Design Of 3-D Bioactive Porous Scaffolds For Liver Tissue Engineering

Today, liver transplantation is still the only curative treatment for end-stages liver failure. Donor organ shortage, high cost and the need of immunosuppressive medications are still the major limitations in the field of liver transplantation. Thus, alternative innovative cell-based liver directed therapies, liver tissue engineering, are under investigation with the aim, in future an artificial liver tissue could be created and be used for the replacement of the liver function in patients.Following the development of tissue engineering, one strategy for liver tissue engineering is to induce liver tissue regeneration at damaged organ with either transplanted cells or host cells. This cell induced tissue regeneration is achieved by providing a local environment which enables cells to promote proliferation and differentiation. It has been recognized that the environment is naturally composed of biological signal molecules, extracellular matrix molecules, mechanical stress, and cell-cell interactions. Thus,"bioactive"scaffold with an appropriate combination of the biological cues may modify cell activities for tissue regeneration.In this study, our efforts have been focused on the design of hepatocyte-specific three-dimensional bioactive scaffolds used in the culture of hepatocytes for biomimicing the microenvirenment in vitro, and then enhancing the liver functions of the BAL systems.Galactose moieties were covalently coupled with hyaluronic acid through ethylenediamine. The characteristics of gal-hyaluronate were investigated by FT-IR, elemental analysis and XPS. Galactosylated hyaluronic acid-chitosan scaffolds were prepared by lyophilization. The characteristics of the scaffolds were investigated, such as morphology, hydrophilicity, and mechanical properties. In addition, we investigated the hepatocytes adhesion and the morphology of cells in the scaffolds. The hepatocyte-specific functions were also detected. The results indicated that the supplement of galactosylated hyaluronic acid in chitosan network improved the hydrophilicity and mechanical properties of the scaffolds obtained, and improved the adhesion between hepatocytes and scaffolds, enhanced the liver functions and promoted the tissue-like structure formation.The heparin was bound on chitosan-galactosylated hyaluronic acid scaffold by physical adsorption or chemical crosslinking methods to prepare a complex scaffold of chitosan, galactosylated hyaluronic acid and heparin. The composition scaffolds were characterized by FTIR, SEM and XPS. The amount of heparin bount and released from the complex scaffold was measured by toluidine blue method. Then we incorporated EGF into the complex sponge scaffold by simple dipping method and the release amount of EGF was tested by ELISA. So we developed a new complex porous control release system which can control release EGF for liver tissue engineering.As growth factors have short half-lives and easy to denature during preparation, we intended to design and fabricate porous polysaccharide 3D scaffolds carrying plasmid DNA encoding growth factor and non-viral gene vector polyethylenimine. We optimized the gene transfer conditions of PEI/DNA, and investigated the particles size and zeta potential of complexes. Finally the transfection differences between chitosan and alginate scaffolds were detected.