In this study, zein nanoparticles coated with carboxymethyl chitosan (CMCS) were prepared to encapsulate vitamin D3 (VD3). VD3 was first encapsulated into zein nanoparticles using a low-energy phase separation method and coated with CMCS simultaneously. Then, calcium was added to cross-link CMCS to achieve thicker and denser coatings. The nanoparticles with CMCS coatings had a spherical structure with particle size from 86 to 200 nm. The encapsulation efficiency was greatly improved to 87.9% after CMCS coating, compared with 52.2% for that using zein as a single encapsulant. The physicochemical properties were characterized by differential scanning calorimetry and Fourier transform infrared spectroscopy. Nanoparticles with coatings provided better controlled release of VD3 in both PBS medium and simulated gastrointestinal tract. Photostability against UV light was significantly improved after encapsulation. Encapsulation of hydrophobic nutrients in zein nanoparticles with CMCS coatings is a promising approach to enhance chemical stability and controlled release property.

Nanoparticles were synthesized from soy protein, one of the most abundant and widely utilized plant proteins, for nutraceutical and drug encapsulation. The preparation process consisted of dispersion, desolvation, drug incorporation, cross-linking, and evaporation. The role of each procedure in the formation of nanoparticles was systematically investigated by means of particle size, size distribution, and zeta potential as well as morphology observation. Curcumin as a model drug was encapsulated successfully into the nanoparticles, evidenced by Fourier transform infrared spectroscopy and X-ray diffraction patterns. The average size of the curcumin-loaded nanoparticles was 220.1 to 286.7 nm, and their zeta potential was around -36 mV. The highest encapsulation efficiency and loading efficiency achieved were 97.2% and 2.7%, respectively. The release of curcumin in phosphate buffer saline followed a biphasic pattern. Possible mechanisms of the formation of soy protein nanoparticles as well as the incorporation of curcumin were discussed based on the data obtained from this study.

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Cellular evaluation of zein nanoparticles has not been studied systematically due to their poor redispersibility. Caseinate (CAS)-stabilized zein nanoparticles have been recently developed with better redispersibility in salt solutions. In this study, zein-CAS nanoparticles were prepared with different zein/CAS mass ratios. The prepared nanoparticles demonstrated good stabilities to maintain particle size (120-140 nm) in cell culture medium and HBSS buffer at 37 °C. The nanoparticles showed no cytotoxicity for Caco-2 cells for 72 h. CAS not only significantly enhanced cell uptake of zein nanoparticles in a concentration- and time-dependent manner but also remarkably improved epithelial transport through Caco-2 cell monolayer. The cell uptake of zein-CAS nanoparticles indicated an energy-dependent endocytosis process as evidenced by cell uptake under blocking conditions, that is, 4 °C, sodium azide, and colchicine. Fluorescent microscopy clearly showed the internalization of zein-CAS nanoparticles. This study may shed some light on the cellular evaluations of hydrophobic protein nanoparticles.