Polymer Vesicles Self-Assembling fromOctadecanol Modified Dextrans in AqueousSolutions

• Main Authors: Yun-Chiao Huang, 黃筠喬
• Other Authors: Hsin-Cheng Chiu
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/05440894295238689956

碩士 === 國立中興大學 === 化學工程學系所 === 97 === In this work, the biodegradable amphiphilic dextran-based copolymers comprising of different octadecanol contents are obtained by partial transesterification of activated octadecanol with dextran segments. The chemical compositions of copolymers are determined exactly by 1H-NMR and FT-IR measurements. A series of copolymers is utilized further to prepare polymeric vesicles by two approaches. These nano-scale polymeric assemblies are attained by self-assembly of amphiphilic copolymers in DMSO/H2O co-solvents and then dialysis against water. Combining the results of 1H-NMR and dynamic light scattering (DLS) measurements,the polymeric assemblies can be controlled well by adjusting the DMSO/H2O ratio used during self-assembly of copolymers. Importantly, the Rg/Rh ratios of the above polymeric assemblies examined by static light scattering (SLS) are approximately 1.0,confirming strongly that the structure of assemblies is presented in vesicle-like form.Moreover, the transmission electron microscopy (TEM) images show that thehydrophilic calcein molecules can be confined within the interior aqueous compartment of polymeric vesicles. On the other hand, the micro-scale polymeric vesicles with ca. 1~27μm in size can be obtained by double emulsion (W1/O/W2) process. Increasing the DMSO content of the DMSO/CHCl3 co-solvent reduces the vesicle size .Furthermore, elevating the ionic concentration in the W1 phase not only stabilizes efficiently the vesicle structure but also enlarges the vesicle size. From the data of fluorescence experiments, the small calcein probes can freely transport across the vesicular membrane, whereas the large FITC-dextran (Mw 4000 or 10000 g/mol) molecules within the aqueous compartment of vesicles are incapable of diffusing into outside aqueous phase. For expanding the applications of polymeric vesicles in drug delivery system, the multivesicle assemblies can be obtained further by suspending small vesicles (prepared in the first stage) in the W1 phase of the second-stage double emulsion process that was used to produce large vesicles.