|Title:||Development of hydrophobic films, super-hydrophobic nanofibrous networks, and drug encapsulation systems from zein with enhanced properties for applications in biomedical engineering|
|Advisors:||Wang, Yi (ABCT)|
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Applied Biology and Chemical Technology|
|Pages:||xvii, 123 pages : color illustrations|
|Abstract:||Zein, a major protein extracted from corn, is an abundant and reproducible biopolymer which has excellent mechanical properties and biocompatibility. It has been widely applied in food and pharmaceutical industrials. In this study, the hydrophobic films, super-hydrophobic nanofibrous networks,and drug encapsulation systems were developed from zein to obtain enhanced properties for applications in biomedical engineering. In chapter 2, zein was used to form surfaces with high hydrophobicity through self-assembly monolayer (SAM) assisted EISA. The present method is facile and inexpensive. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) were applied to characterize the morphology and the elements of the formed zein surfaces, respectively. Water contact angle (WCA) values of the formed zein surfaces were also measured to study the hydrophobicity of formed zein surfaces. The effects of both the concentrations of zein solutions and solvent on the WCA values of the formed zein surface were investigated. A zein surface with a high WCA value (126°) was also formed through size controlled SAM assisted EISA. In chapter 3, zein super-hydrophobic/hydrophobic nanofibrous networks were formed by electrospinning. The formed zein networks showed high hydrophobicity with the WCAs ranging from 130.5° to 153.6°. The cell attachment and growth on the zein networks were studied. It was observed that the amount of the cells attaching and growing in the zein nanofibrous networks were higher than the ones on the conventional zein casting films. The results indicated that the electrospun zein nanofibrous network had great potential as scaffolds in tissue engineering to support cell growth and tissue regeneration. In chapter 4, super-hydrophobic/hydrophobic surfaces were formed from zein by electrospinning. WCA and SEM were used to characterize the hydrophobicity and surface morphology. The highest WCA of the zein electrospun surfaces could reach 155.5°. A formation mechanism was proposed based on the orientation of the amphiphiles during the solvent evaporation of different fabrication methods. The droplet-based or jet-based evaporation during electrospinning and spray drying leaded to the formation of the super-hydrophobic/hydrophobic surface by the accumulation of the hydrophobic groups of the amphiphiles on the surface, while the surface-based evaporation during cast drying leaded to the formation of the hydrophilic surface by the accumulation of the hydrophilic groups of the amphiphiles on the surface.In chapter 5, a double-layer zein/CS structure was utilized to encapsulate vitamin C (VC). VC was first encapsulated by chitosan (CS) with sodium tripolyphosphate(STPP).Then zein was added to coat the formed VC-loaded CS nanoparticles (NPs). The formed VC-loaded zein/CS microspheres (MPs) had a good sphericity with particle size ranging from 720 to 1100 nm. VC was greatly protected from degradation by the double-layer coating and only 5% of VC was oxidized after 10-day storage at room temperature. The double-layer structure also had a better performance on retarding the release of VC in simulated gastric fluid (SGF) and achieving controlled release in simulated intestinal fluid (SIF), which provided a method for further utilization of nutrients in human body.|
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