Tiopronin-AuAg@BCp12 Nanoclusters with Enhanced Aggregation-Induced Emission and Synergistic Antibacterial Effect

Herein, an effective antibacterial hybrid material was synthesized by covalently conjugating tiopronin with antibacterial gold and silver nanoclusters (TPN-AuAg NCs) and surface modification with the antimicrobial peptide BCp12. The as-synthesized TPN-AuAg@BCp12 exhibited not only the inherent performances with aggregation-induced emission (AIE) and antibacterial properties of its constituent agents but also a markedly augmented synergistic effect. A comparison of the antibacterial activities of TPN-AuAg@BCp12 NCs, TPN-AuAg NCs, and BCp12 revealed that TPN-AuAg@BCp12 NCs exhibited a more pronounced effect against Escherichia coli ( E . coli ) and Staphylococcus aureus ( S . aureus ) because of their dual antibacterial and biocompatibility properties. The minimum inhibitory concentrations of TPN-AuAg@BCp12 against E . coli and S . aureus were 32 μg·mL –1 and 1 mg·mL –1, and the minimum bactericidal concentrations were 128 μg·mL –1 and 2 mg·mL –1, respectively. Electrostatic affinity interactions occurred between the TPN-AuAg@BCp12 NCs and the wall membrane of E . coli or S . aureus, which damaged the cell wall membrane, resulting in the loss of bacterial integrity and leakage of intracellular substances to the outside of the cell, thereby inhibiting bacterial proliferation. Robust DNA destruction was facilitated by the localized accumulation of reactive oxygen species (ROS) induced by the targeted localization of the TPN-AuAg@BCp12 NCs. The conjugated TPN-AuAg@BCp12 NCs functioned as a critical source of free radicals, continuously producing ROS within the bacteria. Additionally, the notable fluorescence enhancement was attributed to an AIE pattern induced by TPN-AuAg@BCp12 NCs. This strategy offers a promising avenue for the synthesis of antibacterial agents and AIE-type fluorescent materials.