Interaction Mechanism of Zein with Oridonin and Preparation and Characterization of Zein-Oridonin Nanoparticles

Using zein as carrier, the oridonin-loaded nanocarriers were developed with the objective of increasing its solubility and bioavailability in this study. Firstly, the interaction mechanism between oridonin and zein was studied by multispectral method. Then, oridonin-loaded zein-based nanoparticles (Zein-ORI-NPs) were prepared by antisolvent method and were characterized by laser particle size analyzer, scanning electron microscope, differential scanning calorimetry, X-ray diffraction and fourier transform infrared spectroscopy. The results showed that ORI could quench intrinsic fluorescence of zein through a static quenching procedure of non-radiative energy transfer. The number of binding sites n was close to 1, indicating that ORI and zein were combined in 1:1 form. The binding force of ORI and zein was mainly hydrogen bond and van der waals force, and the interaction between them was spontaneous. Multispectral analysis also confirmed that the addition of ORI could affect the microenvironment around the tryptophan residue in zein, resulting in changes in the conformation of zein. Zein-ORI-NPs were spherical in shape, with small particle size, uniform distribution and good stability. The encapsulation efficiency of ORI in Zein-ORI-NPs were more than 70%. The main driving force for the formation of Zein-ORI-NPs was non-covalent interaction such as hydrogen bonding, and ORI was successfully embedded in nanoparticles in a non-crystalline state, which improved the thermal stability of nanoparticles. These findings can provide a reference for designing zein-based delivery systems to encapsulate and protect ORI, while laying a foundation for developing functional ORI products.