Prajapati N.B. and Raval A.A.
Abstract
The present study explores the eco-friendly biosynthesis of silver nanoparticles (AgNPs) using an endophytic bacterial isolate EC1 obtained from Capsicum annuum. The synthesis was carried out using bacterial cell-free supernatant, where a visible color change confirmed nanoparticle formation due to surface Plasmon resonance. Optimization studies revealed that neutral pH (7), temperature of 45 °C, and a 5:5 ratio of supernatant to AgNO3 were optimal for nanoparticle production. UVâVisible spectroscopy exhibited a characteristic absorption peak at ~430 nm, confirming AgNP formation. SEM analysis revealed predominantly spherical to quasi-spherical nanoparticles with a size range of 22â30 nm. Dynamic light scattering analysis showed an average hydrodynamic size of 98.53 nm with a polydispersity index of 0.223, while zeta potential analysis indicated good stability with a value of â31.9 mV. The biosynthesized AgNPs demonstrated significant antimicrobial activity against various plant pathogens, including Pythium spp., Fusarium spp., Rhizoctonia solani, and bacterial species such as Xanthomonas campestris and Pseudomonas syringae. Antioxidant activity assessed by DPPH assay showed moderate free radical scavenging potential with inhibition values up to 26.96%. Furthermore, cytotoxicity studies using the MTT assay revealed a dose-dependent decrease in cell viability in both NIH3T3 (normal) and MCF-7 (cancer) cell lines, with enhanced sensitivity observed in cancer cells, indicating potential selective cytotoxicity. Overall, the findings suggest that EC1-derived AgNPs possess promising antimicrobial, antioxidant, and anticancer properties, highlighting their potential applications in biomedical and agricultural fields. The study emphasizes the effectiveness of green synthesis as a sustainable approach for nanoparticle production.