Preparation And Material Properties Of Nerve Conduit With A Tube In Tube Structure

In recent years, with the increasing in the incidence of nerve injury, nerve graft could not satisfied the nerve regeneration for the restrictions of distance and defect in donor’s functions. So the restoration, regeneration and functional recovery in nerve injury have become a primary research direction in neuroscience and the nerve conduit is put forward. The nerve conduit is the connection of fracture nerves to provide suitable microenvironment for nerve growth and the idea conduit can also provide orientation for proliferation of nerve cells. In this paper, a novel nerve conduit with a tube in tube structure was designed and detailed experimental studies of fundamental properties were made. In addition, technical feasibility and reasonableness of the method were also discussed based on the results, and expected to bring the nerve conduit closer to being a realistic possibility.Nanofibrous scaffolds, prepared by electrospinning with high porosity and large surface area, could imitate the natural extracellular matrix in the nano-scale, so it can be used as a porous scaffold to promote cell migration and proliferation in tissue engineering, wound dressing and pharmaceutical carriers. In this paper, the outward scaffolds were prepared by electrospinning and aligned nano-fibers that obtained by optimizing the spinning parameters and receiving apparatus could promote the cells’migration and proliferation. What’s more, wet spinning was an effective method to prepare continuous hollow fibers, so inside hollow fibers were gained by this method.Poly(butylene carbonate)(PBC), chitin nano-whiskers (ChW), high-density chitosan (HCS) and functionalized multi-walled carbon nanotubes (f-MWNTs) were chosen as the basic materials for scaffolds. Through the improvement of electrospinning technology, materials composition and surface modification, the mechanical properties, cell compatibility and degradation rate were also deeply studied. Main researches are listed as follows:1. Random nano-fibers and aligned nano-fibers were prepared by electrospinning and the relationship of rotating speed of the receiving instrument and the basic performance of nano-fibers were discussed in detail. After plasma pretreatment and gelatin graft, hydrophilicity and biocompatibility of the aligned fiber mats could be improved significantly. Studies show that PBC could dissolve in some organic solvent such as formic acid (FA), dimethylformamide (DMF), hexafluoroisopropanol (HFIP) and chloroform, but the uniform and smooth fibers could only obtain from the FA solution; During the process of preparing aligned PBC nano-fibers, the order degree of fibers, the crystallinity and the orientation of crystalline region including mechanical strength are all increased correspondingly with the increment of rotating speed.2. Chitin nano-whiskers made by acid decomposition method were added into PBC solutions to obtain compound nano-fibers in order to improve mechanical properties. The studies found that, the length and diameter of ChW were in the range of180-680nm and15-30nm respectively and the average length diameter ratio was14.7. In addition, the morphology of ChW in FA solvent was not changed and this has provided basis for the further experiment. The nano-fibers with uniform diameter distribution and smooth surface could be prepared with the addition of ChW up to5.0wt%; the crystallinity, thermal stability and mechanical properties are increased correspondingly with the increasing of ChW contents. After plasma pretreatment, hydrophilicity of the aligned fiber mats was improved significantly, and the fiber mats was then immersed into gelatin solution for grafting. The aligned nano-fibers after gelatin grafting could stimulate the adhesion and proliferation of RSC96cells.3. In the paper, the spinning solutions were prepared by using acetic acid as solvent; the rheology of the solutions were studied to investigate the effect of the solid content and the spinning temperature on the stability of the spinning solutions and the spinning process. Then hollow fibers were obtained by the method of wet spinning and chemical structures, crystal structures, thermal properties including mechanical property were researched. The results showed that:we could obtain hollow fibers smoothly with the concentration of the spinning solution in5wt%at20-30℃the fibers had excellent properties that regenerated within the coagulation bath of3wt%sodium hydroxide-ethanol (mass ratio of1:1).4. The dispersivity and compatibility with HCS of f-MWNTs that obtained via a controlled surface deposition and crosslinking process have been improved a lot; most of the tube body spread out that close to single dispersion, and the tangle also was eased after deposition and crosslinking process. The hollow fibers with the f-MWNTs content of0.5wt%exhibit the optimal tensile property with the maximum tensile strength and elasticity modulus of9.33MPa and2.34GPa, respectively. The fiber was then immersed into gelatin solution for grafting after pretreatment. Under the condition of same moisture content, the conductivity of composite hollow fibers was also improved with the increase of the content of f-MWNTs. XPS results also showed that some oxygen element was introduced to the surface of the pretreated samples for subsequently exposing to air (atomic fraction rising from29.07%to38.28%); in following grafting reaction, the active groups from gelatin introduce a large amount of nitrogen (from1.73%to7.54%) and the C-C bond broke down to form C=O and C=N bonds or other polar groups to realize the grafting reaction. Form biological characterization such as cell attachment, cell morphology and proliferation, these results demonstrate following two aspects. First, the addition of a small amount of f-MWNTs in fibers with the cell adhesion rate of77.44%which equal to HCS fibers (78.29%) after24h have no affect on cell behavior; second, cells seeded in fibers grafted with gelatin have higher adhesion rate and cells can proliferate faster in the same time which proved that the superior ability of fibers after surface modification with gelatin can well support Schwann cells (RSC96) growth and proliferation.5. The aligned nano-fibers prepared from electrospinning was rolled on the core bar with right diameter to form the outer tube of nerve conduit, and then hollow fibers were filled into the tube to receive the nerve conduit with a tube in tube structure. The results of compression properties of nerve conduit indicated that the load force of5-channel conduit could reach up to210cN with the deformation of25%, so the conduit could meet the requirements of the supporting force of nerve regeneration.