Ag colloids and Ag clusters over EDAPTMS-coated silica nanoparticles: synthesis, characterization, and antibacterial activity against Escherichia coli

To produce better antibacterial water-insoluble nanocomposites of silver (Ag), silver-silicon dioxide (Ag-SiO2) hybrid and silver colloid (Ag-c) nanoparticles (NPs) were studied. Ag-c NPs were synthesized using reduction of AgNO3, and Ag-SiO2 composites were prepared on a core of silica NPs functionalized with ethylenediamino-propyltrimethoxysilane, where Ag clusters were fabricated on amino groups using seed-mediated growth and characterized by transmission electron microscopy and ultraviolet-visible absorption spectroscopy. Antibacterial effectiveness of the Ag-SiO2 NPs was tested against general Escherichia coli (E. coli ATCC 25922) and E. coli O157:H7 by measuring the growth based on optical density and digital counting of live-dead cells using a fluorescent microscope, and a field emission scanning electron microscope. Minimum inhibitory concentration values were studied against four representative bacteria along with E. coli O157:H7. Results showed that Ag NPs of 6.6 +/- 4.5 nm were attached to the surface of SiO2 NPs (74 +/- 13.5 nm), and the Ag-c NPs (3.5 +/- 2 nm) showed excellent antibacterial properties. From the Clinical Editor:In this paper, the synthesis of Ag colloids and Ag clusters over EDAPTMS-coated silica nanoparticles is reported. Both NPs were examined for antibacterial effectiveness against representative bacteria including E. coli O157:H7 and found to have excellent antibacterial properties. (C) 2011 Elsevier Inc. All rights reserved.