Development of food polymer-based colloidal delivery systems for nutraceuticals
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Colloidal delivery systems have drawn increasing attention in food science area. Biopolymers, i.e. proteins and polysaccharides originated from foods, with low toxicity, high biocompatibility and biodegradability, are the ideal biomaterials to develop delivery systems for nutraceuticals. The present work is dedicated to develop delivery systems for nutraceuticals, using food derived biopolymers, e.g. chitosan and zein. In the first part of this study, different core-shell structured nanoparticles were developed for encapsulating both hydrophilic and hydrophobic nutracetuicals. For chitosan nanoparticles with zein coating, the hydrophilic nutraceutical, selenite, was encapsulated and the physicochemical properties was improved after zein coating. Then, zein nanoparticles with chitosan (CS) or carboxymethyl chitosan (CMCS) coating were developed to encapsulate hydrophobic nutraceuticals, including vitamin E, vitamin D3, indole-3-carbinol and diindolylmethane. The fabrication parameters were systematically studied and the effects of encapsulation on stabilities of nutraceuticals were investigated under different conditions. Subsequently, a novel approach to prepare CMCS hydrogel beads was developed. CMCS, a water-soluble derivative of CS, was known as unable to form hydrogel beads by itself in aqueous solution due to chain rigidity and inefficient entanglement. In this part, the formation of CMCS hydrogel beads was studied in aqueous-alcohol binary solutions. Chemical crosslinking was required to maintain its integrity upon drying. Different drying methods (i.e. freeze and air drying) were also investigated to understand their effects on swelling and release profile in simulated gastrointestinal conditions. Some possible mechanisms were discussed. Lastly, cellular evaluation of zein nanoparticles stabilized by caseinate was carried out. The zein-caseinate nanoparticles had a good redispersibility after freeze-drying and were able to maintain original particle size in different cell culture medium and buffer at 37°C over time. The zein-caseinate nanoparticles had no cytotoxicity at concentrations up to 1 mg/ml over 3 days. Then, coumarin 6, a fluorescent marker, was encapsulated into zein-caseinate nanoparticles to investigate their cell uptake and epithelial transport. The cell uptake was clearly visualized by fluorescent microscopy and the uptake mechanisms were investigated. The epithelial transport was investigated on Caco-2 cell monolayers. The results suggested caseinate not only stabilized zein nanoparticles in different buffers, but also improved cell uptake and epithelial transport.