Anisotropic α-Fe₂O₃/AgAu/Polydopamine Nanostructures for Photothermally Enhanced Antibacterial Applications

Multifunctional photothermal nanomaterials offer notable opportunities for antimicrobial therapy due to their excellent antibacterial activities without leading to drug resistance. Herein, we report a facile one-step strategy for fabricating anisotropic corn-like α-Fe₂O₃/AgAu/polydopamine (PDA) nanospindles with photothermally enhanced antibacterial performance. The AgAu bimetallic nanocrystals sandwiched between the α-Fe₂O₃ core and the PDA shell are achieved by simultaneous reduction from AgNO₃ and HAuCl₄ during the oxidative polymerization of dopamine and galvanic replacement reaction between the obtained Ag nanocrystals and Au precursor. The inner nanostructure and atom ratio of AgAu bimetallic nanocrystals can be modulated by varying the experimental parameter, thus further controlling the photothermal activities. In comparison to α-Fe₂O₃/Au/PDA, Fe₂O₃/Ag_1.7Au_0.8/PDA (50 μg/mL) has a better photothermal conversion effect (60.69%). Moreover, the α-Fe₂O₃/Ag_1.7Au_0.8/PDA nanospindle exhibits moderate antibacterial activity, which may be derived from Ag⁺ release. Under application of near-infrared light irradiation, the corn-like α-Fe₂O₃/Ag_1.7Au_0.8/PDA nanospindles (50 μg/mL) exhibit a photothermally enhanced sterilization effect against both Escherichia coli and Staphylococcus aureus (99.99%). This “Ag⁺ release-photothermal” coupling sterilization method provides a simple synergistic antimicrobial therapy strategy, which possesses great promise for future nanomedicine against bacteria in water treatment.