Systematic Control of Silver Nanoparticle Size and Shape for Enhanced Biocompatibility and Antibacterial Activity against Staphylococcus aureus and Escherichia coli

Abstract The antimicrobial activity of silver nanoparticles (AgNPs) is strongly influenced by their size and shape. This study investigates the impact of synthesis conditions on the morphology and antibacterial properties of AgNPs against Staphylococcus aureus and Escherichia coli. Six synthesis routes were tested using sodium borohydride, ascorbic acid, and sodium citrate as reducing agents, yielding nanoparticles with diverse structures, including spherical, ellipsoidal, truncated cubes, polyhedral, and elongated bars. Morphological differences were confirmed by TEM and UV-Vis spectroscopy. The overall results showed that quasi-spherical AgNPs synthesized using sodium borohydride at low temperatures and ascorbic acid at room temperature yielded the best MIC and % hemolysis, 2,75 E−3 ng/mL and 5,49 E−4 ng/mL, respectively, likely due to greater surface reactivity. Hemolysis assays suggested that nanoparticles produced at lower temperatures exhibited reduced cytotoxicity. These results highlight the importance of controlling synthesis parameters to optimize the antimicrobial effectiveness and biocompatibility of AgNPs for biomedical applications, particularly against bacteria that have a negative impact on human health.