Fabrication of curcumin−loaded foxtail millet prolamin−based nanoparticle: Impact of curdlan sulfate on the particle properties

The sulfation of curdlan was achieved by modification of curdlan with sulfur trioxide–pyridine complex. Curcumin−loaded curdlan sulfate−sodium caseinate stabilized foxtail millet prolamin nanoparticles were fabricated using pH-driven method. Under the optimal conditions, two kinds of foxtail millet prolamin−based nanoparticles were fabricated using different preparation processes for the first time. The mean diameters and zeta-potentials of co−assembled foxtail millet prolamin−sodium caseinate−curdlan sulfate nanoparticles and curdlan sulfate coated co−assembled foxtail millet prolamin−sodium caseinate nanoparticles were 84.7 nm, 136.4 nm and − 45.7 mV, − 41.5, respectively. Molecular docking and infrared spectroscopy indicated that the curcumin was retained in the hydrophobic region of foxtail millet prolamin though four hydrogen bonds and ten hydrophobic interactions, and amino residues of proline, arginase, cysteine, glycine, and alanine served as the main binding sites for curcumin. The deposition and co−assembly of curdlan sulfate enhanced the curcumin encapsulation efficiency from 78.3% to 81.8% and 85.9%, respectively, and slightly reduced the release of curcumin under physiological and endosomal pH conditions. Consequently, the intake of curdlan sulfate−sodium caseinate stabilized composite nanoparticles encapsulated−curcumin by MCF-7 cells was lower than that of sodium caseinate stabilized nanoparticles entrapped−curcumin, and increased the IC50 value from 5.3 μg/mL to 10.5 and 9.0 μg/mL, respectively. This study showed that the biopolymeric nanoparticles have the potential to encapsulate hydrophobic bioactives, and the incorporation of curdlan sulfate exhibited a significant effect on the physicochemical properties, encapsulation, and release profile of foxtail millet prolamin particles.