Exopolysaccharide-mediated silver oxide nanoparticles from Bacillus cereus GV7: green synthesis, characterization, and antimicrobial, antibiofilm, antioxidant, and anticancer activities.

Exopolysaccharide-mediated silver nanoparticles (EPS-Ag2ONPs) were successfully biosynthesized using purified EPS from the marine sediment Bacillus cereus GV7. Among fourteen screened isolates, GV7 demonstrated the highest EPS production (83.7 ± 0.02 µg/mL) and was selected for Nanoparticle (NP) synthesis. EPS-Ag2ONPs were successfully synthesized under alkaline conditions, indicated by a characteristic colour change and subsequently UV-Vis spectroscopic analysis revealed a characteristic SPR peak at 424 nm. Further characterization using FTIR, SEM, EDX, XRD and AFM analysis confirmed the successful formation of spherical, well-dispersed, crystalline cubic Ag₂ONPs. SEM analysis revealed particle sizes ranging from 20 to 70 nm, whereas AFM analysis showed an average particle height of 5.09 nm. In this synthesis, EPS served as both a reducing and stabilizing agent. To our knowledge, no previous study has reported the biogenic synthesis of Ag2ONP using marine sediment-associated B. cereus GV7. Furthermore, the biosynthesized EPS-Ag2ONPs exhibited broad-spectrum antimicrobial efficacy against pathogenic microbes, with MIC values varied between 31.25 and 500 µg/mL. Significant antibiofilm activity was observed, with a maximum inhibition up to 84.54%, demonstrating effective disruption of biofilm formation. Dose-dependent antioxidant activity was demonstrated across DPPH, ABTS, FRAP, H₂O₂ scavenging, and total antioxidant capacity assays. Cytotoxicity evaluation against MG-63 human osteosarcoma cells by MTT assay revealed an IC50 value of 12.22 µg/mL, indicative of strong anticancer potential. These findings collectively signify EPS-Ag2ONPs from B. cereus GV7 as a promising multifunctional nanomaterial with potential biomedical applications.