Text

theses

In this dissertation, a novel polysaccharide-polypeptides nanocomplex was assembled from chitosan (CS) and caseinophosphopeptides (CPPs). CS is a biodegradable, biocompatible, and non-toxic cationic polysaccharide. CPPs are a group of anionic bioactive polypeptides hydrolyzed from caseins, which are the most abundant proteins in milk. CS and CPPs can self-assemble into complexes through predominantly electrostatic attraction when they are oppositely charged. In the first part of this dissertation, the black tea polyphenol theaflavin-3,3’-digallate (TF-3) was encapsulated in the CS-CPPs nanocomplex, aiming to improve its intestinal permeability. The interactions and microstructural changes involved in each step of the encapsulation process were characterized by multiple techniques including turbidimetric titration, fluorescence quenching, circular dichroism, quartz crystal microbalance with dissipation monitoring, small angle X-ray scattering, and ultra-small angle X-ray scattering. The results indicated that TF-3 firstly associated with CPPs through mainly hydrogen bond. The TF-3/CPPs mixture further interacted with CS via predominantly electrostatic interactions. TF-3 was then encapsulated in the CS-CPPs nanocomplex with high encapsulation efficiency. The CS-CPPs nanocomplex can effectively enhance the intestinal permeability of TF-3. As the CS-CPPs nanocomplexes were associated predominantly by electrostatic attraction, which is susceptible to pH change. To prevent the low pH-induced disassemble of the nanocomplexes and burst release of the encapsulated TF-3, the nanocomplexes encapsulated with TF-3 were chemically crosslinked by genipin. The Caco-2 monolayer transport results demonstrated that the cumulative amount of transported TF-3 during 2h experiment increased at least 7.8 folds after being encapsulated in the crosslinked nanocomplexes. In the second part of this dissertation, the CS-CPPs nanocomplexes composed of different CS:CPPs weight ratios were applied to stabilize Pickering emulsions. These gel-like oil-in-water type Pickering emulsions, however, were not stable at low pH due to disassembly of the nanocomplexes. To solve this problem, the CS-CPPs nanocomplexes were crosslinked with genipin at different conditions. These genipin crosslinked CS-CPPs nanocomplexes (GCNs) were further applied to stabilize Pickering emulsions, which showed outstanding stability in a wide pH range. After incorporation of TF-3 in the GCNs, the stability of Pickering emulsions against lipid oxidation has been improved significantly.

ETD_8509

Ph.D.

Includes bibliographical references

Includes vita

doi:10.7282/T3B56NV8

ETD doctoral

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