Octopod-shaped silver-gold alloy for NIR-driven synergistic photothermal and catalytic bacterial ablation

The persistent threat of bacterial infections, which contribute to significant global morbidity and mortality, highlights the urgent demand for developing advanced antimicrobial materials. Herein, octopod-shaped silver-gold alloy nanostructures (Ag-Au octopods) were synthesized through a controlled deposition of gold onto silver octopods. Ag-Au octopods can convert near-infrared (NIR) light into thermal energy with photothermal conversion efficiency of 41.5 %. They also exhibited peroxidase-like nanozyme activity, catalysing the decomposition of trace amounts of H₂O₂ to produce significant levels of reactive oxygen species (ROS). Notably, this catalytic activity was further enhanced upon exposure to NIR light. During in vitro antibacterial tests, a dose of 32 µg mL^-1 of Ag-Au octopods, together with H₂O₂ and 10 min of NIR irradiation, achieved a bactericidal rate greater than 99.0 %. Mechanistic investigations revealed that the antimicrobial effect arises from the disruption of bacterial membrane integrity, leakage of intracellular nucleic acids, a rise in intracellular ROS, and subsequent oxidative stress. The results present an effective and synergistic antibacterial strategy using the combined photothermal and nanozyme activities, offering a promising direction for next-generation antibacterial applications.