Biogenic synthesis and characterization of silver nanoparticles: exploring antioxidant and anti-Inflammatory activities and assessing antimicrobial potential against multidrug-resistant bacteria

Multi-drug resistant (MDR) bacterial infections significantly increase mortality, morbidity, and treatment costs when they persist. Therefore, there is a pressing need to discover, modify, or search for antimicrobial agents with the ability to combat MDR bacteria. Silver nanoparticles used in this study were synthesized by Bacillus subtilis and characterized through different techniques. MDR strains underwent antibacterial activity, antioxidant activity, and time-kill kinetic assays to assess susceptibility to silver nanoparticles. Furthermore, the synergistic impact of silver nanoparticles and antibiotics was examined using the two-dimensional checkerboard method to calculate the Fractional Inhibitory Concentration Index (FICI). Scanning Electron Microscopy (SEM) results revealed a circular shape of synthesized AgNPs, with an average length and area of 76.78 and 47.10 nm, respectively. UV analysis showed an optimum peak at 420 nm. XRD analysis indicated the crystalline nature of nanoparticles with diversity in size. Remarkable antioxidant potential (55% of AgNPs) was observed at a concentration of 1000 mu g/ml, while minimum activity (18%) was noted at 62.6 mu g/ml. Silver nanoparticles demonstrated a synergistic interaction with the antibiotic Cefixime against Staphylococcus aureus , Acinetobacter baumannii , Escherichia coli , and Klebsiella pneumoniae , with FICI values of 0.37, 0.3, 0.25, and 0.49, respectively, and an additive effect against Pseudomonas aeruginosa , with a FICI value of 0.7. Moreover, this research explores the antiinflammatory potential of silver nanoparticles (AgNPs) in two distinct models: formaldehyde-induced inflammation and carrageenan-induced inflammation, along with an assessment of their in vitro anti-inflammatory activity. The findings shed light on the multifaceted role of AgNPs in mitigating inflammatory responses, offering promising avenues for therapeutic interventions.