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 <i>Crassula ovata</i> (Jade) leaf extract, <i>Bacillus licheniformis</i> 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: <i>Escherichia coli</i>, <i>Pseudomonas aeruginosa</i>, <i>Staphylococcus epidermidis</i>, and Methicillin-resistant <i>Staphylococcus aureus</i> (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 <i>E. coli</i>, 12.5 µg/mL for <i>P. aeruginosa</i>, 10 µg/mL for <i>S. epidermidis</i>, and 15 µg/mL for MRSA. The bacterial supernatant-synthesized AgNPs showed MBC values of 10 µg/mL for <i>E. coli</i>, 12.5 µg/mL for <i>P. aeruginosa</i>, 7.5 µg/mL for <i>S. epidermidis</i>, and 12.5 µg/mL for MRSA. In contrast, citrate-reduced AgNPs exhibited higher MBCs: 60 µg/mL for <i>E. coli</i> and <i>P. aeruginosa</i>, 40 µg/mL for <i>S. epidermidis</i>, 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.