Synergistic enhancement of curcumin bioaccessibility via pH-responsive sanxan-chitosan core-shell hydrogel beads: a strategic formulation for intestinal-targeted delivery

Curcumin (Cur) suffers from poor aqueous solubility and low bioaccessibility, limiting its practical applications. In this study, pH-responsive core-shell hydrogel beads were developed using sanxan (SAN) and chitosan (CS) to improve Cur stability and gastrointestinal delivery. SAN served as the loading matrix, while CS provided an outer protective shell. The optimized Cur-SAN@CS beads showed a high apparent encapsulation efficiency (99.80%), improved photostability, and enhanced thermal stability. No detectable Cur release was observed in simulated gastric fluid, whereas sustained release occurred in simulated intestinal fluid, resulting in bioaccessibility above 82%. The release data in the main intestinal stage were best fitted by the Higuchi model, although the overall release behavior likely involved diffusion together with matrix swelling and partial erosion. These results indicate that SAN-CS core-shell hydrogel beads are a useful natural polymer-based delivery system for improving the stability and in vitro bioaccessibility of hydrophobic bioactives.