Reduced Graphene Oxide Nanosheets Decorated with Au Nanoparticles as an Effective Bactericide: Investigation of Biocompatibility and Leakage of Sugars and Proteins

This article reports the synthesis of a composite of reduced graphene oxide nanosheets decorated with gold nanoparticles (AuNPs-rGO) through an ecofriendly route, and the investigation of its biocompatibility to HeLa cells and its antibacterial activity against Gram-positive and Gram-negative bacteria. The composite material is synthesized by using an environmentally friendly reducing agent, ascorbic acid, under ultrasonication. The composite material is characterized by UV/Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), high-resolution transmission electron microscopy (HRTEM), and thermogravimetric analysis (TGA). HRTEM analysis reveals the formation of spherical Au NPs of 8–45 nm in size on the folded rGO nanosheets, which is further confirmed by XRD and SAXS analyses. The AuNPs-rGO shows good biocompatibility with cervix carcinoma, human (HeLa) cells, and possesses high antibacterial activity against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-negative bacteria (Escherichia coli and Pseudomonous aeruginosa). The bacterial cell death is caused by the leakage of sugars and proteins from the cell membrane in contact with the AuNPs-rGO composite material.