In vitro evaluation of antioxidant, biochemical and antimicrobial properties of biosynthesized silver nanoparticles against multidrug-resistant bacterial pathogens

Interest in nanoparticles has increased rapidly over the last few years, becoming one of the most compelling scopes of research fields. The microbial methods utilized for biomediated nanoparticle synthesis are the most favourable and well-established substitute for the classic chemical and physical methods. In this study, silver nanoparticles (AgNPs) were biosynthesized by reducing Ag+ ions using a cell-free supernatant derived from Bacillus aerius culture and silver nitrate (AgNO3) solution as a precursor. The reaction mixture exhibited a colour change from yellow to brown, and ultraviolet-visible spectroscopy showed a surface plasmon resonance peak at 420 nm. The nanoparticles were monodispersed and spherical with an average particle size of 20.12-29.48 nm as determined by transmission electron microscopy. The Fourier transform infrared spectrum revealed the capping of AgNPs with biomolecular compounds that were responsible for the reduction of AgNO3 to AgNPs. The biosynthesized AgNPs had powerful and potent antibacterial activity against many multidrug-resistant bacterial pathogens. Moreover, the in vitro dose-dependent antioxidant activity of the aqueous extract of AgNP components showed good antioxidant activity as compared to the standard antioxidant ascorbic acid. These outcomes support the advantages of green techniques for synthesizing AgNPs that can be utilized effectively in the production of potential antioxidant and antibacterial AgNPs for commercial application.