*3.4. Encapsulation of 7,8-DHF*

The influence of polysaccharide types (CMC and ALG) and 7,8-DHF concentration on PDI value, particle size, EE and LC value in different delivery systems were summarized in Table 1. When the mass ratio of 7,8-DHF to zein was 1:5, the EE and LC of DHF-S/Z were 82.42 and 7.49%, respectively. However, compared to DHF-S/Z, DHF-CMC/S/Z and DHF-ALG/S/Z exhibited better EE value, especially DHF-CMC/S/Z nanoparticles (88.63%) (*p* < 0.05). These findings suggested that polysaccharide addition improved the embedding ability of S/Z via non-covalent interactions. There are two hydroxyl groups in the 7,8-DHF molecule that can interact with the hydroxyl groups of polysaccharides and the tyrosyl of zein. These interactions can form hydrogen bonds, possibly resulting in an increase of EE. These phenomena indicated that polysaccharides and S/Z showed a synergistic effect on the EE of 7,8-DHF. When mass ratio of 7,8-DHF to zein was 1:10, three colloidal delivery systems possessed high EE for 7,8-DHF (above 98.21%). In contrast to unloaded colloidal delivery systems, the particle size of loaded colloidal delivery systems was growing when increasing the mass ratio of 7,8-DHF to zein. In general, 7,8-DHF, as a hydrophobic compound, is expected to be located within hydrophobic region of zein, ultimately possessing an impact on the size and stability of particles. 7,8-DHF encapsulation might impair interactions among hydrophobic groups of zein and increase particle size. Additionally, the encapsulation of 7,8-DHF caused an increase of PDI value in contrast to unloaded complexes. A uniform result was reported by Sun et al. [37]. The formation of free 7,8-DHF aggregates might help to explain the above observed phenomenon.


**Table 1.** EE, LC, particle size and PDI of 7,8-DHF in different colloidal systems.

Values are the means ± SD (*n* = 3). a–e: Different letters in the same column indicate significant differences (*p* < 0.05) based on one-way ANOVA analysis followed by Tukey's honest significant difference post hoc tests.
