Characterization and antibacterial activity of silver nanoparticles prepared with a fungal exopolysaccharide in water

This work demonstrates a simple and feasible approach for the synthesis of silver nanoparticles (AgNPs) in water with a high molecular weight (MW) exopolysaccharide fraction, EPS1 produced by a medicinal fungus Cs-HK1. The formation and properties of AgNPs were evaluated at various temperatures, time periods, and silver nitrate/EPS1 concentrations in water. At suitable conditions (100 degrees C, 60 min and 10 mM AgNO3 with 1.0 mg/mL EPS1), AgNPs were formed with an average diameter of 50 nm and a narrow size distribution, remaining as a stable dispersion for at least 2 months. EPS1 may be acting as a reducing and stabilizing agent for the formation of AgNPs, which were attached to the hydroxyl groups of EPS1. The AgNPs formed in EPS1 solution exhibited a concentration-dependent inhibition of both Gramnegative and -positive bacteria but a very low cytotoxicity on the RAW264.7 murine macrophage cells. The results demonstrated the feasibility for green synthesis of AgNPs as potential antibacterial agents using natural polysaccharides dissolved in water. (C) 2015 Elsevier Ltd. All rights reserved.