Collectively, this work provides novel insights into the rational design of multifunctional biomaterials integrating antioxidant, antibacterial, and photothermal therapeutic functionalities.