Harnessing selenium nanoparticles (SeNPs) for enhancing growth and germination, and mitigating oxidative stress in Pisum sativum L.

Selenium, an essential micronutrient for plants and animals, can cause selenium toxicity as an oxyanion or at elevated doses. However, the toxic selenite (SeO32-) oxyanion, can be converted into less harmful elemental nano-selenium (Se0), with various practical applications. This research aimed to investigate two methods for reducing SeO32-: abiotic reduction using cell-free extract from Enterococcus spp. (abiotic-SeNPs) and chemical reduction involving L-ascorbic acid (chemical-SeNPs). Analysis with XPS confirmed the presence of Se0, while FTIR analysis identified surface functional groups on all SeNPs. The study evaluated the effects of SeO32-, abiotic-SeNPs, and chemical-SeNPs at different concentrations on the growth and germination of Pisum sativum L. seeds. SeO32- demonstrated detrimental effects on germination at concentrations of 1 ppm (germination index (GI) = 0.3). Conversely, both abiotic- and chemical-SeNPs had positive impacts on germination, with GI > 120 at 10 ppm. Through the DPPH assay, it was discovered that SeNPs exhibited superior antioxidant capabilities at 80 ppm, achieving over 70% inhibition, compared to SeO32- (less than 20% inhibition), therefore evidencing significant antioxidant properties. This demonstrates that SeNPs have the potential to be utilized as an agricultural fertilizer additive, benefiting seedling germination and development, while also protecting against oxidative stress.

Enterococcus spp. Cell-Free Extract: An Abiotic Route for Synthesis of Selenium Nanoparticles (SeNPs), Their Characterisation and Inhibition of Escherichia coli.

Selenite (SeO32-), the most toxic and most reactive selenium (Se) oxyanion, can be reduced to elemental selenium (Se0) nanoparticles by a variety of bacteria, including Enterococcus spp. Previously, the orthodox view held that the reduction of SeO32- to Se0 by a wide range of bacteria was solely accomplished by biological processes; however, recent studies have shown that various bacterial strains secrete metal-reducing metabolites, thereby indirectly catalysing the reduction of these metal species. In the current study, selenium nanoparticles were synthesised from the abiotic reduction of selenite with the use of Enterococcus spp. cell-free extract. Once separated from the cell-free extract, the particles were analysed using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Transmission electron microscopy (TEM) and a Zetasizer. The results revealed that the SeNPs were spherical in shape, containing both amorphous and crystalline properties, and the sizes with the highest frequency ranged close to 200 nm. Additionally, the obtained nanoparticles exhibited antimicrobial properties by directly inhibiting the viability of an E. coli bacterial strain. The results demonstrate not only the potential of abiotic production of SeNPs, but also the potential for these particles as microbial inhibitors in medical or similar fields.