Institute of Polymer Science and Engineering, College of Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei City 10617, Taiwan.
Carbohydr Res. 2011 Jan 3;346(1):94-102. doi: 10.1016/j.carres.2010.10.010. Epub 2010 Oct 20.
In this study, the depolymerization of chitosan was carried out in an acetic acid aqueous solution and was followed by viscometry for molecular weight determination. It was found that the depolymerization rate increased with elevated temperatures and with high acid concentrations. Based on FTIR analysis, the chitosan was depolymerized randomly along the backbone; no other structural change was observed during the acid depolymerization process. Revealed in the TGA study, the degradation temperature and char yield of LMWCs (low molecular weight chitosan) were molecular weight dependent. The blood compatibility of LMWCs was also investigated: rouleaux formation was observed when erythrocyte contacted with LMWCs, which showed that LMWCs are able to interfere with the negatively charged cell membrane through its polycationic properties. Furthermore, as regards a kinetics investigation, the values of M(n) (number-average molecular weight) were obtained from an experimentally determined relationship. The kinetics study showed that the complex salt, formed by amine on chitosan and acetic acid, acted as catalyst. Finally, the activation energy for the hydrolysis of the glycosidic linkage on chitosan was calculated to be 40kJ/mol; the mechanism of acid depolymerization is proposed. In summary, LMWCs could be easily and numerously generated with acid depolymerization for further biological applications.
在这项研究中，壳聚糖在乙酸水溶液中进行解聚，并通过粘度法进行分子量测定。结果发现，解聚速率随温度升高和酸浓度增加而增加。基于傅里叶变换红外（FTIR）分析，壳聚糖沿着主链随机解聚；在酸解聚过程中没有观察到其他结构变化。热重分析（TGA）表明，低分子量壳聚糖（LMWCs）的降解温度和残炭产率与分子量有关。还研究了 LMWCs 的血液相容性：当红细胞与 LMWCs 接触时，观察到红细胞形成缗钱状，这表明 LMWCs 能够通过其聚阳离子特性干扰带负电荷的细胞膜。此外，关于动力学研究，从实验确定的关系中获得了数均分子量（M(n)）的值。动力学研究表明，壳聚糖上的氨基与乙酸形成的复合盐充当催化剂。最后，计算出壳聚糖糖苷键水解的活化能为 40kJ/mol；提出了酸解聚的机理。总之，可以通过酸解聚轻松且大量地生成 LMWCs，用于进一步的生物学应用。
