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 °C, 60 min and 10 mM AgNO3with 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.