A double-network hydrogel based on marine polysaccharides for promoting enamel remineralization

Enamel demineralization is the most common complication associated with orthodontic treatment, and current therapeutic strategies remain limited. If the lesions are not treated in time, dental caries are likely to be induced by cariogenic oral bacteria. Amorphous calcium phosphate (ACP) plays a crucial role in remineralization as the biomineralization precursor, but it is hard to work with independently. An ACP-releasing hydrogel exhibiting wet adhesion and rapid remineralization capabilities is urgently needed. Based on the excellent biocompatibility of marine polysaccharides, oxidized sodium alginate (OSA) with aldehyde groups was synthesized in the alcohol-water phase through a sodium periodate-mediated reaction. It could self-crosslink with amino groups of carboxymethyl chitosan (CMCTS) and dopamine (DA) to form dynamic imine bonds, preparing an in-situ injectable hydrogel (SDC, DA-modified sodium alginate carboxymethyl chitosan hydrogel). ACP was subsequently incorporated to achieve secondary cross-linking mediated by calcium ions, thereby constructing a dense double-network composite hydrogel (SDC-ACP, DA-modified sodium alginate carboxymethyl chitosan hydrogel loaded with ACP). Its physicochemical, antibacterial, biological, and remineralization properties were characterized. The results demonstrated that the in situ hydrogel exhibited an interconnected three-dimensional porous architecture with stable mechanical properties, and ACP was uniformly distributed in the form of nanospheres. DA incorporation improved the adhesion ability of the hydrogel and imparted moderate antibacterial and anti-biofilm activities against Streptococcus mutans ( S.mutans ). The composite hydrogel exhibited good biocompatibility with L929 cells and human gingival fibroblasts. Notably, it significantly promoted remineralization of demineralized enamel within 7 days, and the hardness of treated enamel was close to that of healthy enamel after 14 days of treatment. Overall, this composite hydrogel provides a potential strategy for enamel remineralization.