Magnetic field-driven nanospears for enhancing antibacterial strategy.

Antimicrobial resistance poses a significant challenge to global health, necessitating innovative strategies to combat bacterial infections. This study introduces a novel approach that combines the mechanical effects of magnetically-driven nanospears with photothermal action to enhance bacterial eradication efficacy. The anisotropic FeO@PDA nanorobots with controllable aspect ratios are synthesized by encapsulating strong magnetic FeO nanospears with polydopamine (PDA), which exhibits high near-infrared (NIR) photothermal efficiency. Because the sharp tips on the FeO@PDA nanospears concentrate mechanical stress on bacterial membranes, they exhibit enhanced antibacterial activity when a rotating magnetic field (RMF) is applied to increase the mechanical damage. Notably, the combination of RMF and NIR irradiation markedly enhance biofilm removal and bacterial inactivation, especially against Staphylococcus aureus. The aspect ratio is found to have a high influence on the coupling effect, and the ellipsoidal nanoparticles without the sharp tips exhibit a significantly reduced effect compared to the nanospears. The piercing effect of nanospears on bacterial membranes and the synergistic impact of mechanical penetration and photothermal treatment are clearly observed via experimental analysis. Finite element analysis (FEA) and coarse-grained molecular dynamics (CGMD) simulations further confirm that the nanospears can effectively penetrate bacterial membranes and the elevated temperatures amplify membrane disruption. This photothermal-magnetomechanical synergistic effect offers a promising and function-tailored strategy to address antimicrobial resistance, positioning nanospears as a viable alternative to conventional antibacterial treatments.