Study On The Preparation And Characterization Of Novel Functional Silk Fibroin Hydrogels

Many people suffer from tissue and organ defects and lesions, which are caused by unexpected accidents and diseases. The most effective clinical strategy for solving the problems is transplantation. However the lack of the transplantation tissues remains a big problem. Therefore, more effective methods are required for repairing the tissues in regenerative medicine field. Silk fibroin(SF) has good biocompatibility, biodegradability, excellent mechanical properties and regeneration capacity, making it promising as scaffolds for various tissue engineering. Recently, SF-based hydrogel is becoming a hot spot in tissue regeneration.Unlike the silk solutions prepared with lithium bromide as solvent, here, we prepared silk nanofiber solution through tuning solvent system firstly. The silk nanofibers are mainly composed of amorphous structures, providing a reliable unit for the fabrication of silk fibroin nanofiber hydrogel.Silk nanofiber solutions were concentrated with PEG to prepare silk fibroin hydrogel with tunable mechanical properties. Through covalently crosslinking tyrosine residues in silk nanofibers via horseradish peroxidase and hydrogen peroxide, hydrogels with tunable properties formed. The influence of the concention of silk nanofiber, HRP and H2O2 in the reaction system on the the geltime, secondary structure, nano-structure and mechanical properties of the formed hydrogel were elucidated. It was found that the secondary structures remained stable after gel formation, keeping amorphous states. The mechanical properties of the formed hydrogel could be regulated in the range from 600 Pa to 20 kPa through tuning silk concentration, as well as HRP and H2O2 ratios. It suggests that it is possible to satisfy the mechanical requirements of various tissues.. Therefore, HRP crosslinked silk hydrogels with nanofibrous structures and tunable mechanical properties are developed through controlling silk nanostructures.Then, silk nanofibers with high beta sheet content and higher negative charge density were used to further tune the mechanical properties of the HRP crosslinked hydrogels. The silk nanofibers with high beta sheet content were blended with amorphous silk nanofibers at different proportions and then crosslinked with HRP under an electric field.The mechanical properties of the hydrogel near the positive electrode increased to 500 kPa while that near the negative electrode was about 200 kPa. The mechanical properties could also be regulated through changing the ratios of the two nanofibers and the treated time in the electric field.In summary, silk hydrogels with tunable performances were prepared through the modified HRP crosslinking method. The tunable properties of these hydrogles suggest their promising applications as the scaffolds for various tissue regenerations.