碩士 / 中山醫學大學 / 應用化學系碩士班 / 102 / Alginate(Alg)，which is commonly isolated from brown algae，is an anionic linear polysaccharide composed of two saccharides: epimeric β-D-mannuronate (M) and α-L-guluronate (G). The M and G monomers are covalently bonded through 1,4-glycosidic linkages and arranged into either homopolymeric blocks (MM and GG) or alternating blocks (MGMG) along the polymeric backbone. According to the “egg-box” model，two facing GG blocks can be coordinated with divalent Ca2+ ions, resulting in interchain crosslinking and hydrogel formation，especially rich in GG blocks can incorporate more ionic interactions between chains and usually form a gel with high mechanical integrity.
We developed a photoresponsive hybrid alginate semi-IPN that contains crosslinked β-Cyclodextrin-grafted alginate (β-CD-Alg) and interpenetrating diazobenzene-terminated poly(ethylene glycol) (Az-PEG)，because of the size and shape of the CD cavity，trans-Az and β-CD can form a favorable inclusion complex through host-guest affinity，whereas cis-Az is excluded from the complexation. Therefore，the hybrid gel network features Ca2+ ions as cross-linkers as well as numerous junction points composed of β-CD and trans-Az inclusion complexes.
Moreover，UV light irradiation induces efficient trans-to-cis isomerization. Accordingly，the hybrid alginate hydrogel is sensitive to the UV light used to facilitate trans-to-cis photoisomerization，which results in the dissociation of the inclusion complex and partial gel degradation. Thus，a light trigger can accelerate the release rate of small molecules entrapped within the gel. In addition to causing spontaneous drug release during gel swelling, this strategy entails using a bulk alginate hydrogel as a photocontrollable release system.
In conclusion，we demonstrated a smart hybrid alginate hydrogel from which entrapped small molecules were rapidly released through UV light irradiation. The hybrid gel was prepared based on a semi-IPN structure composed of a crosslinked β-CD-grafted alginate and interpenetrating Az-PEG. In addition to crosslinking with the carboxylates along the alginate backbone induced by Ca2+ ions, the additional junctions formed by the host-guest complex between β-CD and trans-Az provided multiple photoresponsive sites within the bulk gel system. UV light irradiation induced efficient trans-to-cis photoisomerization，leading to the dissociation of the cis-Az from β-CD. Moreover，this photosensitive behavior was accompanied by substantial structural degradation of the hybrid gel，enabling the rapid release of entrapped molecules. Because biocompatible alginate hydrogels are widely applied in tissue engineering, in vitro and in vivo biological study of the applications of this photoresponsive hybrid gel in wound healing is currently being conducted.
| Identifer | oai:union.ndltd.org:TW/102CSMU5537001 |
| Date | January 2014 |
| Creators | Chieh-Ying Chiang, 江倢瑩 |
| Contributors | Chih-Chien Chu, 朱智謙 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 104 |
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