Facile synthesis of tunable plasmonic silver core/magnetic Fe3O4 shell nanoparticles for rapid capture and effective photothermal ablation of bacterial pathogens

Multidrug-resistant (MDR) bacterial strains have emerged because of the widespread overuse of antibiotics. Thus, the development of new antibacterial materials and therapeutic methods to effectively kill bacteria is essential. A new type of silver core/magnetic Fe3O4 shell nanoparticle with strong magnetic responsiveness and tunable plasmonic properties (480–825 nm) has been developed as a multifunctional platform for bacterial disinfection. In this study, we firstly demonstrate that these Ag@Fe3O4–PEI NPs can be used as effective photothermal agents for simultaneous capture and photothermal killing of bacterial pathogens. Owing to the perfect combination of magnetic and photothermal properties in a single particle, the as-prepared Ag@Fe3O4–PEI NPs exhibit not only a wide range of bacterial capture abilities via electrostatic interaction between the positively charged magnetic Fe3O4 shell and the negatively charged bacterial cell wall but also outstanding photothermal antibacterial activity under NIR irradiation. The photothermal antibacterial tests show that even a concentration of 25 ppm of nanoparticles is enough to kill 100% of E. coli BL21 (107 CFU mL−1) in 10 min upon NIR irradiation. Furthermore, the Ag@Fe3O4–PEI NPs also show excellent photothermal stability, high magnetic recyclability, and low cytotoxicity. Therefore, we believe that these unique advantages make the as-prepared multifunctional core–shell nanocomposites very promising for biomedical sterilization applications.