Synthesis and Properties of Selenium Nanoparticles in a Natural Polysaccharide Matrix

Selenium nanoparticles were obtained by reduction of sodium selenite in aqueous solutions of nonstoichiometric alginate-chitosan polyelectrolyte complexes. Amorphous red nanosized selenium, formed as a result of the reaction, was characterized by a maximum absorption at 256 nm. The process of formation and morphological characteristics of the nanoparticles were studied at different mass ratios of the components in the selenium-polysaccharide complex (in the range from 0.01 to 0.10). The morphological, dimensional, and spectral characteristics of the obtained selenium nanoparticles were determined by transmission electron microscopy (TEM) and UV spectroscopy. The sample of nanoselenium was shown to consist of single nanoparticles having mostly spherical and, to a lesser extent elongated, shape, with an average size of similar to 40 nm. Replacement of alginate (<= 10%) with chitosan caused significant increase in stability of the selenium nanoparticles, preventing their aggregation and color change for three months. The biotoxicity of the synthesized nanoselenium was studied using Aliivibrio fischeri F1 bioluminescent assay. Selenium nanosamples were found to have no any inhibitory effect on bacterial bioluminescence and growth and thus have neither acute nor chronic biotoxicity. Sodium selenite used for comparison, on the contrary, decreased the bioluminescence intensity of A. fischeri F1 at concentrations greater than 100 mg/L. The half maximal effective concentrations (EC50) of Na2SeO3 were measured to be 420-820 mg/L at 15-60 min of incubation. Chronic biotoxicity of sodium selenite was manifested at concentrations greater than 30, and 300 mg/L and higher concentrations led to complete suppression of A. fischeri F1 growth and bioluminescence. Experimental study of the biological properties of the obtained selenium nanoparticles revealed increases in the seed germination and vigor of Madonna variety of pea (Pisum sativum L.) and of Kuzen variety of barley (Hordeum vulgare L.), as well as an increase in the dry matter mass of their roots and aerial parts. A high activity of the growth processes for the studied crops was noted at a nanoselenium concentration of 20 mg/L.