One-dimensional rough magnetic nanochains as magnetically actuated mechano-antibacterial materials

The growing prevalence of antibiotic-resistant bacteria has driven increasing interest in non-chemical antibacterial strategies that rely on physical mechanisms rather than biochemical toxicity. However, the rational construction of nanomaterials that can efficiently convert external stimuli into localized mechanical forces at bio-interfaces, while maintaining structural stability and biocompatibility, remains a major challenge. Here, we report a magnetic-field-assisted interfacial co-assembly and epitaxial growth strategy to construct a one-dimensional hierarchical magnetic nanochain with a rough silica shell (denoted as the Fe₃O₄@rSiO₂ nanochain), enabling a remotely actuated mechano-antibacterial platform. In this system, spherical Fe₃O₄ nanoparticles are aligned into anisotropic nanochains under a magnetic field and subsequently encapsulated by a hierarchically rough SiO₂ shell, integrating magnetic responsiveness, directional geometry, and mechanically active surface topology within a single nanostructure. Under an alternating magnetic field, the nanochains undergo efficient rotational motion, converting magnetic torque into localized shear forces at the nanochain-bacteria interface. The rough silica surface further enhances the stress concentration and adhesion, thereby rapidly reducing the surface Young's modulus of E. coli from the normal value of 1876 kPa to 200 kPa without relying on chemical disinfectants, ion release or thermal effects. The nanochains exhibit superior antibacterial efficacy in vitro and effectively accelerate wound healing in an infected murine model while maintaining excellent biocompatibility and recyclability. This work establishes a general design paradigm for magnetically actuated mechano-active nanomaterials, demonstrating how field-directed assembly combined with hierarchical surface engineering can transform passive nanostructures into programmable antibacterial agents. The strategy presented here is readily extendable to other material systems and bio-interfacial applications, offering new opportunities for non-chemical antimicrobial and biomedical technologies.