Physicochemical properties and bioavailability comparison of two quercetin loading zein nanoparticles with outer shell of caseinate and chitosan

Two quercetin loading zein nanoparticles with shell of caseinate (SC-ZNP) and caseinate-chitosan double layer (CHC-ZNP) were fabricated by anti-solvent method. The formulas of the two nanoparticles were optimized and their physicochemical properties and bioavailability enhancement effect were compared in both in vitro and in vivo. The particle size, zeta potential, encapsulation efficiency and loading efficiency of SC-ZNP were 188 nm, −29.33 mV, 82.78% and 1.58%, while these values for CHC-ZNP were 551 nm, + 57.47 mV, 78.26% and 2.91%, respectively. Physicochemical characterization showed that quercetin lost its crystalline structure and existed in amorphous form in both nanoparticles. After freeze-drying, SC-ZNP showed better redispersibility and smaller size change than CHC-ZNP. Both nanoparticles significantly improved the solubility and passive diffusion velocity of quercetin. The coating of caseinate shell provided better colloidal stability (pH, salt and storage) than caseinate-chitosan double layers. Both SC-ZNP and CHC-ZNP exhibited mucoadhesive properties and significantly decreased the feces excretion of quercetin in rat. Because of smaller particle size, SC-ZNP penetrated into the mucous layer more easily. After oral administration, few free quercetin was found in rat plasma, while many metabolites were detected. Through semi-quantification of its most dominant metabolite, the bioavailability of quercetin in SC-ZNP and CHC-ZNP groups were 2.34 and 1.89 times enhanced.