Gut microbiota mediated immunoregulatory effects of Dendrobium officinale polysaccharides-selenium nanoparticles complexes

Dendrobium officinale polysaccharides (DOP), as a natural active ingredient, has exhibited strong immunomodulatory and antioxidant effects. Selenium nanoparticles (SeNPs) also possess various biological activities, but the unstable properties limit their applications. This research focused on modification of SeNPs by DOP to form stable complexes (DOP-SeNPs), and the analysis of structural characterization and gut microbiota-mediated immune regulation mechanisms. The results showed that DOP-SeNPs were prepared through hydrogen bond interaction and presented uniform particle size distribution (average particle size of about 100 nm) and good stability. Animal experiments demonstrated that DOP-SeNPs significantly protected the immune organs in cyclophosphamide-induced immune injury mice. Besides, DOP-SeNPs effectively regulated the gut microbiota diversity including promoting the enrichments of probiotics such as Lactobacillus and Lachnospiraceae NK4Al36 group compared with model group, and improved the lymphocyte subsets proportions through the regulation of metabolic pathways including biosynthesis of various antibiotics, protein digestion and absorption, chemical carcinogenesis-DNA adducts. In conclusion, DOP-SeNPs presented stable structure characteristics and improved the immune functions of immune-injured mice by influencing the gut microbiota metabolism. These results will provide a certain theoretical basis and data support for the applications of DOP and the nano-selenium complex in functional food industry.