Biogenic vs. Chemical AgNPs: A Comparison of Antimicrobial Potency and Stability

This study presents a comprehensive evaluation of the antimicrobial activities of silver nanoparticles (AgNPs) synthesized using three distinct methods: plant extracts, bacterial supernatant, and a conventional chemical method. AgNPs were synthesized from Crassula ovata (Jade) leaf extract, Bacillus licheniformis bacterial supernatant, and a standard chemical reduction method using trisodium citrate. The synthesized AgNPs were characterized using UV-Vis spectroscopy, Transmission Electron Microscopy (TEM), and Dynamic Light Scattering (DLS). The antimicrobial efficacy of the AgNPs was tested against four pathogenic microorganisms: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Methicillin-resistant Staphylococcus aureus (MRSA). Our findings reveal significant differences in the biological activities of the AgNPs depending on the synthesis method. The MBC values for the plant extract-synthesized AgNPs were 10 µg/mL for E. coli, 12.5 µg/mL for P. aeruginosa, 10 µg/mL for S. epidermidis, and 15 µg/mL for MRSA. The bacterial supernatant-synthesized AgNPs showed MBC values of 10 µg/mL for E. coli, 12.5 µg/mL for P. aeruginosa, 7.5 µg/mL for S. epidermidis, and 12.5 µg/mL for MRSA. In contrast, citrate-reduced AgNPs exhibited higher MBCs: 60 µg/mL for E. coli and P. aeruginosa, 40 µg/mL for S. epidermidis, and 80 µg/mL for MRSA. Notably, the AgNPs synthesized using plant and bacterial supernatant demonstrated superior antimicrobial activity compared to those synthesized chemically. This comparative study highlights the potential of eco-friendly synthesis routes for producing AgNPs with enhanced biological activities. The findings suggest that plant extract and bacterial supernatant-mediated synthesis of AgNPs could serve as a viable and sustainable alternative to conventional chemical methods, offering promising applications in medical and pharmaceutical fields.