Lycium barbarum Polysaccharide Stabilized Selenium Nanoparticles Exhibit Antibacterial Activity and Ameliorate Escherichia coli-Induced Diarrhea in Mice

Lycium barbarum polysaccharides are major bioactive constituents of Lycium barbarum fruit and are widely recognized for antioxidant, immunomodulatory, and intestinal protective activities. Selenium nanoparticles are considered a safer selenium formulation than conventional inorganic selenium because they generally provide improved bioavailability and reduced toxicity. In this study, Lycium barbarum polysaccharide-stabilized selenium nanoparticles were prepared under mild conditions, characterized, and evaluated for antibacterial, antibiofilm, and antidiarrhoeal activities. The optimized nanoparticles exhibited a hydrodynamic diameter of 304.4 ± 32.9 nm, a polydispersity index of 0.369 ± 0.05, and a zeta potential of −20.8 ± 1.5 mV, indicating good colloidal stability. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy supported the structural assignment of spherical elemental selenium particles with a polysaccharide-rich surface layer. In vitro assays showed concentration-dependent inhibition of Escherichia coli, with minimum inhibitory and minimum bactericidal concentrations of 100 and 200 μg Se/mL, respectively. Biofilm formation was also markedly reduced, and scanning electron microscopy demonstrated severe bacterial surface damage after treatment. In a KM mouse model of Escherichia coli-induced diarrhea, oral administration of the nanoparticles significantly lowered diarrhea scores, improved body weight recovery, and alleviated intestinal mucosal injury compared with untreated infected mice. Major organs showed no obvious histopathological abnormalities under the experimental conditions. Overall, these findings identify Lycium barbarum polysaccharide-stabilized selenium nanoparticles as a promising selenium-based nanomaterial for controlling bacterial diarrhea and protecting intestinal health. These results provide a practical foundation for future mechanistic, pharmacokinetic, microbiological, and translational studies aimed at broader intestinal applications.