Porous nerve guidance conduits reinforced with braided composite structures of silk/magnesium filaments for peripheral nerve repair

Abstract

Peripheral nerve repair is a common but challenging surgical treatment. Many artificial nerve grafts have been developed, including nerve guidance conduits (NGCs) with biocompatibility, suitable mechanical properties and topography to guide axon growth. However, there remains a need to promote nerve regeneration and accelerate functional recovery using NGCs for nerve reconstruction. Here, silk fibroin (SF) and magnesium (S/Mg) filaments were braided into an inner layer of NGC and freeze-dried with a solution of SF and chitosan (CS). The mechanical stress of these S/Mg-SF/CS conduits reached 2.8 ± 0.2 N and possessed high compression strength. The conduits were evaluated with subcutaneous implantation. Sustainable mechanical function was demonstrated when used to repair 10 mm sciatic nerve gaps in rats. The hollow NGCs improved neurochemotaxis from the damaged nerves. The wet weight ratio of the gastrocnemius muscle, a target muscle for the sciatic nerve related to motor and sensory functions in the NGC group, reached 83.5% of that in the autologous group in 8 weeks; the nerve ports at both ends of the NGC grew well. When the distal end of the regenerated nerve was observed by Transmission Electron Microscopy (TEM), there was no significance difference in the diameter and thickness of the myelin sheath of the distal nerve between the autograft and S/Mg-SF/CS group, indicating that S/Mg-SF/CS NGC in this study promoted the growth of damaged nerves and provided appropriate physio mechanical guidance, thus suggesting potential utility for this approach in artificial nerve transplantation. Statement of significance1. Porous nerve guidance conduits (NGCs) is reinforced by a braided composite structure consisting of silk/magnesium filaments, which provides the NGC with appropriate physio-mechanical guidance as well as sufficient stability to support the biological micro-environment during early-stages of nerve regeneration and functional recovery.2. Sufficient mechanical properties, biocompatibility with Schwan cells and good performance after sciatic nerve transplantation demonstrates that the S/Mg-SF/CS NGC in this study promotes the growth of damaged nerves and provides a suitable physio-mechanical guide for potential in artificial nerve transplantation.3. A facile scalable manufacturing process is achieved by utilizing multidisciplinary engineering, such as textile technologies, biomaterial engineering and medical science.