Abstract: Hydrogel is a kind of hydrophilic substance with a three-dimensional network structure, which has the potential to deliver active substances and load probiotics. Chitosan (CS) and sodium Hyaluronate (SH) were mixed 1:1 (v:v) as raw materials. A physically crosslinked hydrogel was constructed by electrostatic interaction, and its mechanical properties, microstructure, and functional properties were characterized. At the same time, the hydrogel was used as the carrier to load probiotics, and the influence of probiotics on the mechanical properties and microstructure characterization of hydrogels was clarified. The bacteria-carrying properties were analyzed, and the release mechanism of probiotic hydrogels in the simulated gastroenteric fluid was explored. The results showed that CS-SH hydrogel had good mechanical properties and bacteria-carrying properties through hydrogen bond crosslinking, and the loading capacity of LR and PA can reached 1.15×109 cfu and 1.25×109 cfu. In the gastrointestinal digestion simulation, the probiotic hydrogel group was continuously released in intestinal fluid, and its release mechanism was surface erosion release. The maximum total number of colonies in the intestinal fluid was 6.30 log(cfu/mL) and 6.12 log(cfu/mL), respectively. CS-SH hydrogel could be crosslinked by electrostatic interaction, and could be continuously released in intestinal fluid, which was a potential delivery carrier. This study provided theoretical guidance and a research basis for the application and mechanism of physically crosslinked hydrogels in the field of loaded probiotics.

Key words: Physically cross-linked hydrogels, Chitosan, Sodium hyaluronate, Bacteria-carrying performance, Gastrointestinal digestive simulation