Preparation and Characterization of pH-Responsive Fucoidan/Carboxymethyl Chitosan Hydrogel Beads for Curcumin Encapsulation and in vitro Gastrointestinal Release

Abstract

The hydrogel beads were developed through physical crosslinking between fucoidan, carboxymethyl chitosan, and the encapsulated bioactive compound curcumin.Structural characterization confirmed that intermolecular hydrogen bonding between fucoidan and carboxymethyl chitosan plays a pivotal role in the hydrogel network formation. Curcumin was efficiently encapsulated within the hydrogel beads, functioning as an additional crosslinking agent that increased crosslinking density and reduced equilibrium water content of the system. Notably, the hydrogel beads protected curcumin via non-covalent interactions and physical barriers, enhancing its thermal and UV stabilities. Furthermore, the hydrogel beads exhibited pronounced pH-responsive swelling and release behaviors, showing minimal swelling and limited release in acidic gastric conditions, in contrast to sharp swelling and near-complete release in alkaline intestinal environments, attributed to the pH-dependent protonation states of polysaccharides functional groups altering intermolecular interactions. Importantly, the encapsulated curcumin retained more than 90% antioxidant capacity following simulated gastrointestinal digestion. This platform is promising for bioactive compounds controlled delivery with great potential in nutraceuticals and functional foods.