Synergistic antibacterial activity of PEGylated silver–graphene quantum dots nanocomposites

Abstract

The emergence of antibiotic-resistant bacteria is a major threat to world-wide public health. Function-alized nanoparticles could offer novel strategies in this post-antibiotic era. In this study, we developed nanocomposites of silver nanoparticles decorated with graphene quantum dots (Ag-GQDs) using pulsedlaser synthesis. The nanocomposites were PEGylated, which increases their biocompatibility and solu-bility in aqueous solutions. The HR-TEM micrographs of bare GQDs show that their size is in the range of1.6–4 nm, and the lattice spacing is 0.214 nm, which corresponds to the (1 0 0) lattice fringes of graphene.The antibacterial activity of Ag-GQDs was evaluated and compared to that of bare GQDs and commercial silver nanoparticles (Ag-NPs) against both Gram-negative and Gram-positive bacteria, using Pseudomonasaeruginosa and Staphylococcus aureus as model bacteria, respectively. Concentration values of 25 and50 g/mL are required for Ag-GQDs to inhibit the growth of S. aureus and P. aeruginosa bacteria, respectively. The fractional inhibitory concentration (FIC) index is below 0.5 indicating that there is a synergisticeffect between Ag-NPs and GQDs. Kirby–Bauer tests showed that Ag-GQDs inhibit P. aeruginosa and S.aureus, in contrast to bare GQDs and Ag-NPs alone. Cell viability of normal mammalian cells treatedwith Ag-GQDs showed that cell viability is maintained at 100% for cells incubated with Ag-GQDs. Thedecoration of Ag-NPs with GQDs minimizes their cytotoxicity in mammalian cells and increases their bio-compatibility. Ag-GQDs have potential applications in the fabrication of antibacterial coatings, self-sterile textiles, and personal care products.