Optimization of the antibacterial activity of silver nanoparticles-decorated graphene oxide nanocomposites

Abstract

In this study, silver/graphene oxide (Ag/GO) nanocomposites were synthesized using the in situ method. Glucose was selected as an eco-friendly reducing agent for the reduction of Ag+ into silver nanoparticles (AgNPs). The characterization of GO and Ag/GO with Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopye, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Results showed that Ag/GO was successfully synthesized. Silver nanoparticles (AgNPs) with an average size of 17.68 ± 4.48 nm were uniformly distributed onto GO sheets. The antibacterial activity of GO, AgNPs, and Ag/GO were tested against Staphylococcus aureus ATCC 25,923 (S. aureus) and Salmonella enterica ATCC 35,664 (S. enterica) bacteria by optical density and plate colony–counting methods. Test results showed that Ag/GO had higher antibacterial activity than its precursors (bare AgNPs and GO) with a bactericidal rate of more than 99.90 %. Thus, Ag/GO was selected for further experimentation. Simultaneous effects of the interaction time, Ag/GO concentration, pH, annealing temperature, and S. aureus density on the antibacterial activity of Ag/GO were also investigated with full factorial experimental design according to Placket–Burman and Box–Behnken designs. After 10 min of interaction time at 37 °C, the optimal values of these factors were determined to be: Ag/GO concentration of 48 μg/mL, pH 5, and S. aureus density 5.3 × 106 CFU/mL, corresponding to an antibacterial capacity of 99.95 % towards S. aureus. The presented experiment confirmed Ag/GO to be able of eliminating about 99.99 % of S. aureus. All results of the present study affirmed the potential applications of Ag/GO as an antibacterial agent in the medical field.