Bacterial indoleacetic acid-induced synthesis of colloidal Ag2O nanocrystals and their biological activities.

ABSTRACT

The biosynthesis and biological activity of colloidal Ag2O nanocrystals have not been well studied, although they have potential applications in many fields. For the first time, we developed a reducing agent free, cost-effective technique for Ag2O biosynthesis using Xanthomonas sp. P5. The optimal conditions for Ag2O synthesis were 50 °C, pH 8, and 2.5 mM AgNO3. Using these conditions the yield of Ag2O obtained at 10 h was about five times higher than that obtained at 12 h under unoptimized conditions. Ag2O was characterized by FESEM-EDS, TEM, dynamic light scattering, XRD, and UV-Visible spectroscopy. Indoleacetic acid produced by the strain P2 was involved in the synthesis of Ag2O. Ag2O exhibited a broad antimicrobial spectrum against several human pathogens. Furthermore, Ag2O exhibited 1,1-diphenyl-2-picrylhydrazyl (IC50 = 25.1 µg/ml) and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonate (IC50 = 16.8 µg/ml) radical scavenging activities, and inhibited collagenase (IC50 = 27.9 mg/ml). Cytotoxicity of Ag2O was tested in fibroblast cells and found to be non-toxic, demonstrating biocompatibility.