Green synthesis of gold and silver nanoparticles using microalgae exopolysaccharides and evaluation of their antibacterial activity

In this research work, for the first time, gold and silver nanoparticles were successfully synthesized using exopolysaccharide extracted from the culture medium of porphyridium purpureum microalgae and then their antibacterial activity was evaluated. In this method, in addition to reducing the metal ions of gold and silver, exopolysaccharide also play a role in stabilizing the nanoparticles synthesized in aqueous solution. UV-Vis spectroscopy method was used to confirm the formation of synthesized nanoparticles. Also, transmission electron microscopy (TEM) was used to determine the size and morphology of the gold and silver nanoparticles synthesized using microalgae exopolysaccharide. Finally, the antibacterial activity of nanoparticles synthesized using exopolysaccharide derived from microalgae was evaluated on two types of gram-positive bacteria (E. Faecalis) and gram-negative bacteria (E. coli). For this purpose, disk diffusion test was used, as a result of which it was found that these stabilized nanoparticles have significant antibacterial activity. Exopolysaccharide-stabilized silver nanoparticles also show better antibacterial activity than exopolysaccharide-stabilized gold nanoparticles.