Characterization, antioxidant property and cytoprotection of exopolysaccharide-capped elemental selenium particles synthesized by Bacillus paralicheniformis SR14

Instead of using existing methods to chemically synthesize elemental selenium particles (CheSePs), which first require separating and purifying polysaccharides or proteins and adding extra reducing agent, this study applied a novel method to directly assemble exopolysaccharide-capped biogenic elemental selenium particles (EPS-BioSePs) by Bacillus paralicheniformis SR14 during the metabolic process. Characterization by energy dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), size measurement and chemical composition analysis verified that EPS-BioSePs exhibited a monodispersed and homogeneous spherical structure 293.73 +/- 4.03 nm in size. Compared to a widely used form of CheSePs stabilized and coated by bovine serum albumin, EPS-BioSePs exhibited better antioxidant properties on scavenging DPPH, superoxide and ABTS free radicals, but not hydroxyl radical. In vitro experiments with porcine jejunum epithelial (IPEC-J2) cells also indicated a significant cytoprotection of EPS-BioSePs against hydrogen peroxide-induced oxidative stress, as exhibited by cell viability reduction and suppression of ROS generation. These results suggested that this new form of selenium possessed great antioxidant property and cytoprotection and exopolysaccharide-producing bacteria could gradually become an appropriate choice to synthesize biogenic elemental selenium particles with potential applications as antioxidants.