Study On Recyclable Silver Loaded Magnetic Antibacterial Nanocomposites

Sliver nanoparticles (Ag NPs), as an important inorganic antibacterial agents, are particularly promising because of their unique bactericidal properties including high antibacterial activity, broad-spectrum antibacterial property and anti-drug resistance. Unfortunately, pure Ag NPs aggregate easily and remove from aqueous solution hard, greatly decreasing their antimicrobial efficiency. To solve these problems, selecting appropriate inorganic matrixes to load/decorate Ag NPs on is of importance. In this paper, two kinds of recyclable silver loaded magnetic nanomaterials with durable antibacterial ability were fabricated by anchoring Ag NPs onto Fe3O4 nanopaticles or graphene oxide (GO) respectively and introducing contact-killing chitosan (CS) quaternary ammonium salt polymer.Silver loaded chitosan modified magnetic nanoparticles (Fe3O4@ECS/PAA-Ag or Fe3O4@CS/PAEMA-Ag) were prepared by coating with ethylenediamine-modified chitosan/poly(acrylic acid) (ECS/PAA) or chitosan/poly (2-hydroethyl methacrylate) (CS/PAEMA) copolymeric layer, followed by attachment of Ag NPs. The composition and morphology of the resultant nanoparticles were confirmed by FT-IR, XRD, TEM and TGA. They dispersed well in water and displayed a good response to additional magnetic field, making the nanocomposites easy to recover from solution. Additionally, antibacterial testings (the inhibition zone test, the biocidal kinetic test and recycling antibacterial test) were conducted against both Gram-negative E. coli and Gram-positive S. aureus. Obvious inhibition zone around the silver loaded nanoparticles was observed, which demonstrated that silver ions were released in the presence of water. Both these two kinds of silver loaded chitosan modified magnetic nanocompsites possessed strong bactericidal activity with nearly 100% biocidal efficiency against both two species after contact 150 min, and exhibited higher antibacterial activity toward E. coli than toward S. aureus. Moreover, Fe3O4@ECS/PAA-Ag nanoparticles killed more than 99.72% E. coli and 99.63% S. aureus throughout ten cycles without washing with any solvents or water, exhibiting potent and durable antibacterial activity.Silver loaded magnetic graphene oxide nanocomposites (GO-Fe3O4@BNPVP-Ag) were synthesized by immobilizing Fe3O4 nanocomposites coupled with polymer quaternary ammonium salt (Fe3O4@BNPVP) and Ag NPs on the surface of graphene oxide. The composition and morphology of the resultant nanocomposites were confirmed by FT-IR, XRD, UV-Vis, TEM and Ramman. GO-Fe3O4@BNPVP-Ag nanocomposites exhibited excellent antibacterial properties against both Gram-negative E. coli and Gram-positive S. aureus. After contact 150 min, these two kinds of bacteria were totally inactivated. In addition, the data from the kinetic test and the values of MIC and MBC showed that graphene oxide decorated with Fe3O4@BNPVP and Ag NPs owned higher antibacterial activity than pure silver loaded graphene oxide, which further illustrated that BNPVP facilitated synergistic antibacterial effects.