Development of hordein-based delivery vehicles to improve the absorption of phytochemicals
Creators: name: Zhang, Junjia
Publisher: name: No Publisher Supplied
Year: 2024

description: Growing awareness regarding the impacts of diet on human health has led to expanding consumer demands for incorporating of healthy ingredients and nutraceuticals into food and beverage products. Among which, phytochemicals are a promising class of nutraceutical candidates with numerous health-promoting efficacies. However, the integration of phytochemicals toward food and beverage products can often be challenged with unpleasant sensory profiles, incompatibility with food matrixes, limited absorption, etc. As a result, rational design of appropriate delivery strategies is thus crucial to ensure the proper incorporation and consumption of phytochemicals. Hordein, the major prolamin protein found within barley grains, is of great interest in this thesis as a biomaterial building block with great potential due to its appealing and unique properties: sustainable, biodegradable and biocompatible status, strong hydrophobicity, self-assembly capability, reduced susceptibility to gastrointestinal digestions, controlled release behaviors, and more. Therefore, with the aims to develop functional hordein-based biomaterials and to investigate their application potential in improving the absorption of phytochemicals, this thesis is composed with contents in 1) acquisition of hordein from barley grains and assembly of hordein-hyaluronic acid (H-HA) complexes, 2) analysis of in vitro bioaccessibility and bioactivity of dihydromyricetin-hordein-hyaluronic acid (DMY-H-HA) complex nanoparticles as delivery system for dihydromyricetin, 3) modification of hordein by lauric acid and fabrication of hordein colloidal particle based Pickering emulsions, and 4) development of hordein-based Pickering double emulsions for co-encapsulation of water-soluble and lipid-soluble nutraceuticals. Specifically, the thesis started with the extraction of hordein from barley grain flour, and the protein content as well as polypeptide composition of the extracted hordein were confirmed using the Kjeldahl method and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Subsequently, H-HA complexes were successfully assembled through liquid-liquid dispersion combined with electrostatic deposition. Investigations toward the physiochemical characteristics revealed that H-HA complexes exhibited reduced particle size and polydispersity and enhanced zeta-potential, when compared to single-layer hordein nanoparticles. Meanwhile, it was found that electrostatic interaction, hydrogen bonding, and hydrophobic interaction were responsible for the corresponding protein-polysaccharide complex formation. Moreover, in comparison to single-layer hordein nanoparticles, H-HA was demonstrated with improved stability profiles regarding various environmental conditions. In addition, dihydromyricetin (DMY) is a plant flavonoid with numerous health-beneficial properties, however, its application potential could be challenged by its limited bioavailability. Therefore, H-HA was further utilized and assessed as a nanoparticle delivery system for DMY (DMY-H-HA). In this study, the physiochemical characteristics of the DMY-H-HA were evaluated, the morphology of the complex nanoparticles was observed with scanning electron microscopy (SEM), and the encapsulation and loading profiles were also determined. Through in vitro and ex vivo investigations, it was found that DMY-H-HA exhibited enhanced gastrointestinal dissolutions and intestinal permeations compared to that of the unencapsulated DMY. Additionally, the absorption pattern of the complex nanoparticles was clarified by the Caco-2 cells cellular uptake study, and anti-inflammatory analyses with RAW 264.7 macrophage cells also suggested the improved bioactivity of DMY-H-HA compared to DMY aqueous suspension. Results gathered from this study demonstrated the capability of DMY-H-HA as a delivery system for DMY, while also providing additional support for the applicability of hordein for functional food and beverage considerations. In the following section, lauric acid-modified hordein (LAH) colloidal particles were prepared by antisolvent co-precipitation into the alkali environment. LAH colloidal particles and the influences of lauric acid were characterized, and lauric acid was found to be effective regarding hydrophobic modification of the hordein particles. Meanwhile, hordein-based oil-in-water (O/W) Pickering emulsions were fabricated with the prepared colloidal particles and evaluated systematically; It was demonstrated that the colloidal particle, particle concentration, and oil phase fraction can exert significant impacts on the stability, microstructure, and rheological property of the fabricated emulsions. More importantly, robust high internal phase Pickering emulsion was also achieved in this study, as superior stability, enhanced droplet packings, and elastic and gel-like behaviors were determined to be associated with such emulsions at elevated levels of oil phase fraction. For instance, hordein-based water-in-oil-in-water (W1/O/W2) Pickering double emulsions (HPDE) were developed for co-encapsulation of water-soluble riboflavin and lipid-soluble carnosic acid (CA). Formulation developments were carried out for the respective primary and secondary emulsions, and the impacts of formulation parameters were investigated. At the same time, the droplet structure, interfacial morphology, and cross-section of the HPDE were visualized using cryo-scanning electron microscopy (Cryo-SEM). Moreover, HPDE exhibited satisfactory encapsulation stability and release profile under simulated gastrointestinal conditions for the W1 encapsulated riboflavin. On the other hand, HPDE was indicated with a more rapid rate of in vitro lipolysis and resulted in enhanced bioaccessibility of the oil phase loaded CA, compared to that suspended in the bulk oil. In addition, when applied to digestions using the TIM-1 dynamic gastrointestinal model, HPDE had led to 2.0- and 2.5-fold increases in the cumulative bioaccessibility of the encapsulated CA in the jejunum and ileum compartment, respectively, in comparison to that of the unencapsulated format.