| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 100 === In this study, the ion pair amphiphiles (IPAs), hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS) and dodecyltrimethylammonium-dodecylsulfate (DTMA-DS), were prepared by mixing aqueous solutions of the cationic surfactants, hexadecyltrimethylammonium bromide (HTMAB) and dodecyltrimethylammonium bromide (DTMAB), respectively, with the anionic surfactant, sodium dodecylsulfate (SDS). HTMA-DS and DTMA-DS were then used as the main materials, respectively, with the addition of various molar fractions of dialkyldimethylammonium bromide (DXDAB) to form positively charged catanionic vesicles by an appropriate process. When the molar fraction of DXDAB (XDXDAB) was 0.5, the vesicles composed of HTMA-DS/DHDAB and DTMA-DS/DHDAB possessed better physical stability. Since the alkyl chain length of DHDAB is between those of DODAB and DTDAB, it is proposed that the vesicle physical stability was related to not only the van der Waals interaction between IPA and DXDAB, but also the symmetry of the hydrocarbon chains of the vesicle-forming materials.
For the vesicle systems with the addition of bovine serum albumin (BSA), the adsorption of BSA on the vesicles could decrease the zeta potential of the vesicles, and charge reversal of the vesicles was observed at high BSA concentrations. From the IR spectrum analysis, one could find that the insertion of the hydrophobic groups of BSA into the vesicular bilayers was related to the interaction between IPA and DXDAB. The strong interaction between IPA and DHDAB caused the difficulty for the hydrophobic groups of BSA to insert into the vesicular bilayers composed of HTMA-DS/DHDAB and DTMA-DS/DHDAB. Without the charge reversal of the vesicles, the reduced zeta potential of the vesicles due to the BSA adsorption and the insertion of the BSA hydrophobic groups into the vesicular bilayers would lower the physical stability of the vesicles. Nevertheless, with the charge reversal of the vesicles, more BSA adsorbing onto the vesicles could enhance the physical stability of the vesicles. The addition of cholesterol was also tried in this study to improve the vesicle physical stability, and it was found that cholesterol could increase the zeta potential of the vesicles and adjust the packing characteristic of the molecular hydrocarbon chains in the vesicular bilayers, resulting in enhanced physical stability of the vesicles. The addition of cholesterol could also prevent the vesicles from BSA-induced aggregation and fusion and thus increase the vesicle physical stability.
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