Improving the bioaccessibility of naringenin using biopolymer delivery systems
Creators: name: Liu, Lang
Publisher: name: No Publisher Supplied
Year: 2021

description: Naringenin (5,7,4’-trihydroxyflavonone) (NAR) belongs to the category of citrus flavonoids. It possesses many excellent pharmacological effect, the preferred bioefficacies of naringenin are anti-oxidant, anti-inflammation, neuroprotective et al. Although NAR possesses many excellent pharmacological activities, it belongs to Biopharmaceutics Classification System (BCS) class II which a type of nutraceuticals that have poor water solubility and degrade easily, resulting a relatively low bioavailability. In order to improve the bioaccessibility of NAR, I designed a novel food derived protein polysaccharide based nanocomplexes which were fabricated by beta-lactoglobulin (BLG) and oligochitosan (OCS). In the first part of this research, we investigated the interaction between BLG and NAR using both chemical experiments and computer simulations. For the chemical experiments, the fluorescence quenching study and circular dichroism were engaged and we can know the binding number between BLG and NAR and the secondary structure change from the macroscale dimension. Many detailed molecular level information can be obtained through the computer simulations which we cannot get them from the chemical experiments. By using Molecular Docking (MD), this is one molecule interaction, we can know the binding sites between BLG and NAR. By using Replica Exchange Monte Carlo (REMC), this can simulate multiple molecules interaction which is similar to the real drug delivery system, we can know the binding behaviors such as visualization trajectories of binding, probability and selectivity of binding, the weight and size changes of complexes, the top ranked prominent regions. Additionally, we can also know the binding number which can be mutually verified with the results of chemical experiments. Therefore, the research in this part connects the macroscale phase to the perspective of molecular level to obtain a more comprehensive understanding of the interaction between BLG and NAR.In the second part of the research, BLG and OCS can self-assemble into nanoparticles through electrostatic interaction at pH 7.4 which close to the pH value of the physiological environment of human body. The interaction between BLG and OCS have been investigated through pH-turbidity titration, dynamic light scattering (DLS), atomic force microscope (AFM), circular dichroism (CD). NAR was successfully encapsulated in the BLG/OCS nanoparticles, aiming to protect NAR from degradation under the environment of small intestinal (neural pH). The results showed that NAR first associated with BLG mainly through hydrophobic interaction. The BLG/NAR complexes then interacted with OCS by electrostatic interaction to form the nanoparticles with the particle size was in the range of 200-350 nm under pH 7.4. NAR was effectively encapsulated in the BLG/OCS nanocomplexes with more than 90% encapsulation efficiency. The cell viability of NAR loaded NPs was concentration-dependent, the more NAR loaded NPs added, the lower cell viability they would be. The cellular uptake was time dependent, at the time intervals of 6 to 9 hours, there was the largest amount of NPs endocytosis.In the third part of this research, in order to increase the stability and loading capacity, the PE was applied and stabilized by BLG/OCS NPs. Because the driven force between protein and polysaccharide is electrostatic interaction, so at low pH, the particles will dissociate, resulting was not stable at low pH. To solve this problem, I used a natural crosslinker – genipin, to covalent crosslink BLG and OCS. When the genipin concentration reached 0.5 mg/ml, the particle size can be as low as 250 nm with the crosslinking time was 10 hours. The contact angle was between 30-40 degree when the crosslinking time was less than 20 hours which indicated that the pe can be regarded as stable. I also investigated the effect of protein concentrations, oil fraction and crosslinking time on the microstructure change of GNPs based PE. The size of PE after crosslink did not change too much when the pH went from 2 to 7.4 by compared with the uncrosslinked samples. Which means the pH stability of pe has been greatly enhanced after crosslink with genipin. Then I used two in vitro methods – pH-lipolysis and Tim-1 to test whether the bioaccessibility of NAR has been improved or not after formulated. The tested bioaccessibility for pH-lipolysis was higher than Tim-1 measured. Because TIM-1 model has taken more factors into consideration. Such as peristalsis movement, GI residence time, passive absorption and elimination. Therefore, its result was a little lower than that of pH-lipolysis. However, no matter in which method, the bioaccessibility of NAR had been enhanced 3.5 times more than that by comparison with oil suspension samples and jejunum is the major organ for absorption.To sum up, my Ph. D study provides a potential delivery system to solve the low bioaccessibility of nutraceuticals via oral route. This strategy can also be applied in utilizing other kinds of hydrophobic nutraceuticals. This study also provides a computer based approach – REMC which can exhibit many detailed information and dynamic visualization about the binding behaviors of bio-macromolecules and small bioactive molecules.