Antioxidant activity of selenium nanoparticles biosynthesized using a cell-free extract of Geobacillus

Abstract

Selenium is a nutrient element essential for the growth and reproduction of plants and animals. Generally, selenium nanoparticle has a high level of absorption in regular supplementation comparative to selenium. In this study, selenium nanoparticles have been synthesized using a cell-free extract of Geobacillus as a reducing and stabilizing agent. This is for the first time; Geobacillus has been used for the synthesis of selenium nanoparticles. The cell-free extract of bacteria has active enzymes that are responsible for the reduction of sodium selenite to prepare selenium nanoparticles. The cell-free extract increased the reduction process comparative to the bacterial reduction. The biosynthesized nanoparticles were characterized by UV-visible spectrophotometry, transmission electron microscopy along with selected area electron diffraction, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy. The spherical nanoparticles have diameters in the range of 30 to 60 nm. The antioxidant activity was evaluated by various antioxidant assays. This study revealed that biofunctionalized selenium nanoparticle has more antioxidant activity than sodium selenite and cell-free extract. Abbreviations: ABTS: 2,2’-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid); DPPH: 1,1-diphenyl-2-picrylhydrazyl; EDTA: ethylenediaminetetraacetic acid; EDAX: energy dispersive X-ray analysis; FRAP: ferric reducing antioxidant power; FTIR: Fourier transform infrared spectroscopy; PBS: phosphate buffered saline; PMSF: phenylmethylsulfonyl fluoride; SAED: selected area electron diffraction; SeNP: selenium nanoparticles; TEM: transmission electron microscopy; TPTZ- 2,4,6-Tri(2-pyridyl)-s-triazine; YAG: yttrium aluminium garnet