Huh Kang Moo, Cho Yong Woo, Chung Hesson, Kwon Ick Chan, Jeong Seo Young, Ooya Tooru, Lee Won Kyu, Sasaki Shintaro, Yui Nobuhiko
School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Tatsunokuchi, Ishikawa 923-1292, Japan.
Macromol Biosci. 2004 Feb 20;4(2):92-9. doi: 10.1002/mabi.200300037.
Supramolecular hydrogels have been prepared on the basis of polymer inclusion complex (PIC) formation between poly(ethylene glycol) (PEG)-modified chitosans and alpha-cyclodextrin (alpha-CD). A series of PEG-modified chitosans were synthesized by coupling reactions between chitosan and monocarboxylated PEG using water-soluble carbodiimide (EDC) as coupling agent. With simple mixing, the resultant supramolecular assembly of the polymers and alpha-CD molecules led to hydrogel formation in aqueous media. The supramolecular structure of the PIC hydrogels was confirmed by differential scanning calorimetry (DSC), X-ray diffraction, and (13)C cross-polarized/magic-angle spinning (CP/MAS) NMR characterization. The PEG side-chains on the chitosan backbones were found to form inclusion complexes (ICs) with alpha-CD molecules, resulting in the formation of channel-type crystalline micro-domains. The IC domains play an important role in holding together hydrated chitosan chains as physical junctions. The gelation property was affected by several factors including the PEG content in the polymers, the solution concentration, the mixing ratio of host and guest molecules, temperature, pH, etc. All the hydrogels in acidic conditions exhibited thermo-reversible gel-sol transitions under appropriate conditions of mixing ratio and PEG content in the mixing process. The transitions were induced by supramolecular association and dissociation. These supramolecular hydrogels were found to have phase-separated structures that consist of hydrophobic crystalline PIC domains, which were formed by the host-guest interaction between alpha-CD and PEG, and hydrated chitosan matrices below the pK(a).The formation of inclusion complexes between alpha-cyclodextrin and PEG-modified chitosan leads to the formation of hydrogels that can undergo thermo-reversible supramolecular dissociation.
基于聚乙二醇（PEG）修饰的壳聚糖与α-环糊精（α-CD）之间形成的聚合物包合物（PIC），制备了超分子水凝胶。使用水溶性碳二亚胺（EDC）作为偶联剂，通过壳聚糖与单羧基化PEG之间的偶联反应合成了一系列PEG修饰的壳聚糖。通过简单混合，所得的聚合物和α-CD分子的超分子组装体在水性介质中形成水凝胶。通过差示扫描量热法（DSC）、X射线衍射和（13）C交叉极化/魔角旋转（CP/MAS）NMR表征证实了PIC水凝胶的超分子结构。发现壳聚糖主链上的PEG侧链与α-CD分子形成包合物（ICs），从而形成通道型结晶微区。IC域在将水合壳聚糖链作为物理连接点聚集在一起方面起着重要作用。凝胶化性质受多种因素影响，包括聚合物中的PEG含量、溶液浓度、主体和客体分子的混合比例、温度、pH等。在混合过程中，在适当的混合比例和PEG含量条件下，所有酸性条件下的水凝胶都表现出热可逆的凝胶-溶胶转变。这些转变是由超分子缔合和解离引起的。发现这些超分子水凝胶具有相分离结构，该结构由疏水性结晶PIC域组成，这些域是由α-CD与PEG之间的主客体相互作用形成的，以及低于pK（a）的水合壳聚糖基质。α-环糊精与PEG修饰的壳聚糖之间形成包合物导致形成可经历热可逆超分子解离的水凝胶。
