Preparation And Blood Compatibility Of Sulfonated 6-Carboxy Chitosan

Chitosan is a nature polysaccharide having similar structure with cellulose. Because of its polycation electrolyte characteristics, chitosan could easily adsorb erythrocytes and thrombocytes, which carried negative charges on the surface, to form thrombus or cause hemolysis when it contacted with blood. In this paper, the microfibers inβ-chitosan sample were observed for the first time. In addition, chitosan was oxidized to 6-carboxychitosan; further more, sulfo groups were grafted on it in formamide medium to give sulfated 6-carboxylchitosan. The structures, properties and blood compatibilities of 6-carboxychitosan and sulfated 6-carboxylchitosan were studied.By dispersing porous chitosan powder in glacial acetic acid, the hydroxymethyl groups of chitosan were successively oxidized to carboxyl groups with NO2 gas to form 6-carboxychitosan. Because glacial acetic acid could soak into porous chitosan powder and absorbed the water produced in the oxidization process, not only the degree of oxidization (DO) of hydroxymethyl groups in 6-carboxychitosan might reach to 47%, much higher than did in other mediums such as tetrachloromethane, water etc, but also the oxidative degradation reaction of chitosan could be weakened obviously. The 6-carboxychitosan has the common characteristics of an amphoteric polyelectrolyte, When the DO and degree of deacetylation of 6-carboxychitosan was 37% and 85%, respectively, the isoelectric point (pI) value of 6-carboxychitosan is 4.9. All antithrombosis test, hemolysis test, and blood cell morphology observation with SEM revealed that 6-carboxychitosan had superior blood compatibility to chitosan. By dipping chitosan films in saturated NO2-glacial acetic acid solution, the hydromethyl groups on the film surface could be oxidized to carboxyl groups without decreasing obviously tensile strength of the films. The blood compatibilities of the modified chitosan films were superior to chitosan ones. By crosslinking 6-carboxy-chitosan with glutaraldehyde, 6-carboxy-chitosan spheres were obtained. 6-Carboxy-chitosan spheres, having no adsorption for albumin, were good adsorbent for some uremic toxins such as uric acid, hippuric acid, etc.6-Carboxychitosan was sulfated with chlorosulfonic acid in formamide to give sulfated 6-carboxylchitosan. In sulfated 6-carboxylchitosan, -SO3H groups were primarily grafted on–NH2, next on secondary–OH, and thirdly on–CH2OH positions. With the content of sulfur in sodium salt of sulfated 6-carboxylchitosan increased, the anticoagulation activity of it increased slowly when the content not more than 4.2%, and rapidly when the content more than 4.2%. When the content of sulfur in sodium salt of sulfated 6-carboxylchitosan was 10.5%, the anticoagulation activity of it was similar with heparin sodium (The content of sulfur was 10.1%). The sodium salt of sulfated 6-carboxylchitosan was more similar with heparin sodium than sodium salt of sulfated chitosan did in both structure and anticoagulation activity.