Silk Fibroin/Chitosan Scaffold For Liver Tissue Engineering

Both silk fibroin (SF) and chitosan (CS) are natural biomaterials with good biocompatibility and abundant resource. It is difficult to prepare pure SF scaffold with porous structure, and the anticoagulant property of SF is poor. Meanwhile, pure CS scaffold degradates relatively quickly, and is not stable in aqueous solution. In this study, aiming to improve the physicochemical properties, we prepared the blend of SF and CS as a water-stable scaffold through intense hydrogen bonding, which may be suitable for liver tissue engineering.After freeze-drying, pure SF scaffold demonstrated sheet-like structure. Through controlling the temperature, concentration and mixing time, three-dimensional homogeneous porous silk fibroin/chitosan (SFCS) scaffolds were successfully prepared by freeze-drying method. Adding of CS promoted the conformation transition of SF from a random coil/α-helix to aβ-sheet structure. Furthermore, higher content of CS promoted the formation of moreβ-sheet structure. A model about the self-assembly of SF and CS into three-dimensional porous structure has been proposed.To test the degradation and water-stable properties, in vitro degradation behaviors of SFCS scaffolds have been systematically investigated up to 8 weeks. SFCS scaffolds could maintain its porous structure till 6 weeks of degradation, the degradation rate was relatively stable, the pH value of degradation solution fluctuated in a narrow range near neutrality, and the swelling properties kept steady. SFCS scaffolds demonstrated good cytocompatibility and histocompatibility.SFCS scaffolds could promote the survival and attachment of HepG2 (human hepatoma cell line) cells and primary hepatocytes. They could provide an open-environment to cells with sufficient nutrition and gas exchange and promote their ingrowth. The in vivo implantation of porous SFCS scaffolds into subcutaneous tissue and omentum of SD rats resulted in slight inflammation and moderate degradation rate. SFCS scaffolds could maintain porous structure after 4 weeks of implantation. Heparin was added into SFCS scaffolds under mild conditions. SFCS scaffolds containing heparin maintained porous structure, good hydrophilicity and mechanical properties, moreover, they were not cytotoxic. Adding of heparin leads the SFCS scaffold to be blood compatible and an effective heparin delivering system for liver tissue engineering.