Effects of colloidal delivery systems for curcumin-Brassica rapa L. polysaccharide mixture encapsulation on physicochemical properties, stability, and gut microbiota modulation.

The therapeutic potential of curcumin is severely constrained by its poor physicochemical stability and low oral bioavailability. Co-formulation with Brassica rapa L. polysaccharide offers a promising strategy to enhance its functionality; however, the impact of different colloidal delivery systems on the encapsulation performance and subsequent biological fate of this mixture remains unclear. In this study, we systematically compared three spray-dried delivery platforms, including liposomes (LP-CP), sodium caseinate nanoparticles (SC-CP), and β-cyclodextrin inclusion complexes (CYC-CP), for encapsulating CP. Our results demonstrated that the carrier system critically determined encapsulation performance, with SC-CP exhibiting superior curcumin loading capacity (7.24%), curcumin thermal stability (82.87% retention at 95 °C), and favorable hygroscopicity profiles. Notably, SC-CP facilitated enhanced colonic accumulation in vivo, achieving a peak accumulation of 53.45% at 8 h post-gavage, representing a 15-fold increase compared to curcumin from unencapsulated CP. By integrating in vitro fermentation models with in vivo animal experiments and employing 16S rRNA sequencing alongside short-chain fatty acid (SCFA) analysis, we systematically elucidated the carrier-specific modulatory effects on the gut microbiota. In the in vitro fermentation system, SC-CP significantly promoted the production of acetate, propionate, and butyrate, while enriching butyrate-producing genera such as Lachnospiraceae_NK4A136_group. In the in vivo animal model, SC-CP intervention resulted in a 1.6-fold increase in cecal butyrate levels and a marked increase in the abundance of beneficial genera, including Akkermansia, demonstrating superior modulation of microbial community structure and metabolic function. Collectively, these findings establish that the selection of a colloidal carrier not only dictates the physicochemical stability of the curcumin-polysaccharide mixture but also governs its spatiotemporal distribution within the gastrointestinal tract and its prebiotic capacity to remodel the gut microecology. This study provides a theoretical foundation for the rational selection of delivery systems to maximize the functional efficacy of bioactive ingredients in functional food applications.