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Title: Carbohydrate-silica nanoparticles for sirna delivery : synthesis, characterization, and gene delivery
Creator: Chesniak, Olivia Mariel
Date: 2019
Collection: Electronic Theses & Dissertations
Description: RNA interference (RNAi) has long been pursued for its therapeutic potential. Sequence-specific knockdown of gene expression requires that small interfering RNA (siRNA) gain access to cellular cytoplasm, presenting difficulties for both the transport of nucleic acids to cells and their voyage across cellular membranes. Numerous materials are under development as siRNA delivery vehicles to address this need. The carbohydrate dextran has been incorporated into amine-functionalized sil- ica...
Show moreRNA interference (RNAi) has long been pursued for its therapeutic potential. Sequence-specific knockdown of gene expression requires that small interfering RNA (siRNA) gain access to cellular cytoplasm, presenting difficulties for both the transport of nucleic acids to cells and their voyage across cellular membranes. Numerous materials are under development as siRNA delivery vehicles to address this need. The carbohydrate dextran has been incorporated into amine-functionalized sil- ica nanoparticles (Dex-SiO2-NPs), enhancing their biocompatibility and success as siRNA delivery vehicles. Inspired by the work of Stober and others, reagent concentrations in the synthesis of Dex- SiO2-NPs have been adjusted to tune nanoparticle diameter. The size, shape, and morphology of Dex-SiO2-NPs have been characterized using transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy (EDS). These methods have revealed that Dex-SiO2-NPs decrease in silicon density toward their centers, when compared with SiO2-NPs. Thermal and porosity analysis were used to profile Dex-SiO2-NPs both containing dextran and after its removal by calcination. Having measured an increase in mesopores and decrease in micropores with calcination, it has been concluded that dextran serves as a porogen in Dex-SiO2-NP synthesis. Not only does dextran imbue these materials with unique morphology, it also enhances their function as delivery vehicles. Dex-SiO2-NPs improve enhanced green fluorescent protein (EGFP) supression compared to silica nanoparticles synthesized in the absence of dextran in human lung and kidney cells in vitro.
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Title: Crystallization of silica gel in the presence of lithium salts
Creator: Shah, Balkumar Prataprai, 1939-
Date: 1970
Collection: Electronic Theses & Dissertations

Title: Supramolecular assembly of mesoporous silicas with neutral amine surfactant structure directors : synthesis and characterization
Creator: Pauly, Thomas Ralph
Date: 2000
Collection: Electronic Theses & Dissertations

Title: Local structure of intercalants and host nanoporous materials
Creator: Shatnawi, Mouath Ghazi
Date: 2007
Collection: Electronic Theses & Dissertations

Title: The apparent density of silica gel measured in various liquids
Creator: Leisy, Reuben Warren
Date: 1929
Collection: Electronic Theses & Dissertations

Title: Design, synthesis and catalytic applications of mesoporous silica molecular sieves
Creator: Zhang, Wenzhong
Date: 2000
Collection: Electronic Theses & Dissertations

Title: Toward phosphorylated peptide enrichment based on organofunctionalized mesostructured silica
Creator: Lee, Dong-Keun
Date: 2009
Collection: Electronic Theses & Dissertations

Title: The effects of hydrated ferric oxide on the adsorptive capacity of silica gel
Creator: Jasper, Joseph John
Date: 1927
Collection: Electronic Theses & Dissertations

Title: The heat of adsorption of hydrated silica gel
Creator: Nasif, Mack Machail
Date: 1931
Collection: Electronic Theses & Dissertations

Title: A new microporous silica : its intercalation in magadiite
Creator: Baviére, Astrid
Date: 1992
Collection: Electronic Theses & Dissertations

Title: Functionalization of mesoporous molecular sieves assembled using non-ionic surfactants and water soluble silicates : synthesis and characterization
Creator: Shah, Jainisha R.
Date: 2001
Collection: Electronic Theses & Dissertations

