Surface characterization and in vitro platelet compatibility study of surface sulfonated chitosan membrane with amino group protection-deprotection strategy

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.