Synthesis of Graphene Oxide-Silver Nanoparticle Nanocomposites: An Efficient Novel Antibacterial Agent

Background: Nanotechnology has become an essential and important field tool to develop various kinds of nanoparticles with high surface area to volume ratios and unique properties. Therefore, nanoparticles have been utilized for several biomedical applications; including diagnostics, drug delivery, biomarkers, and distinct antibacterial, antifungal and anti-biofilm agents. Silver nanoparticles (AgNPs) are known to be effective antibacterial agents and exhibit strong cytotoxicity against a broad range of microorganisms compared to conventional usage of silver salt and silver metal. The aim of this study was to synthesize graphene oxide- silver nanoparticle nanocomposites using a novel biomolecule called pepsin. Methods: The synthesized graphene oxide (GO) silver nanoparticle nanocomposite (GO-AgNPs) was characterized by ultraviolet-visible absorption spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The antibacterial and anti-biofilm activity of synthesized nanocomposite was evaluated using various assays, such as cell growth, cell viability, and reactive oxygen species generation. Results: The graphene oxide (GO)-silver nanoparticle nanocomposite (GO-AgNPs) was synthesized in the presence of AgNO3 and pepsin. The synthesized GO-AgNPs were characterized by various analytical techniques. The AgNPs were distributed uniformly on the surface of graphene oxide with an average size of 20 nm. Antibacterial activities of GO-AgNPs were evaluated by cell viability and anti-biofilm assay. GO, AgNPs and GO-AgNPs nanocomposites showed significant antibacterial activity against Shigella flexneri and Streptococcus pneumoniae. The loss of viability was observed in S. flexneri and S. pneumonia decreased in a dose-and time-dependent manner. GO-AgNPs showed significantly higher production of reactive oxygen species (ROS) compared to GO, AgNPs and the control, which is a possible mechanism of cell death. N-acetyl cysteine (NAC) significantly prevented cell death induced by GO, AgNPs, GO-AgNPs from oxidative stress in Shigella flexneri and Streptococcus pneumoniae via decreasing ROS generation. It suggests that elevated ROS is responsible for the loss of cell viability. Conclusion: Pepsin mediated GO-AgNPs could facilitate the simple, easy approach for large-scale production of graphene-based nanocomposites; GO-AgNPs exhibited an efficient and significant inhibitor for cell viability compared to GO, and silver nanoparticles. The nanocomposites could be effective antibacterial agents for the treatment of various infectious diseases.