Title: Fundamental studies of competitive equilibria at silica surfaces
Creator: Stubbs, Barrack Perez
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "The fundamental interactions such as physisorption at solid-liquid interfaces are not fully characterized. The physical properties and chemical reactivity at the silica surface is one that is subject to much investigation. A variety of analytical techniques, including solid state nuclear magnetic resonance (SS-NMR ) and high-performance liquid chromatography (HPLC) were utilized to help characterize the surface of silica. These techniques were combined in order to understand the fundamental...
Show more"The fundamental interactions such as physisorption at solid-liquid interfaces are not fully characterized. The physical properties and chemical reactivity at the silica surface is one that is subject to much investigation. A variety of analytical techniques, including solid state nuclear magnetic resonance (SS-NMR ) and high-performance liquid chromatography (HPLC) were utilized to help characterize the surface of silica. These techniques were combined in order to understand the fundamental mechanisms of surface interactions such as adsorption mechanisms and chemical reactivity. The pH, ionic strength, and mobile phase compositions were varied throughout the experiments as a basis for assessing reactivity.The SS-NMR data shows a correlation between pH and labile surface hydrogens. At higher pH values, the transfer of excitation from labile surface hydrogens to surface silicon atoms is diminished. A change in peak ratios that correspond to labile primary silanols and surface bridging siloxanes was observed. The relative concentration of bridging siloxanes is constant whereas the signal from primary silanols is greatly diminished.Aqueous, normal-phase HPLC shows the various interactions of phenol with the silica surface. Multiple peaks were generated from a single analyte when the water/methanol concentration was at least 20%/80%. At 90% and 100% methanol, a single peak is shown for phenol. The ratio and number of peaks depends on conditions such as solvent composition, pH, ionic strength, flow rate, and temperature. We argue that the distribution of surface silanol sites is responsible for the generation of multiple peaks that are seen in the extreme aqueous conditions. These sites, as well as the water in the mobile phase, modify the mass transport term in the Van Deemter equation. The conditions and results obtained in these experiments are explained below with an emphasis on mass transport.Additionally, other analytical techniques such as scanning electron microscopy, thermogravimetric analysis, and inductively coupled plasma were used to help characterize the silica surface. Through these techniques, values for surface silanol concentration ranging from 1.6micromole/m2 to 7.0micromole/m2 were obtained. The physical morphology of the silica surface was also characterized before and after exposure to basic environments."--Pages ii-iii.
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Title: Synthesis and properties of substituted polylactides and surface functionalization of small silica nanoparticles
Creator: Zhang, Quanxuan
Date: 2013
Collection: Electronic Theses & Dissertations
Description: ABSTRACTSYNTHESIS AND PROPERTIES OF SUBSTITUTED POLYLACTIDES AND SURFACE MODULATION OF SMALL SILICA NANOPARTICLESByQuanxuan ZhangPolylactides have been widely studied as a degradable material in environmental and biomedical fields due to their biodegradability and biocompatibility. However, the applications of polylactide has been limited by its high crystallinity, hydrophobicity and lack of functionalization; so strategies that provide routes to functionalized polyesters are necessary to...
Show moreABSTRACTSYNTHESIS AND PROPERTIES OF SUBSTITUTED POLYLACTIDES AND SURFACE MODULATION OF SMALL SILICA NANOPARTICLESByQuanxuan ZhangPolylactides have been widely studied as a degradable material in environmental and biomedical fields due to their biodegradability and biocompatibility. However, the applications of polylactide has been limited by its high crystallinity, hydrophobicity and lack of functionalization; so strategies that provide routes to functionalized polyesters are necessary to produce materials with the desired physical and chemical properties. Development of those strategies has been one of the major efforts to expand the application of polylactides, especially as degradable delivery vehicles. A series of propargyloxy lactic acid derivatives using poly(ethylene glycol) with different lengths as spacers between propargyl group and lactic acid were prepared with high yield via hydrolysis of cyanohydrin from inexpensive starting materials without using column purification. The versatility of the developed method was also tested by the survival of alkene group in the synthesis of allyloxy lactic acid. An azido lactic acid was also prepared to act as an alternative approach to render click function to polylactides. This allows for easy access of building up a library of clickable α-hydroxy acids to prepare clickable substituted polylactides.Post-polymerization modification via click chemistry provides a convenient route to functionalized polylactides with a variety of new properties. We prepared clickable polylpropargyloxylactide that have pendant propargyl groups available for the attachment of chemical functionality using click chemistry without degradation of polymer backbones. The clicked degradable polylactides have thermo-responsive properties with lower critical solution temperatures (LCST) from room temperature to 68 oC. The prepared amphiphilic copolymers, mPEG-b-polypropargyloxylactide were self-assembled into micelles which were core cross-linked to improve the structural stability of the micelles with better controlled release of cargo molecules and response to the reducing reagent.The relationship between the glass transition temperature (Tg) of polylactide and its backbone structure was studied. The direct attachment of rigid and bulky substituents can be used to tune the Tg and thermal properties of polylactides and broaden the scope of their physical properties.Silica nanoparticles (SiNPs) have attracted much attention due to their chemical inertness, low or non toxicity, excellent thermal stability and especially, easy access of surface functionalization. A facile grafting route was developed to prepare stably mono-dispersed SiNPs in aqueous media via click chemistry. Different sized SiNPs were grafted with a broad range of surface chemistries (carboxylic acids, amines, alcohols and methoxy-terminated polyethylene glycol chains). The resulted SiNPs were purified by dialysis and stably dispersed in water and in vitro cell culture media with narrow size distributions and no aggregation.
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Title: Anodic growth and cathodic removal of silicon dioxide layers utilizing an electron cyclotron resonant microwave plasma disk reactor
Creator: Salbert, Geoffrey Todd
Date: 1992
Collection: Electronic Theses & Dissertations

