High-amylose maize starch-containing hydrogel beads for integrating curcumin-loaded natural deep eutectic solvent:...

Curcumin is a hydrophobic bioactive compound with limited oral applicability due to its poor water solubility and low stability. In this study, high-amylose maize starch (HAMS)-containing hydrogel beads were developed for the encapsulation of curcumin-loaded natural deep eutectic solvent (CLDES). Sodium alginate (SA) formed an ionically crosslinked hydrogel matrix through Ca²⁺-induced gelation, while HAMS contributed to additional physical associations within the hydrogel system. The hydrogel beads showed HAMS-content-dependent differences in their structural properties. The average bead diameter increased from 2.41 ± 0.02 mm (H0) to 3.14 ± 0.02 mm (H25). SEM showed a progressively denser internal structure with increasing HAMS content. LF-NMR analysis revealed differences in water mobility and distribution among formulations with different HAMS contents. In addition, the maximum thermal degradation temperature increased from 248.3 °C (H0) to 313.7 °C (H35), indicating formulation-dependent differences in thermal degradation behavior at higher HAMS levels. The swelling ratio and water holding capacity decreased with increasing HAMS content, while the loading capacity gradually stabilized at higher HAMS levels. Under simplified simulated gastrointestinal conditions, all hydrogel beads exhibited limited curcumin release in simulated gastric fluid (below 3% within 2 h), followed by markedly increased release in simulated intestinal fluid. Release kinetic analysis suggested that the release behavior was associated with combined effects of network relaxation, swelling, and structural disintegration rather than simple Fickian diffusion. Overall, the HAMS-containing CLDES hydrogel beads developed in this study provide a facile strategy for the encapsulation and controlled release of hydrophobic bioactive compounds.