Magnetic hybrid nanospindle with an unconventional force-thermal coupling antibacterial effect

Nanoplatforms have been considered as an effective strategy to address the resistance problem of traditional antimicrobial agents. This work reports a magnetic Fe₃O₄@AgAu@PDA (Fe₃O₄@AgAu@Polydopamine) antibacterial nanomaterial which possesses magnetically induced force-thermal coupling antibacterial effect. The polydopamine shell has good biocompatibility and the AgAu nanorods immobilized on the surface of the magnetic nanospindle not only create a rough surface for the anisotropic nanospindle but also endow it with high photothermal performance and oxidase-like/peroxide-like activities. Besides the original Ag ions release antibacterial activity, Fe₃O₄@AgAu@PDA nanospindles (80 μg/mL) also exhibit a good photothermal antibacterial effect (>90%) against Escherichia coli and Staphylococcus aureus under near-infrared (NIR) irradiation. Interestingly, when a rotating magnetic field (RMF) is applied, the antibacterial activity of the magnetic nanospindles can be further increased to nearly 100%. More importantly, in comparison to the Fe₃O₄@AgAu@PDA nanospheres, the Fe₃O₄@AgAu@PDA nanospindles exhibit a better antibacterial effect. By exploring the interaction between different particles and bacteria under magnetic field conditions, the basic mechanism of force-thermal coupling antibacterial was deeply explored and extended to biofilm removal. The results of cytotoxicity assay show that Fe₃O₄@AgAu@PDA nanospindles have good biocompatibility. Thus, the proposed strategy provides broad promise in antimicrobial therapy and biomedicine.