Green synthesis of silver nanoparticles using turmeric extracts and investigation of their antibacterial activities

This study aimed to develop an environmentally friendly and cost-effective approach to synthesize green silver nanoparticles (AgNPs) from silver precursors. Green synthesis of AgNPs was accomplished using the aqueous extract of turmeric powder, in which plant biomaterials were used as a reducing as well as a capping agent. After 24 h of reaction, the yellow color of the extract was changed to dark brown-reddish due to the reduction of silver ions to AgNPs. AgNPs were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The maximum absorbance of the UV-vis spectra was at 432 nm. TEM analysis reveals that the shape of most of the biosynthesized AgNPs was spherical forms and the average particle size was 18 +/- 0.5 nm. EDS analysis exhibits strong signals of silver element. In addition, green synthesized AgNPs show high and efficient antimicrobial activities against two food-borne pathogens (Escherichia coil O157:H7 and Listeria monocytogenes). TEM and scanning electron microscopic images reveal that there were significant shrinkage and damage of bacterial cell wall, and leakage or loss of bacterial intracellular contents. A significant reduction (P <= 0.05) of bacterial counts just after 4 h of exposure was observed. These results indicate that green synthesized AgNPs can be utilized as an antimicrobial means to inhibit the growth of pathogenic bacteria for applications in agricultural and food industries.