Doctor of Philosophy (PhD)
Many amphiphilic molecules (surfactants) possess the ability to aggregate in aqueous solution to form thermodynamically stable aggregates that have potential for use as molecule containers and delivery systems in analytical or pharmaceutical applications. However, it is difficult to release the encapsulated molecules from these aggregates under a controllable manner, and this problem has dramatically limited the application of these aggregated systems. This study addresses this problem through fundamental structure modification by development of a novel redox stimuli-responsive amphiphile capable of forming vesicle aggregates. Aggregate structure can be adjusted through redox stimulation. The release of agents from the core of the aggregates containers can be controlled by the same mechanism. The novel surfactant molecule, Q9 (Figure 1.3), containing a redox stimuli-responsive moiety was synthesized through seven synthetic steps for this purpose (Chapter 3). The molecular structures were characterized by 1H NMR and mass spectrometry analysis methods. Properties of Q9 in aqueous solution were studied (Chapter 4). The pH sensitivity of Q9 was explored in a variety of phosphate-buffered saline (PBS) solutions with UV-vis measurements and 1H NMR experiments; from these studies, suitable pH value was determined for Q9 vesicle formation. The stimuli-responsive mechanism of Q9 was confirmed by 1H NMR kinetic studies. The critical aggregation concentration (CAC) was determined by surface tension measurements. Q9 vesicles were formed by the extrusion technique (Chapter 5). Vesicle characterizations were evaluated using transmission electron microscopy, light scattering, cryo-electron microscopy and asymmetrical flow field-flow fractionation. Q9 vesicles were used to encapsulate the model guest calcein (Chapter 6). Size-exclusion chromatography was used to isolate Q9 vesicles containing dye calcein. The successful release of calcein from Q9 vesicles was triggered by use of a chemical reducing agent as observed by the time-dependent increase in calcein fluorescence. Based on the data, it appears that the loading volume and number density of Q9 vesicles dictates their capabilities as an efficient molecule delivery system.
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Yang, Yuming, "Development of New Stimuli-Responsive Vesicles Using A Novel Surfactant" (2008). LSU Doctoral Dissertations. 4011.
Robin L Mccarley