Lignocellulose processing-induced pH-responsive Pickering emulsions for curcumin delivery

The development of pH-responsive Pickering emulsions is of critical importance for delivery systems that do not involve synthetic ligands or chemical modifications, which helps to preserve the preservation of biomaterial safety. Lignocellulose derived colloidal particles (LCPs) with in-situ generated carboxyl groups were prepared from bougainvillea spectabilis stems via an acid/alkali biorefining process. The obtained LCPs exhibited pH-responsive emulsifying behavior, stabilizing high-internal-phase Pickering emulsions (HIPPEs) under alkaline conditions and undergoing controlled demulsification under acidic conditions. The emulsion system showed reversible pH-responsiveness, maintaining over 95% stability after at least eight cycles of emulsification/demulsification. For curcumin delivery, the encapsulation efficiency reached 92.5%. The in vitro release profiles showed faster release in simulated gastric fluid (Higuchi constant K_H = 29.2) and sustained release in simulated intestinal fluid (K_H = 18.5). The bioaccessibility of curcumin was enhanced from 8.52% to 43.08%, representing a 5.11-fold improvement. Furthermore, it promoted lipid hydrolysis with an efficiency of 57.22%, which was 7.15 times higher than that of pure sunflower oil. Cytotoxicity tests indicated biocompatibility, with cell viability exceeding 90% even at LCPs concentrations of up to 1000 μg/mL. Collectively, a biorefining pathway is established, transforming underutilized plant resources into a colloidal platform with processing-induced pH-responsiveness for targeted nutrient delivery.