Fabrication And Related Properties Of Silk Fibroin/Chitosan Conduits

Peripheral nerve regeneration after injuries remains a challenge to modern medicine due to the complexity of the neurobiological nerve regenerating progress. It’s difficult to repair long gap nerve injuries by surgeries and autologous nerve graft was always the first choice. However, for repairing long gap nerve injuries, autologous nerve graft isn’t the ideal treatment due to the morbidity at donor sites, the limited availability of donor nerve and the mismatched dimensions between the injured nerve and the donated graft. The current trend for long gap peripheral nerve regeneration is to develop multifunctional nerve conduits that can act as physicochemical guidance and biological cues for the regeneration of nerves across lesions.In the present study, chitosan(CS) and silk fibroin(SF) solution were first blended together, and then, the conduits were fabricated by a one-step processing method involving vacuum freeze drying technique. The structures and properties of conduits were controlled by mainly regulating the volume ratio of CS to SF, the concentration of SF/CH mixtures and the freeze conditions. The component proportion and concentration of SF/CH mixtures were optimized by comparing the compressive properties, deformation recovery rates and the in vivo degradability. Anthropogenic normal liver cell HL 7702 cells were cultured with leach liquor of conduits at different concentrations and tested by MTT assay to analyze the cytotoxity of components in the conduits. Furthermore, conduits were co-cultured with the mice adrenal pheochromocytoma cells(PC12 cells), and then environment scanning electron microscope(ESEM) was used to check the cell-conduits interaction.Several kinds of conduits with regular shape were fabricated after freeze dry. The volume ratios of CS to SF were 1:1, 2:1 and 3:1, and the concentration of mixture were 5%, 6% and 7%, respectively. The inner diameter, outer diameter and length of SF/CS conduits were about 3, 6 and 45 mm, respectively, and the porosity of conduits was around 60-70%. In vivo degradation results showed that increasing chitosan amount would increase the degradation rate of conduits and the conduit built with lower concentration of mixtures would degrade faster. At the same CS/SF volume ratio, the compress property and deformation recovery rate of conduits would be better when the concentration of SF/CS mixture for conduit preparation was higher. Based on above results, the conduit constructed with a ratio of CS to SF at 2:1 and with a 6% concentration for the mixture was selected for the biocompatibility assessment. Results obtained from MTT assay and SEM examinations showed that the conduits were nontoxicity and suitable to the growth of cells.In conclusion, the SF/CS conduit shows highly porous structure, and their compressive mechanical properties, in vivo degradability and biocompatibility suggest that some optimal conduits have promising potential for the applications in nerve tissue engineering.