Synthesis and properties of selenium nanoparticles in natural polysaccharides 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, were characterized by maximum absorption at 256 nm. The process of formation and morphological characteristics of them were studied at different mass ratio of the components in the selenium-polysaccharide complex (in the range from 0.01 to 0.10). The morphological, dimensional, and spectral characteristics of obtained selenium nanoparticles were determined by transmission electron microscopy (TEM) and UV spectroscopy. The sample of nanoselenium was shown to consist of single nanoparticles, mostly spherical or partially elongated shapes, with an average size of 40 nm. The replacement of alginate (no more than 10%) with chitosan causes a significant increase in the stability of selenium nanoparticles, preventing them against 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. On contrary, sodium selenite, used for a comparison, decreased the bioluminescence of A. fischeri F1 at concentrations more than 100 mg/L. The values of NA2SeO3 half maximal effective concentration (EC50) were measured to be 420-820 mg/L at 15-60 minutes of incubation. Chronic biotoxicity of sodium selenite was manifested at concentrations more than 30 mg/L, and at 300 mg/L and higher led to a complete suppression of A. fischeri F1 growth and bioluminescence. Experimental study of biological properties of obtained selenium nanoparticles revealed an increase in seed germination and vigor of pea (Pisum sativum L.) of Madonna variety and barley (Hordeum vulgare L.) of Kuzen variety, as well as an increase in the dry matter mass of their roots and aerial parts. A high activity of growth processes for the studied crops was noted at a nanoselenium concentration of 20 mg/l.