Polyethylenimine Mediated Ferroferric Oxide-reduced Graphene-silver Nanocomposite As A Promising Photothermal Antibacterial Agent

With increasing concerns on bacterial infections,there is a growing need to develop new and powerful antibacterial agents.It is known that silver nanoparticles(Ag-NPs)have shown excellent effective antibactericidal properties,but the applications of Ag-NPs for antibacterial treatment are still limited due to probably their low stability and the feature of ease of aggregation.Herein,a novel bactericidal material,Ag@rGO-Fe3O4-PEI composite,is prepared,by in-situ growth of silver nanoparticles onto the polyethylenimine(PEI)mediated magnetic reduced graphene oxide(rGO).In the present work,we report a new antibacterial agent by a three-step procedure.Firstly,GO is prepared from graphite powder according to the modified Hummer's method.Then PEI mediated rGO-Fe3O4 magnetic composite.The magnetic rGO-Fe3O4-PEI composite is prepared followed by in-situ growth of Ag-NPs onto its surface to construct the Ag@rGO-Fe3O4-PEI magnetic composite.Ag@rGO-Fe3O4-PEI composite is characterized by UV-vis,FT-IR,scanning electron microscope(SEM),X-ray diffraction(XRD)and transmission electron microscope(TEM).The results indicate that the antibacterial properties of the Ag@rGO-Fe3O4-PEI composite are excellent at Ag/rGO-Fe3O4-PEI mass ratios of 15 and 20.Graphene oxide(GO)is able to capture the bacteria and make silver nanoparticles well dispersed.The antibacterial performances of the composite are investigated by using Gram-negative bacteria Escherichia coli 0157:H7(E.coli 0157:H7)as a model.The results indicate that the Ag@rGO-Fe3O4-PEI composite exhibits excellent antibacterial performance against E.coli 0157:H7,with a superior antibacterial performance to those for the ever reported photothermal materials.The bactericidal capability or the inhibition capability for bacteria growth is found to depend on the dosage of Ag@rGO-Fe3O4-PEI and Ag/rGO-Fe3O4-PEI mass ratio within certain range.By using a dosage of 0.1 ?g mL-1,a killing rate of 99.9%is achieved for the E.coli 0157:H7(106?107 cfu mL-1)under a 0.5 min NIR laser irradiation(785 nm/50 mW cm-2).In addition,a minimum bactericidal concentration(MBC)of 0.100 ?g mL-1 is achieved under NIR laser irradiation for 10 min,for which case there is completely no colony of E.coli 0157:H7 found in the broth agar plate.