Biogenic silver nanoparticles: Role of citric acid in nanoparticle stability and antimicrobial potency

Nanotechnology has enabled the synthesis of novel materials with remarkable properties. Among these, silver nanoparticles (AgNPs) synthesized via green method have emerged as an alternative eco-friendly approach with minimal waste product. This study investigates the synthesis of AgNPs at room temperature using grape leaf aqueous extract as a reducing agent and citric acid as a stabilizer and structure guiding agent. The effects of varying citric acid concentrations (10, 30, and 50 mM) on nanoparticle size, stability, and antimicrobial activity were examined. Characterization techniques, including SEM, EDS, UV-Vis, Raman spectroscopy, and XRD, confirmed successful nanoparticle formation. The absorption spectra of the synthesized samples showed SPR peaks between (420 nm-500 nm). The structure and shape of silver nanoparticles was greatly influenced by citric acid concentration. Antimicrobial assays against MRSA, E. coli , and Candida albicans revealed that AgNPs synthesized without citric acid exhibited strong activity, with inhibition zones of 17 mm, 15.5 mm, and 18.5 mm, respectively. The addition of 10 mM citric acid enhanced bacterial inhibition, with zones of 17.5 mm for MRSA and 16 mm for E. coli , and 17 mm for Candida albicans ). Higher citric acid concentrations (30 and 50 mM) led to nanoparticle aggregation and diminished antimicrobial efficacy. This study highlights the potential of optimizing citric acid levels to develop stable and effective AgNPs for medical and environmental applications.