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 (CuS) 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 CuS nanoparticles, and regulated the release of copper ions and reactive oxygen species (ROS) levels. Surface-modified PEI endow MPDA@CuS with positive charges, facilitating their rapid contact with negatively charged bacteria through electrostatic interactions. The pH-dependent Cu/Cu release and NIR-responsive ROS generation were confirmed using molecular probes and electron spin resonance (ESR). The MPDA@CuS/PEI showed significantly enhanced antibacterial activity and reduced cytotoxicity for NIH3T3 cells. Under NIR irradiation (1.0 W/cm, 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@CuS/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@CuS/PEI composite exhibited excellent biocompatibility and biosafety. Overall, this organic/inorganic hybrid holds great potential as a promising candidate for wound treatment.