Synthesis, Characterization, and Stability Study of Selenium Nanoparticles Coated with Purified Polysaccharides from <i>Ononis natrix</i>

Selenium nanoparticles (SeNPs) attract considerable attention for their promising applications in the biomedical field, driven by their unique properties and antioxidant activities. However, their practical use is often hindered by issues such as instability and aggregation. In this study, a polysaccharide, P2, extracted from Ononis natrix, was used to stabilize SeNPs to address these limitations. P2-SeNPs were prepared through a green synthesis method involving sodium selenite, P2, and ascorbic acid, and characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). P2-SeNPs exhibited a smaller particle size and enhanced stability compared to unmodified SeNPs. UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS) demonstrated the presence of Se-O bonds, suggesting effective stabilization by covalent bonding between SeNPs and P2. Stability tests revealed that P2-SeNPs maintained good dispersion under various conditions, with optimal stability observed at refrigerated temperatures and neutral pH. Moreover, P2-SeNPs exhibited better antioxidant activities than unmodified SeNPs, as evidenced by higher DPPH radical scavenging, ABTS radical scavenging, and metal chelation ratios. This difference is attributed to both the reduced aggregation and smaller size of P2-SeNPs. Therefore, it is concluded that P2-SeNPs exhibit significant potential as an effective antioxidant agent for biomedical applications.