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

The biosynthesis and biological activity of colloidal AgO 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 AgO biosynthesis using Xanthomonas sp. P5. The optimal conditions for AgO synthesis were 50 °C, pH 8, and 2.5 mM AgNO. Using these conditions the yield of AgO obtained at 10 h was about five times higher than that obtained at 12 h under unoptimized conditions. AgO 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 AgO. AgO exhibited a broad antimicrobial spectrum against several human pathogens. Furthermore, AgO exhibited 1,1-diphenyl-2-picrylhydrazyl (IC = 25.1 µg/ml) and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonate (IC = 16.8 µg/ml) radical scavenging activities, and inhibited collagenase (IC = 27.9 mg/ml). Cytotoxicity of AgO was tested in fibroblast cells and found to be non-toxic, demonstrating biocompatibility.