Mesoporous polydopamine/copper sulfide hybrid nanocomposite for highly efficient NIR-triggered bacterial inactivation

Polydopamine has gained considerable attention in the biomaterial domain owing to its excellent biocompatibility, antioxidant activity, photothermal effect and adhesion property. Herein, copper sulfide (Cu 2-x S) wrapped in mesoporous polydopamine (MPDA) was synthesized through in-situ polymerization, followed by the surface modification with cationic polyethyleneimine (PEI). The mussel-inspired MPDA matrix successfully prevented the oxidation and agglomeration of Cu 2-x S nanoparticles, and regulated the release of copper ions and reactive oxygen species (ROS) levels. Surface-modified PEI endow MPDA@Cu 2-x S with positive charges, facilitating their rapid contact with negatively charged bacteria through electrostatic interactions. The pH-dependent Cu + /Cu 2+ release and NIR-responsive ROS generation were confirmed using molecular probes and electron spin resonance (ESR). The MPDA@Cu 2-x S/PEI showed significantly enhanced antibacterial activity and reduced cytotoxicity for NIH3T3 cells. Under NIR irradiation (1.0 W/cm 2 , 10 min), germicidal efficiency against Escherichia coli ( E. coli ) and Staphyloccocus aureus ( S. aureus ) could reach 100 % and 99.94 %, respectively. The exceptional antibacterial activities of MPDA@Cu 2-x S/PEI was mainly attributed to the synergistic photothermal effect, controlled release of copper ions and ROS generation, as well as electrostatic interaction. More importantly, the MPDA@Cu 2-x S/PEI composite exhibited excellent biocompatibility and biosafety. Overall, this organic/inorganic hybrid holds great potential as a promising candidate for wound treatment.