壳聚糖的烷基化修饰及其对凝血性能的影响

Uncontrolled hemorrhage is the leading cause of death in trauma. Chitosan can speed blood coagulation since its active amine and hydroxyl groups which could absorb blood plasma proteins, adhere with erythrocytes, aggregate and activate platelets. However, recent studies indicated that the hemostatic effect of chitosan on serious bleeding wounds was very limited. So how to improve the blood coagulating property of chitosan by molecular design and chemical modification remains a major problem to material scientists..In this study, chitosan with middle molecular weight is chosen as raw material, a series of N-alkyl chitosan derivations with different substitution degrees will be synthesized by reductive amination reaction. The research focus includes: how the structure parameters of N-alkyl chitosan and their concentrations affect their rheological property in blood components and their aggregation behaviour in aqueous solution, whether the gel-forming ability of modified chitosan- blood mixtures is related to their aggregation property, the clotting property of N-alkyl chitosan, the effects of modified chitosan on plasma proteins, erythrocytes and platelets, and their clotting mechanism. .By above study, the main factors influencing the clotting property of alkyl chitosan could be obtained, based on which, an excellent chitosan-based hemostat might be provided to clinic in near future. Furthermore, the research level on functional design of chitosan and its biological effects might be improved as well.

过度失血是创伤致死的主要原因。壳聚糖含有活性氨基和羟基，能吸附血浆蛋白、粘附红细胞、激活血小板，因而具有加速凝血作用，但壳聚糖的止血效果还很有限。如何通过分子设计和化学改性，提高其凝血性是亟待解决的难题。本项目拟通过还原胺化反应在壳聚糖主链上接枝一定数量、不同碳链长度的烷基基团，制备出N-烷基壳聚糖；研究N-烷基壳聚糖的结构参数与浓度对材料-血液体系流变性能的影响，分析影响材料-血液相互作用形成凝胶的主要因素；研究改性壳聚糖的结构参数与浓度对其在水溶液中自组装聚集行为的影响，分析其血液流变性与溶液聚集行为的相关性；研究N-烷基壳聚糖的凝血性能及其对血浆蛋白的特异性吸附与活化、对红细胞的粘附与聚集、以及对血小板的活化效应，探讨其凝血机制。通过上述研究，不仅可以获得影响烷基化修饰壳聚糖凝血性能的主要因素，为其临床应用奠定基础，而且也会推动壳聚糖的功能化设计及其在生物学效应方面的研究水平。

过度失血是创伤致死的主要原因。壳聚糖含有活性氨基和羟基，能吸附血浆蛋白、粘附红细胞、激活血小板，具有加速凝血作用，但其凝血效果比较有限。如何通过分子设计和化学改性，提高其凝血性是亟待解决的难题。本项目通过还原胺化反应在壳聚糖主链上接枝一定数量（取代度为：<10% 、10-20% 、30-40%）、不同碳链长度（6、12、18）的烷基基团，制备出系列N-烷基壳聚糖；研究了N-烷基壳聚糖取代度对材料-血液体系流变性能的影响；N-烷基壳聚糖的结构参数对其在水溶液中自组装聚集行为的影响；N-烷基壳聚糖的凝血性能及其对红细胞、血小板的粘附、聚集与活化效应，探讨其凝血机制。研究发现：壳聚糖分子量为98KDW时，取代度为35.44%的N-十八烷基壳聚糖粉末的全血凝固时间最短（30s）；壳聚糖分子量为560KDW时，接枝了32.69%的N-十二烷基壳聚糖海绵的全血凝固时间最短（68s)；壳聚糖分子量为1970KDW时，取代度为8.98%的N-十八烷基壳聚糖纳米纤维膜的全血凝固时间最短(83s)。研究表明：同壳聚糖相比，N-烷基壳聚糖能够显著提升材料的凝血性能，其体外凝血性能与接枝烷基的碳链长度、烷基取代度、壳聚糖分子量以及材料的物理状态相关。流变学研究表明：壳聚糖、N-烷基壳聚糖与全血混合后呈现物理凝胶弹性响应特征，且N-烷基壳聚糖的G′/G″大于壳聚糖原样，其G′/G″随己烷取代度的升高而增大，与N-烷基壳聚糖体外凝血性能一致。对N-烷基壳聚糖在水溶液中自组装聚集行为的研究发现：与纯壳聚糖相比，N-烷基壳聚糖的CAC明显减小；烷基链长相同时，烷基链的取代度越大，CAC值越小；接枝烷基的取代度相同时，烷基链越长，CAC值越小。N-烷基壳聚糖促进凝血作用的因素包括：（1）吸附血浆，聚集血细胞；（2）粘附、活化血小板；（3）聚集、活化红细胞；（4）烷基基团自组装为胶束并嵌入血细胞磷脂双分子层，有利于网络血细胞，形成血栓凝胶。