UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
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Item DEVELOPMENT OF HORDEIN-PECTIN NANOPARTICLE COMPLEX FOR THE ENCAPSULATION OF BIOACTIVE COMPOUNDS FOR ENHANCED FUNCTIONALITIES(2023) Tarwa, Kevin; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nanoparticle delivery systems composed of food polymers are a sustainable and eco-friendly approach to protect functional ingredients and promote healthier food options. In this research, a hordein-pectin nanoparticle complex (HP-NPC) was fabricated using an anti-solvent precipitation and electrostatic deposition (pH 4) method for the encapsulation of hydrophobic bioactive compounds to enhance their functionalities. First, hordein was extracted from whole barley grains to obtain a dried powder to synthesize hordein nanoparticles (HNP). Then pectin with a degree of esterification (DE) around 71% was applied as a coating material. The average particle size of the freshly prepared nanoparticle complex was relatively small (~246 ± 11 nm), and Fourier transform infrared spectroscopy (FTIR) indicated that cationic hordein interacted with anionic pectin mainly though newly formed hydrogen bonds and electrostatic interaction as indicated by their opposite surface charges. Scanning electron microscopy (SEM) revealed that the morphology of the nanoparticle complex was spherical with a smooth surface. The pectin coating was shown to have a protective effect against pH (3.0-9.0), heat (80 °C for 0-120 mins), and salt (0-100 µM) which are all factors known to degrade proteins. Second, lutein, a hydrophobic bioactive xanthophyll was encapsulated into HP-NPC to develop a lutein-hordein/pectin nanoparticle complex (L-HP-NPC). Since lutein has low water solubility and low bioavailability in the gastrointestinal tract (GIT), the effect of the encapsulation system on the functional properties of lutein was investigated. The loading capacity (LC%) and encapsulation efficiency (EE%) was around 15.5 and 82%, respectively. In vitro digestion resulted in a higher bioaccessibility of lutein for encapsulated HP-NPC (~22.3%), which is defined as the percentage of lutein accessible for absorption in the simulated intestinal fluid (SIF) compared to lutein encapsulated into HNP (~9%). The ability of pectin to produce gels in acidic media was shown to have a significant effect against gastric enzymes that can degrade both hordein and lutein. Also, lyophilization (an important step in food processing) had no significant effect on the stability of L-HP-NPC. This encapsulation system could potentially be used as a functional ingredient in the food industry to develop healthy and nutritious foods for consumers. Third, carvacrol, a phenolic monoterpene known for its antimicrobial properties was encapsulated into HP-NPC to develop a carvacrol-hordein/pectin nanoparticle complex (CA-HP-NPC). Special focus was on the solubility of encapsulate carvacrol due to its known low solubility in aqueous solutions. The antimicrobial effectiveness of the encapsulated nanoparticle complex was tested against non-pathogenic gram-positive L. innocua and gram-negative E. coli K12. CA-HP-NPC was still able to maintain a relatively small particle size (~207 ± 8 nm) after being dispersed into water post-lyophilization. Carvacrol was shown to be effective against the two bacteria, however, CA-HP-NPC did not show antimicrobial effectiveness. Although carvacrol was successfully encapsulated into the nanoparticle complex, further studies on their release properties need to be investigated to further understand their functional properties for food applications.Item Semantics and pragmatics in a modular mind(2021) McCourt, Michael Sullivan; Williams, Alexander; Philosophy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation asks how we should understand the distinction between semantic and pragmatic aspects of linguistic understanding within the framework of mentalism, on which the study of language is a branch of psychology. In particular, I assess a proposal on which the distinction between semantics and pragmatics is ultimately grounded in the modularity or encapsulation of semantic processes. While pragmatic processes involved in understanding the communicative intentions of a speaker are non-modular and highly inferential, semantic processes involved in understanding the meaning of an expression are modular and encapsulated from top-down influences of general cognition. The encapsulation hypothesis for semantics is attractive, since it would allow the semantics-pragmatics distinction to cut a natural joint in the communicating mind. However, as I argue, the case in favor of the modularity hypothesis for semantics is not particularly strong. Many of the arguments offered in its support are unsuccessful. I therefore carefully assess the relevant experimental record, in rapport with parallel debates about modular processing in other domains, such as vision. I point to several observations that raise a challenge for the encapsulation hypothesis for semantics; and I recommend consideration of alternative notions of modularity. However, I also demonstrate some principled strategies that proponents of the encapsulation hypothesis might deploy in order to meet the empirical challenge that I raise. I conclude that the available data neither falsify nor support the modularity hypothesis for semantics, and accordingly I develop several strategies that might be pursued in future work. It has also been argued that the encapsulation of semantic processing would entail (or otherwise strongly recommend) a particular approach to word meaning. However, in rapport with the literature on polysemy—a phenomenon whereby a single word can be used to express several related concepts, but not due to generality—I show that such arguments are largely unsuccessful. Again, I develop strategies that might be