Abstract
Herein, a new and simple biogenic method for the preparation of gold nanoparticles (AuNPs) and their reduced graphene oxide based nanocomposites (Au-RGO) by using microwave irradiation method for antimicrobial and biofilm inhibition against foodborne pathogenic bacteria was reported. X-ray diffraction (XRD), Raman, and transmission electron microscopy (TEM) analyses confirmed that the AuNPs with face centered cubic (FCC) structure were indeed anchored onto the RGO sheets. Ultraviolet-Vis (UV-VIS) spectrum showed a shifting and broadening of absorption peaks of AuNPs when attached on the surface of RGO sheets. The effect of sub-inhibitory concentrations of Au-RGO nanocomposites on biofilm formation in five foodborne pathogens was assessed. Au-RGO nanocomposites reduced the formation of biofilm by 75%, 78%, 68%, 80% and 79% in L. monocytogenes, MRSA, E. coli, S. marcescens and P. aeruginosa, respectively. Exopolysaccharides (EPS), a vital component of the biofilm was also inhibited significantly and pre-formed mature biofilms were also reduced considerably. Further, this study demonstrated that the reactive oxygen species (ROS) generation induced in bacterial cells as a result of Au-RGO treatment could be the plausible mechanism for biofilm inhibitory action. The tested concentrations were found non-toxic to human embryonic kidney cell lines (HEK-293). The investigation highlights the broad-spectrum biofilm inhibitory properties of Au-RGO nanocomposites that could be exploited in the food industry to prevent biofilm-based food contamination.