Copper nanoclusters with aggregation-induced emission: an effective photodynamic antibacterial agent for treating...

Designing antibacterial agents with broad-spectrum antibacterial effects and resistance-free properties is essential for treating bacteriainfected wounds. In this study, we present the design of copper nanoclusters (Cu NCs) that exhibit aggregation-induced emission (AIE). This was achieved by controlling the aggregation state of ligand layers (cysteine and chitosan) through the manipulation of pH and temperature. The AIE properties, characterized by strong photoluminescence (PL), a large Stokes shift, and microsecond-long lifetimes, enable these Cu NCs to generate significant amounts of reactive oxygen species (ROS) upon light illumination for efficient bacterial elimination without inducing drug resistance. As a result, they effectively inactivate various microbial pathogens, including Gram-negative and Gram-positive bacteria, as well as Candida albicans (C. albicans), achieving elimination rates of 99.52% for Escherichia coli (E. coli), 98.89% for Staphylococcus aureus (S. aureus), and 94.60% for C. albicans in vitro. Furthermore, the natural antibacterial properties of chitosan and Cu species enhance the photodynamic antibacterial efficacy of the AIE-typed Cu NCs. Importantly, in vivo experiments demonstrate that these Cu NCs can effectively eradicate bacteria at infection sites, reduce inflammation, and promote collagen synthesis, facilitating nearly 100% wound recovery in S. aureus-infected wounds within 9 days. The findings of this study are of considerable significance, providing a foundation for the application of AIE-typed Cu NCs in photodynamic nanotherapy for bacterial infections.