used, going forward, to adjudicate among the options regarding word meaning within a mentalistic linguistics.Item FOOD PROTEIN-BASED NANOPARTICLES AS BIOAVAILABILITY ENHANCING ENCAPSULANTS(2015) Teng, Zi; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Proteins are attractive bioavailability enhancers for poorly absorbed nutraceuticals or drugs, owing to their natural abundance, amphiphilic nature, and desirable biocompatibility. This study systematically investigated the preparation, characterization, and application of protein-based nanoparticles as effective nutraceutical/drug carriers. Soy protein, one of the most widely utilized proteins, was firstly employed for preparing nanoparticles. The particle formation involved partial unfolding of protein molecules, limited aggregation in the presence of the antisolvent, crosslinking via chemical bonds, and refolding of the constituent monomers. Satisfactory encapsulation efficiency (EE) and time-dependent release of curcumin, a chemopreventive compound, were observed. The nanoparticles were further subjected to conjugation with folic acid, a cancer cell-targeting ligand. A pronounced increase in the accumulation in tumor cells such as Caco-2 was achieved upon folic acid conjugation, which demonstrated the potential of this technique for the targeted delivery of anti-cancer drugs. To overcome the rapid digestion of soy protein nanoparticles in the gastrointestinal tract, carboxymethyl chitosan was employed as a second coating layer by a simple ionic gelation method. The formed particles exhibited satisfactory EE for vitamin D3 and controlled releasing profile in vitro. Beta lactoglobulin (BLG) as another protein of interest is a major component of whey protein, serving as a natural carrier for lipophilic nutrients. Our study suggested that the interaction between BLG and curcumin could be promoted by tuning the antisolvent content. A loading capacity (LC) and EE of up to 11% and 98% respectively could be achieved under the optimal conditions. Moreover, nanoparticles prepared with cationic beta-lactoglobulin (CBLG) were able to transport most of the encapsulated drug intact through the gastrointestinal (GI) tract owing to its desirable particle integrity. Other advantages of CBLG-based systems included superior mucoadhesion, permeation across the small intestine epithelia, and cellular uptake. Finally, as CBLG molecules/nanoparticles absorbed the negatively charged serum proteins in the cell culturing medium, their surface properties, cytotoxicity, and cellular uptake were significantly altered. This series of studies not only demonstrated the efficiency and versatility of protein-based nanoparticles as bioavailability enhancers but also shed some light on the mechanisms for the encapsulation, transport, and delivery of nutraceuticals or drugs.Item Study of Electrostatic Interaction between Charged Surfactant Vesicles and Ionic Molecules by Bulk and Fluorescence Correlation Spectroscopy Measurements(2007-09-28) wang, xiang; English, Douglas; Chemical Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Phospholipid vesicles (Liposomes) for controlled release applications such as drug and gene delivery have attracted great interest. However, lack of long term stability and low solute encapsulation efficiency limit the usage of liposomes in many areas. In this thesis, charged surfactant vesicles that are formed spontaneously in mixtures of single-tailed surfactants are investigated as an alternative for liposomes in applications where improved long-term capture of charged organic molecules is desirable. The system of interest is dilute solutions of cetyltrimethylammonium tosylate (CTAT) and sodium dodecylbenzenesulfonate (SDBS). It is shown that charged surfactant vesicles have a high efficiency for encapsulating oppositely charged probe molecules with extremely slow release rates. Several probe molecules, both anionic and cationic, were studied including the cancer chemotherapeutic drug doxorubicin (Dox). All probe molecules were captured at high efficiency (ca. 20-70%) when the vesicle bilayer was of opposite charge from the probe molecule; when the charge of vesicle and probe molecule was the same, encapsulation was diminished (ca. 0-8%). Strong electrostatic interaction between surfactant vesicles and charged molecules are responsible for the extremely high encapsulation efficiency. The vesicle/probe formulations are stable for weeks to months due to the inherent stability of these vesicles which form spontaneously and are believed to be equilibrium structures. These properties allow surfactant vesicles to be used to selectively separate oppositely charged dye molecules, and this is demonstrated. Fluorescence correlation spectroscopy (FCS) was used to gain deeper understanding into the role of electrostatics in the capture of charged probe molecules by charged surfactant vesicles. FCS measures the diffusion of fluorescent probe molecules in aqueous solutions at very low concentrations (10-9-10-8 M) and distinguishes between rapidly diffusing single molecules and slowly diffusing molecules that are adsorbed on a vesicle bilayer. This method is sensitive enough to rapidly determine the fraction of probe molecules bound to the bilayer interface in a given sample. Binding isotherms were constructed from FCS measurements in which a series of solutions were measured by holding the dye concentration constant while increasing the vesicle concentrations. The resulting isotherm yields a measure of binding energy. Comparisons of binding energies show that probe/bilayer interactions are mainly governed by charge-charge interactions but may also depend on the size and structure of the surfactant counter ions. Our findings provide useful guidelines for implementing surfactant vesicles in biotechnological applications and also serve as an intriguing example of charge-mediated bilayer interactions.