Magnetically Recyclable Core–Shell Ag@Fe3O4 Nanoparticles for Waterborne Pathogen Inactivation and Medical Biofilm Eradication

The proliferation of drug-resistant bacteria in water poses a significant public health threat. Experimental wastewater from microbiology laboratories and residual fluids in medical catheters are particularly prone to pathogenic bacterial growth and biofilm formation. This challenge requires antibacterial agents that can eliminate pathogenic bacteria with high efficiency. In this study, core–shell Ag@Fe3O4 NPs were synthesized via a straightforward solvothermal method. This structuration minimizes silver ion loss and ensures sustained antibacterial activity through core–shell synergy. Mechanistic studies revealed that Ag@Fe3O4 disrupts biofilm architecture and induces nucleic acid leakage via the synergistic release of Ag+ ions and the generation of reactive oxygen species (ROS). Significantly, Ag@Fe3O4 NPs exhibit superparamagnetic properties and demonstrate a low minimum inhibitory concentration (MIC) of 10 μg/mL. In water treatment simulations, Ag@Fe3O4 NPs maintained a 100% pathogen elimination rate across diverse environmental conditions after 40 magnetic recovery cycles. Furthermore, the Ag@Fe3O4 NPs achieved precise targeting and efficient removal of biofilms in a medical catheter model under magnetic guidance. Ag@Fe3O4 NPs offer an efficient and sustainable solution for eradicating waterborne pathogens and eliminating medical catheter biofilms.