Preparation and properties of zein-chitosan nano-nutrient delivery particles

Low oral bioavailability has posed a great challenge on some active substances such as curcumin (Cur) in functional food. Therefore, it is highly demanding for the high water solubility, chemical stabilities, absorption rate, but low metabolic rate in the active substances for the high-quality development of food industries. Currently, the protein and polysaccharide can be expected to construct nano-nutrient delivery, where the complex particles with the diameter of 100-1 000 nm can be considered as an important way to improve the stability and utilization of food-active substances. Zein can also be used to form nano-size spherical particles, thereby embedding into the active substances during antisolvent precipitation in the polar solvent. However, zein nanoparticle is prone to aggregation and precipitation in the dispersion solution. Alternatively, polysaccharides can serve as stabilizers in the preparation of zein nanoparticles. In this study, chitosan with different molecular weights was complexed with zein to fabricate zein-chitosan nanoparticles, in order to achieve the delayed-release capability by the anti-solvent precipitation. An investigation was also made on the effects of chitosan molecular weight (LC: 5×104 Da, MC: 1×105 Da, HC: 3.4×105 Da), while the mass ratio of zein and chitosan (2:1, 4:1, 6:1, 8:1, 10:1) on the particle distribution, zeta potential, the loading Cur performance of zein-chitosan nanoparticles. SEM and FT-IR were selected to characterize the microstructure, morphology, and phase composition, further to elucidate the formation mechanism of composite nanoparticles. Moreover, the slow-release performance and the stability of Cur-loaded composite nanoparticles were evaluated at different pH, ionic strengths, and storage time. The results showed that the Cur-loaded composite nanoparticles presented the smaller particle size of 80.13 nm with a high zeta potential of 46.18 mV, when the mass ratio of zein to chitosan (HC) was 8:1. The encapsulation rate and the loading capacity were 82.93% and 8.29% under the optimal condition, respectively. SEM observation showed that most nanoparticles were in a regularly spherical shape and even distributed in the dispersion solution. FTIR revealed that hydrogen bonding and electrostatic interaction were the main forces for assembling nanoparticles. The formation mechanism of nanoparticles was that the Cur was scattered in the hydrophobic region of zein, whereas, chitosan surrounded the zein via the hydrogen bond and electrostatic interaction to prevent further aggregation. The chitosan greatly contributed to improving the pH, ion, and storage stability of nanoparticles for the extending application, such as nutrition and drug delivery. Specifically, optimal zeta potentials (46.2 to 41.8 mV) were achieved, as the dispersity index (0.042 to 0.025) decreased significantly during 60 days of storage at room temperature. At the same time, there were no significant changes in the particle size. It indicated that the prepared nanoparticles behaved better homogeneity and storage stability, suitable for the requirements of commercial application in the particles. The release results showed that the Cur-loaded composite nanoparticles presented a low release rate of 34.27% at the first 2 hours, while the release rate increased to 75.32% after 15 hours, and finally, 76.90% of Cur was found to be released after 48 h. Sustained-release properties were found in the Cur-loaded nanoparticles for the phosphate-buffered saline (PBS), compared with the free Cur. Consequently, the prepared zein-chitosan nanoparticles with excellent properties can be expected to serve as broad application prospects for nano-nutrient delivery in functional food and medicine. © 2021, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.