Fabrication and characterization of zein/tea saponin composite nanoparticles as delivery vehicles of lutein

The application of lutein hampers due to its environmental instability, poor water solubility and bioaccessibility. The goal of this paper was to overcome these challenges by fabricating zein/tea saponin nanoparticles act as the vehicles of lutein (ZTSLNPs). The optimized encapsulation efficiency of ZTSLNPs was 92.91%, while the loading capacity was 1.19%. The ZTSLNPs were smooth spherical structures with mean particle size of 213 nm and negative zeta-potential. Electrostatic interactions, hydrophobic interactions, and hydrogen bonding were the main forces to form ZTSLNPs. The encapsulated lutein in ZTSLNPs was amorphous. The secondary structure of zein was changed by incorporating lutein or tea saponin. ZTSLNPs showed great stability at pH 4.0-9.0, and exhibited excellent ionic strength stability and thermal stability. Meanwhile, the ZTSLNPs effectively reduced the decomposition of lutein during 15 days storage. Furthermore, ZTSLNPs showed excellent redispersibility. Besides, the water solubility and bioaccessibility of lutein were improved by ZTSLNPs. These findings indicated that the vehicle designed in our work would be a promising strategy to improving the application of hydrophobic functional factor.