Silver nanoparticle and lysozyme/tannic acid layer-by-layer assembly antimicrobial multilayer on magnetic nanoparticle by an eco-friendly route.

A facile, economical and green synthetic route was developed to fabricate magnetic nanocomposite arming with silver nanoparticles (AgNPs) for antibacterial application. In this synthesis, two natural compounds, positively charged lysozyme (Lys) and negatively charged tannic acid (TA), were alternately deposited on Fe3O4 nanoparticles (IONPs) surface by layer-by-layer (LbL) self-assembly technique. And then AgNPs were embedded by an in situ reduction of Ag+ so as to achieve complementary antibacterial functions to act against Gram-positive and Gram-negative bacteria. In which, the deposition of AgNPs can be facilely achieved without any external reducing agent. The systematic antibacterial assays showed that synthesized nanocomposites had high antibacterial efficiency against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Investigation of antimicrobial mechanism suggested that these nanocomposites could lead to the disorganization of bacterial cytomembrane and leakage of cytoplasmic contents. Moreover, the permeable alteration of cytoplasmic membrane may facilitate the Ag+ released from nanocomposite entering into cells, and further cause the bacterial death. Due to the excellent magnetic responsive performance of IONPs, the nanocomposites can be easy recovery by external magnetic field from application environment after disinfection. By taking advantages of such properties, the developed nanocomposite could be an ideal candidate with promising antibacterial applications.