Hydroxypropyl methylcellulose enhances locust bean gum-mucin interactions: Implications for curcumin migration in mucus

Our previous study has shown that the locust bean gum (LBG) and hydroxypropyl methylcellulose (HPMC) complexes (LHs) can load 55 wt% curcumin, approximately double that of conventional food-based vehicles. This study found that HPMC enhanced the three-stage interactions between LBG and mucin, thereby regulating the ex vivo migration behavior of amorphous curcumin in the mucus. Analyses of the contact, diffusion, and entanglement stages of the interactions with mucin showed that LBG, HPMC, and LHs all interacted with mucin. Hydrogen bonds and hydrophobic interactions were key to mucin-LHs binding, dominated by hydrophobic effects. In LHs, LBG dominated the interaction with mucin, while HPMC modulated the interaction strength. After being combined with HPMC, the flexibility of the LBG molecular chain increased, exposing more interaction sites, which enhanced the affinity between LHs and mucin, optimized the diffusion process, and promoted the entanglement between LHs and mucin. The strongest interactions between LH3-2 and mucin triggered local aggregation and contraction of mucin, and/or enabled the sample to adhere better, increasing the cumulative release of curcumin and thus improving the ex vivo migration behavior of curcumin within the simulated mucus layer. This work constitutes a systematic progression aimed at developing a high-bioavailability delivery system based on an established high-loading platform and establishes a foundation for modeling carrier-drug loading efficiency, mucosal permeability, and bioutilization relationships.