Facile Preparation of Nanosilver Particles with Excellent Antimicrobial Activity via Release of Ionic Silver

Nanosilver particles (SNPs) have been widely exploited in various fields, including the medical sciences due to their excellent inhibitory and bactericidal effects. It is of great importance to prepare SNPs using green synthesis that has environmentally acceptable solvent systems and eco-friendly reducing agents. In the current study, gallic acid was employed as both a reducing agent and a stabilizing agent to synthesize SNPs at mild ambient conditions. The image of transmission electron microscopy (TEM) showed that SNPs exhibited approximately spherical shape with the average diameter of 13.81 +/- 2.21 nm. The absorbance peak of obtained SNPs was sharp with the maximum wavelength of 400.5 nm by ultraviolet-visible (UV-vis) spectroscopy, suggesting the formation of small and highly monodispersed SNPs. The antimicrobial potential of the SNPs was evaluated against multiple common pathogenic microbes. The results indicated that the microbial sensitivity to the SNPs was found to vary depending on the microbial species. Among them, the gram-negative bacteria exhibited more sensitive toward SNPs than the gram-positive bacteria. In addition, the N-acetyl-L-cysteine (NAC), a silver ion chelator, pretreatment could protect the E. coli and P. aeruginosa from the SNPs inhibition, while the pretreatment of the L-ascorbic acid, an antioxidant against oxidative stress, did not significantly influence the antibacterial effects of the SNPs. These data suggested that the ionic silver release, but not reactive oxygen species (ROS), played a key role in the antimicrobial effect of the SNPs. To sum up, this study provides an environmentally friendly technique for facile synthesis of SNPs with excellent antibacterial potential.