Antibacterial Effects of Magnetically-Controlled Ag/Fe₃O₄ Nanoparticles

This paper presents the use of a magnetic manipulation device to remotely control the movement of Ag/Fe₃O₄ nanoparticles (NPs) for enhancing the antibacterial effect of Ag particles in aqueous suspensions containing Escherichia coli (E.coli). The Ag/Fe₃O₄ magnetic NPs were prepared by co-precipitation method where the Ag particles are simultaneously synthesized with the Fe₃O₄ particles to form Ag and Fe₃O₄ nanocomposite materials. The manipulation system utilized a homogeneous rotating magnetic field to carry out magnetic stirring of NPs in the petri dishes containing bacterial suspensions. The optimum magnetron parameters and best antibacterial effects were implemented with six different concentrations from 0.6 wt % to 6.6 wt % of the NPs at driving frequencies from 50 rpm to 200 rpm for 3 min. The highest antibacterial effect of 99.4% was achieved at 5.4 wt % of NPs and the driving frequency of 100 rpm. A time-dependent antibacterial effect in 0.1 wt % of Ag/Fe₃O₄ was also observed. The results indicate that the use of specific rotating magnetic fields to manipulate Ag/Fe₃O₄ magnetic NPs can significantly improve the antibacterial efficacy. Due to the good biocompatibility of the Ag NPs, the presented technique can be applied to clean water resources in the future.