Enhancement of Microbial Synthesis of Gold Nanoparticles by Gamma Radiation

Aim: An eco-friendly protocol for the synthesis of gold nanoparticles (GNPs) using submerged liquid fermentation of fungus Pleurotus ostreatus was established.

Methodology: Treatment of tetrachloro-auric acid (HAuCl4) solution with the free cell filtrate (FCF) of the fungus led to the reduction of the HAuCl4 ions and the formation of stable GNPs. These nanoparticles were characterized by Surface Plasmon Resonance (SPR) band at wavelength 550 nm for GNPs. The components of the media needed for the fungal growth were optimized using factorial design.

Results: The maximum SPR in UV-Vis spectra was recorded using a medium containing in (%); glucose (1), yeast (0.5), malt extract (0.5) and KNO3 (0.2) and incubation period 8 days, the temperature and pH were kept at 30°C and 6, respectively. The particles were characterized by UV/Vis spectroscopy, Transmission electron microscope (TEM), Dynamic light scattering (DLS), Fourier Transform and Infrared Spectroscopy (FT-IR). Exposure of fungal strain or FCF after mixing with Au+ to Gamma radiation showed 36% increase in the SPR band intensity of the synthesized GNPs compared to un-irradiated strain and FCF irradiated before mixing with Au+. The synthesized GNPs exhibited antimicrobial activity against both Gram negative and Gram positive bacteria, measured by well diffusion assay. Moreover, it also showed good anticancer activity against human Breast carcinoma (T47D) cells, Prostate carcinoma (PC3) cells and hepatocellular (HEPG2) cells using Trypan blue exclusion and Sulfo-Rhodamine B assay.

Conclusion: The combined effect of both ɤ-radiation and proteins offers a highly efficient and inexpensive method for the synthesis of gold nanoparticles utilizing an edible mushroom, P. ostreatus for the bio- reduction of HAuCl4.