pH-responsive dual-layered chitosan/Tween 80 nanoemulsions for gastrointestinal targeted delivery of curcumin

Curcumin's application is severely hindered by its hydrophobicity, poor solubility and rapid degradation. This study developed a pH-responsive, dual-layered curcumin-chitosan nanoemulsion (nCCURs) system using the phase inversion temperature method coupled with probe ultrasonication. The platform comprises a curcumin-loaded coconut oil core, a Tween 80 interlayer and a cationic chitosan shell. The optimized nCCURs exhibited an ultra-fine mean particle size of 26.9 nm, a narrow polydispersity index of 0.26 and a robust zeta potential of +34.4 mV. Transmission electron microscopy confirmed their spherical, dual-layered core-shell architecture. Biologically, nCCURs demonstrated powerful 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity (IC50 ∼72 µg ml–1) and significant antibacterial efficacy against Escherichia coli (25.5 mm inhibition zone). In vitro gastrointestinal digestion profiles revealed targeted, pH-responsive release, with only 16.5% curcumin leaked in the gastric phase (pH 2.0) versus 85.5% in the intestinal phase (pH 6.4). Kinetic modelling elucidated a structural transition from anomalous transport in gastric fluid to Fickian diffusion in intestinal fluid, driven by pH-triggered erosion of the chitosan shell. These findings highlight nCCURs as a high-performance oral delivery platform for hydrophobic nutraceuticals.