A facile ultrasonication assisted method for Fe₃O₄@SiO₂-Ag nanospheres with excellent antibacterial activity

To increase the monodispersity of magnetic hybrid nanocomposites, a novel ultrasonic method was introduced to synthesize uniform Fe₃O₄@SiO₂-Ag nanospheres. The immobilized Ag nanocrystals were tunable by varying the experimental conditions. An antibacterial assay indicated that the Fe₃O₄@SiO₂-Ag nanospheres exhibited excellent antibacterial activities against Staphylococcus aureus and Escherichia coli, in which the minimum inhibition concentrations (MIC) were 40 μg mL^-1 and 20 μg mL^-1, respectively. The live/dead bacterial cell fluorescence stain assay agreed well with the antibacterial assay. The CCK-8 results indicated these nanospheres were bio-compatible for human normal cells and presented relative cytotoxicity against HepG2 tumor cells. These nanospheres could be easily uptaken by the cells and they could affect bacterial cells both inside and outside the cell membrane, which enable them to be promisingly applied in future biomedical areas.