Preparation And Study Of Galactosylated Chitosan Polymer Biomaterials Of Liver Tissue Engineering

Liver is one of the most important and complex organs, serving several indispensable functions such as metabolism, elimination of toxicant, regulation of circulation in the body. Currently, many patients with liver failure are suffering from loss of liver functions. So the research of optimal liver scaffold became the urgent task of medicine and biological material fields. Chitosan as a binary heteropolysaccharide containing linked 2-acetamide-2-β-D-glucopyranose and 2-amino-2-deoxy-β-D-glucopyranose residues has characteristic similar to glycosaminoglycans and is biodegradable and non-toxic. The chitosan molecule has amino and hydroxyl groups which can be modified chemically. Hepatocytes are anchorage-dependent cells on which surfaces asialoglycoprotein receptors exist, however galactose is known as a specific adhesive ligand to asialoglycoprotein receptor (ASGR) of hepatocyte. The introduce of the galactose residues could strengthen the anchorage site within the scaffold and promote the specific cell interactions and various cell fuctions including migration, proliferation, and specific gene expression. Hepatocyte in vivo grows in the three dimensions and cross-link network composed of various ECMs and in vitro this anchorage-dependent cells must adhere to materials to grow and metabolism.So from the point of view of improving chemical structure of materials and geometry size,we mimic the vivo three-dimension environment and prepare the porous galactosylated chitosan scaffold to culture hepatocyte for promoting the culture density and the metabolic activation.In this paper, the porous galactosylated chitosan was synthesized by the reaction the amino group of chitosan and of carboxyl group of lactobionic acid under activiation of EDC and NHS; freeze-drying technique. The structure and physical behaviors were characterized by FT-IR,~1HNMR DSC, XRD, water contact angle and the morphology and properities were analysed. The results confirm the introduction of galatose in the position of 2-NH2 of chitosan and that after the modification of chitosan,because of the decline of hydrogen bond capacity, their degree of crystallinty and thermal stability reduce. Three-dimensional galactosylated chitosan scaffolds for tissue engineering were fabricated by freezing and lyophilizing methods.The physicochemical properties and the biocompatibility of mimic three-dimensional scaffolds were studied and the hepatocytes were cultured in galactosylated chitosan scaffolds. The results shows that the pore diameters under the cool temperature of-20℃and-70℃ranges from 30um to 200um however the pore diameters under the cool temperature of-197℃ranges from 10um-30um,the porous scaffolds which prepared under different temprature have different porosity, water absorption rate, retention rate, compressive strength. The cell proliferation capcity of galactosylated chitosan scaffolds was stronger than chitosan scaffolds and the galactosylated chitosan scaffold don't exist the hemolysis phenomenon.The co-culture of hepatocyte and galactosylated chitosan scaffolds showed that because of the introduce of galactose residue, the hepatocyte density and metabolic activity were greatly improved.