Anti-Aging Potential of Biogenic Selenium Nanoparticles and Selenium/Polysaccharides Nanoconjugate Biosynthesized by Bacillus subtilis Isolated from Selenium-Rich Soil

Selenium nanoparticles (SeNPs), which are nanoscale particles of elemental selenium (Se 0 ), combine the biological activity of selenium with the distinctive properties inherent in nanomaterials, thereby making SeNPs a more promising candidate for advancing selenium-based resources. In this work, several strains of Bacillus with sodium selenite-reducing ability were isolated from selenium-rich soils. Bacillus subtilis ESNS-2 with high selenium tolerance was selected as the target strain. Under culture conditions supplemented with 5 mmol/L sodium selenite, this strain exhibited a reduction efficiency of 75.4 ± 0.6% over 24 h. The produced bioSeNPs were purified, decorated using polysaccharides from the seeds of Plantago asiatica L. (PLP), and subsequently systematically characterized using various means. The results revealed that the prepared PLP-bioSeNPs were regularly spherical elemental selenium particles, with an average particle size of 96.9 ± 1.1 nm, a PDI of 0.108 ± 0.003, and a zeta potential of −19.7 ± 0.4 mV. Characterization confirmed that they exhibited excellent dispersibility and stability. In vitro antioxidant assays, both bioSeNPs and the PLP-bioSeNP complex demonstrated pronounced dose-dependent scavenging activity against DPPH• and ABTS + • radicals. In a D-galactose-induced aging mouse model, both bioSeNPs and PLP-bioSeNPs alleviated D-galactose-induced hepatic and cerebral damage, as well as associated behavioral deficits, through the modulation of oxidative stress balance and suppression of inflammation. This study successfully accomplished the efficient production of SeNPs utilizing Bacillus subtilis ESNS-2. The modification of PLP provided innovative strategies for the development of macromolecular drugs, with a specific emphasis on enhancing stability.