Layered double hydroxide-organic hybrids as water-soluble mamocomposites for drug delivery

Atlanta University and Clark Atlanta University Theses and Dissertations
Layered double hydroxide-organic hybrids as water-soluble mamocomposites for drug delivery
Bolton, Ladena A. (Holley)
Date of Original:
Degrees, Academic
Dissertations, Academic
United States, Georgia, Fulton County, Atlanta, 33.749, -84.38798
Degree Type: dissertation
Degree Name: Doctor of Philosophy (PhD)
Date of Degree: 2014
Granting Institution: Clark Atlanta University
Department/ School: Department of Chemistry
A series of sulfonated polystyrene-layered double hydroxide (PSS-LOH) nanocomposites have been prepared and characterized, in order to analyze structure-property relationships of polymer LOH composites, based on differences in charge density and molecular weight of the macromolecule. Ultimately, understanding of these relationships will be used as a tool to achieve target properties for a specific application, namely drug delivery. In this study, sulfonated polystyrene is a random copolymer composed of various fractions (or percentages) of both polystyrene and sulfonated polystyrene units. Varying the structure of PSS and the preparation method of the PSS-LDH nanocomposites is useful for influencing crystallinity; and controlling particle size, d-spacing, binding strength and the drug release rate of the nanocomposites. X-Ray diffraction crystallographic measurements indicate that for polystyrene with sulfonation levels less than 13% and molecular weight higher than 8xl 03 gmol"1 , adsorption of the macromolecule occurs at the surface of the LDHs, resulting in a reduction in stability as determined by thermogravimetric analysis and NMR spectroscopy. However, at a minimum of approximately 13% sulfonation of8x103 gmor1 polystyrene, polymer-LOH interactions become more favorable relative to the properties exhibited by pristine LOH. These properties include small particle size measured by dynamic light scattering, higher thermal stability and an increase in charge transfer between PSS and LDH. Drug release studies from the optimal PSS/PEG-LDH composite with model drug Rhodamine B base (RhBB) are promising and illustrate a slow and multiphasic release mechanism at the physiological pH of blood. Therefore, PSS-LDH nanocomposites composed of lower molecular weight polystyrene, at higher levels of sulfonation and end sulfonated PEG, are excellent materials for preparing water-soluble drug delivery systems. We have also determined that 1H NMR spectroscopy can be used as a tool to quickly predict the sequence of d-spacing, crystallinity and stability in a polymer-LOH sample set. The nanocomposites are currently being fabricated using folic acid conjugated PEG for targeted drug delivery in vitro.
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Holding Institution:
Clark Atlanta University
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