Preparation And Characterization Of Cryogel Scaffold Based On Natural Polysaccharides

As the place of cell cultivation and template of tissue regeneration,the three-dimensional porous scaffold is the critical aspect of tissue engineering.An ideal scaffold should have the desired characteristics including open porous structures,a broad pore size distribution,high porosity,good biocompatibility,an appropriate biodegradation rate and adequate mechanical strength.The cryogel matrices prepared through cryo-copolymerization approach meet the most requirements for cell scaffolds,and more and more attention has been paid to their applications in tissue engineering as a sort of novel biomaterials.In this thesis,natural polysaccharides,dextran and hyaluronic acid(a component of extracellular matrix),were used as raw materials to prepare cell scaffolds.The cross-linkable macromonomers were synthesized via modification of dextran and hyaluronic acid with glycidyl methacrylate.The curves of liquid-solid phase transition of macromonomer solutions with various concentrations were measured to determine the corresponding values of freezing point temperature Tmc and the actual initial solvent crystallization temperature Tc at various cooling conditions.A series of dextran/hyaluronic acid composite cryogel scaffolds with mass concentrations of 3%?6%have been prepared under the variation freezing condition.The morphology of the pore structure was observed by SEM and the properties of cryogel scaffolds,such as the porosity,swelling ratio and elastic modulus,were measured.The mouse 3T3-L1 preadipocytes were seeded into the scaffold(5%)and cultured to examine the biocompatibility.The results showed that the modifications of dextran in aprotic solvent DMSO and hyaluronic acid in neutral aqueous were carried out to obtain crosslinkable dextran methacrylates and hyaluronan methacrylate.The degree of substitution of polysaccharide derivates could be controlled by readjusting the ratio of glycidyl methacrylate to polysaccharide.To a certain concentration of polysaccharide derivates macromonomers,the effect of freezing rate on Tmc and Tc could be neglected.Under the same freezing rate,the Tc decreased with the increase in concentration and the Tmc changed little.The obtained cryogel scaffolds were spongy-like,soft and flexible.With the increase of macromonomer mass fraction,the water permeability and swelling ratio of cryogel scaffolds showed a downward tendency,while the elastic modulus increased,which were similar to that of soft tissue.The cryogel scaffolds of 4%and 5%had similar porosities greater than 90%and the mean pore sizes of about 90 ?m.However,obvious decreases of both the porosity and the pore size were observed for the 6%cryogel scaffold.The results of 3T3-L1 preadipocytes cultivation in the scaffold showed that the macroporous cryogel could serve as a good platform for the adhesion,proliferation and penetration of cells and thus was expected to be a potential biomaterial suitable for the development and reconstruction of soft tissue.