Oxidation-engineered in soy protein-oxidized alginate in situ hydrogels: The evolution from "point-point" to...

In this study, a novel environmentally friendly in situ hydrogel was developed using soy protein isolate (SPI) and oxidized sodium alginate (OSA), which were directly cross-linked via dynamic Schiff base bonds. The results indicated that the tightly ordered network structure between SPI and OSA could be formed through the orientation and arrangement of molecular chains, relying on Schiff base covalent bonds and non-covalent interactions. SEM observations revealed that the cross-linking between networks evolved from a "linear structure" to a "planar structure" as the oxidation degree increased, and the cross-linked regions continued to thicken. FTIR and XPS analyses demonstrated that moderate oxidation enhanced the covalent interactions of Schiff bases, while the non-covalent interactions were also strengthened, thereby facilitating the stable construction of the gel network structure. Interestingly, GSPI-OSA-4 (SA:NaIO₄ = 5:4, w/w) was shown to possess the best stability and water holding capacity, along with the lowest swelling characteristics. At this point, the gel exhibited the highest support and mechanical properties, and was integrated into the network, showing the strongest resistance to deformation. The purpose of this study was to provide theoretical support and potential applications for the development of environmentally friendly hydrogels.