Preparation Of Electrospun SF-based Scaffolds And Application In Nerve Repair

Nanoscale polymeric fibrous materials are the fundamental building unit of live systems. For example, the diameter of double helix DNA molecules is 2 nm, and the cytoskeleton filament is 30 nm. Nano-scale fibrous materials are consistency in the aspect of microstructure with the extracellular matrix (ECM). To date, many distinct techniques have proved successful in preparing nanoscale fibrous materials, such as self-assembly, phase separation, template method etc; however, electrospinning is considered to be more likely to achieve continuous and mass production of nano-fiber material. Polymer can be electrospun to produce nanofibers of with diameters as small as 3 nm, and the 3 nm diameter fibers have only 6 or 7 molecules across the fiber.In recent years, there has been significant increasing interest in the utilization of natural materials for novel nano-products, such as silk fibroin nanofibrous tissue engineered scaffolds. Silkworm silk, a protein-base natural biopolymer, has received keen interest in various areas due to its unique properties (strength, biocompatibility) and vast potential applications such as smart textiles, protective clothing, filter materials, sustained-release material and tissue engineering, especially in the field of tissue engineering has become the hot spot.This research deals with fabrication of tissue scaffolds from Bombyx mori silk fibroin (BSF) and Tussah silk fibroin (TSF) for its abundant supply and excellent mechanical and biological property. The purpose of this study is to prepare silk fibroin (SF)-based nanofibrous scaffold, determine the property of electrospun silk fibroin nanofibers; to study the biocompatibility with nerve cells (neuron, neural stem cell (NSCs), Olfactory ensheathing cells (OECs), Schwann cells (SCs)), and to bridge 10-mm sciatic nerve defects of rats with silk fibroin-based artificial nerve tube.The BSF/TSF blends nanofibers were prepared by electrospinning with the solvent of HFIP, and the average diameters of BSF/TSF blend fibers increased from 404 to 1977nm, with the increase of BSF content in blend solutions, and the relationship between the average diameters of BSF/TSF and BSF content was proved to be linear correlation. Results from FTIR, TG-DTA and X-ray diffraction showed BSF and TSF were still immiscible even dissolved in hexafluoroisopropanol (HFIP) after electrospinning and ethanol treatment.Methanol, ethanol, isopropanol and different aqueous ethanol solution all were proved effective in inducing conformation transition of BSF nanofibers, it suggested that the material morphology, initial structure, crystalline structure determine if the conformation transition of silk fibroin when immersion in organic solution, and hydrophobic interaction is the driving force of structural change. The two methods of addition of EDC in electrospin solution, or EDC/NHS ethanol system were effective in improving mechanical integrity and stability.Analysis of the morphology and number of nerve cells cultured on silk fibroin nanofibers indicated that cell adhesive, complexity, and proliferation was more obvious on TSF and BSF nanofibers, importantly, cell gather to form büngner band which is important for nerve regeneration.SF nanofiber-based artificial nerve conduits were prepared by electrospinning and applied to bridge 10mm long sciatic nerve defect of rats. The present study shows that the electrospun silk fibroin tubes are successful in bridging a 10mm gap in the sciatic nerve of the rat, especially TSF tubes demonstrated a superior repair results.