Title: Design, fabrication, and utilization of silica inverse opal structures for flow-through catalyst supports
Creator: Gornowich, Douglas B.
Date: 2013
Collection: Electronic Theses & Dissertations
Description: Enzymes are used in a wide range of industries for various different chemical processes. Optimizing the performance of enzymes remains an area of high interest in many research labs. An enzyme is often immobilized on or within a support structure, which allows for the biocatalyst to be relatively easy to recover post-reaction. Immobilization can also increase the structural stability of the enzyme, which is beneficial from a cost standpoint because pure enzymes can be expensive. By choosing...
Show moreEnzymes are used in a wide range of industries for various different chemical processes. Optimizing the performance of enzymes remains an area of high interest in many research labs. An enzyme is often immobilized on or within a support structure, which allows for the biocatalyst to be relatively easy to recover post-reaction. Immobilization can also increase the structural stability of the enzyme, which is beneficial from a cost standpoint because pure enzymes can be expensive. By choosing the appropriate support and immobilization chemistry, it is possible to maximize the efficiency of a biocatalyst. The purpose of this work was to design, fabricate and utilize inverse opal structures as a support for the immobilization of enzymes. We have developed a flow-through silica inverse opal structure that was used for the immobilization of biocatalysts. The inverse opal structures were created using polystyrene nanospheres as a template, sol-gel chemistry to deposit silica in the interstitial spaces between the nanospheres, and solvent dissolution to remove the template. Scanning electron microscopy and dynamic light scattering were used to characterize the nanospheres and structures. The silica inverse opal structure has a relatively high surface area, and a surface that is amenable to a wide range of surface modification reactions. Two enzymes were chosen to evaluate our catalyst support structure; glucose oxidase and alkaline phosphatase. Absorbance and fluorescence measurements were used for the enzyme assays. Our results show an enhancement in reactivity that is associated with enzyme immobilization and nano-confinement, and also underscore limitations inherent to this approach. Three different reaction formats were examined: solution phase, immobilized enzymes on planar supports, and enzymes immobilized on the flow-through inverse opal structure. Glucose oxidase exhibited an increase in reactivity when comparing planar vs. solution phase and inverse opal vs. planar structural formats. This finding indicated an enhancement due to the immobilization process and due to the nanoconfinement of the enzyme within the inverse opal structure. In contrast, alkaline phosphatase exhibited a reduced activity when comparing solution phase vs. enzyme immobilized on planar and inverse opal structures. This finding illustrated the importance of identifying immobilization chemistry that maintains the enzyme in an active form and binds the enzyme in a way that leaves the reactive site accessible. An enhancement was observed for the inverse opal structure vs. the planar support, indicating that there remains the positive effect associated with nano-confinement of the enzyme. This project proved to be enlightening by showing the enhancements in activity for glucose oxidase, and also by showing that there are limitations that need to be addressed in the alkaline phosphatase results. There will be continued work to further characterize and optimize the flow-through inverse opal structures. In addition, it may be useful to examine the use of other materials for the inverse opal support itself. The results of this work are promising for the utilization of inverse opal structures to immobilize and optimize the performance of enzymes.
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