Yeh Hsi-Yi, Lin Jui-Che
Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan, ROC.
J Biomater Sci Polym Ed. 2008;19(3):291-310. doi: 10.1163/156856208783720985.
Glycosaminoglycans (GAGs) are the main components of the extracellular matrix (ECM). Studies have indicated that scaffolds modified by GAGs could improve cell proliferation and differentiation. Chitosan, the second-most abundant nature polysaccharide, has a structure similar to that of GAGs. Due to its relatively lower cost as compared to GAGs, many researchers have tried to incorporate sulfonate or carboxyl groups into the chitosan structure with the aim to form a GAG-like structure. However, these modifications were carried out on the reactive amino groups that were thought as the major character, resulting in special biological properties associated with chitosan. Such a decrease of amino-functional group density would very likely alter the specific biological properties of chitosan. Therefore, an amino group protection-deprotection strategy was explored in this study for surface sulfonation of chitosan membrane with the aim to imitate GAG structures. Various surface chemical characterization results, as well as surface zeta potential measurements have indicated that both sulfonate/sulfonic and amino functionalities were coexistent on the deprotected sulfonated chitosan specimen. In vitro platelet adhesion testing has shown that such a deprotected sulfonated chitosan membrane can increase the amount of platelet adhesion while keep those adhered remained unactivated. At the same time the presence of deprotected sulfonated chitosan film extended the plasma recalcification time value. With this protection-deprotection strategy, a further chemical grafting of bioactive molecules, such as RGD peptide, using the recovered amino functionalities, can be pursued on these sulfonated chitosan specimens.
糖胺聚糖（GAGs）是细胞外基质（ECM）的主要成分。研究表明，经GAGs修饰的支架可促进细胞增殖和分化。壳聚糖是自然界中含量第二丰富的多糖，其结构与GAGs相似。由于与GAGs相比成本相对较低，许多研究人员试图将磺酸基或羧基引入壳聚糖结构中，以形成类似GAG的结构。然而，这些修饰是在被认为是主要特征的活性氨基上进行的，导致了与壳聚糖相关的特殊生物学特性。这种氨基官能团密度的降低很可能会改变壳聚糖的特定生物学特性。因此，本研究探索了一种氨基保护-脱保护策略，用于壳聚糖膜的表面磺化，以模仿GAG结构。各种表面化学表征结果以及表面zeta电位测量表明，脱保护的磺化壳聚糖样品上同时存在磺酸根/磺酸基和氨基官能团。体外血小板粘附试验表明，这种脱保护的磺化壳聚糖膜可以增加血小板的粘附量，同时使粘附的血小板保持未激活状态。同时，脱保护的磺化壳聚糖膜的存在延长了血浆复钙时间值。采用这种保护-脱保护策略，可以利用回收的氨基官能团在这些磺化壳聚糖样品上进一步化学接枝生物活性分子，如RGD肽。
