Evaluations And Effects Of Porosity On Braided Nerve Regeneration Conduits

Peripheral nerve defect continues to be one of the main problems in plastics which calls for massive implants for nerve reparation, including autologous, allogenous and artificial implants. However, grafting is restricted by many drawbacks, such as the lack of source, donor site morbidity and immunological rejection. Tissue engineering has developed rapidly in recent years and brought new great opportunities for nerve regeneration.The structure and architecture are two elements that affect the functions of nerve regeneration conduit and play key role in its eventual application.Pore is an essential part of the scaffold, which can be evaluated with pore size, pore shape and distribution and porosity. A peripheral nerve conduit should possess 3-D porous solid structure, high porosity and high surface area to volume ratio so as to provide an ideal environment for the regeneration of peripheral nerve. Porosity would determine cell seeding efficiency, cell diffusion and the mechanical strength of the scaffold.The author discusses the assessment techniques for the braided bio-degradable nerve regeneration conduit, such as weight method, density method and image method. The result suggests that weight method is imprecise and unrecurrent though simple and easy to operate. So image method is introduced to assess the porosity of braided scaffold which is good at both factors.Surface pictures of braided nerve conduit are taken by micro-camera, transformed to a digital image and than analysised by Matlab7.0 with image technique. The testing result shows that image method is feasible to evaluate the porosity of braided nerve conduit and can provide reliable characteristic parameter for correlative research due to strictness of the theory, accuracy of the method and well recurrence of the test result.The author than test the porosity of braided conduits by image method, discuss the relationship between porosity and braiding parameters such as spindle number, tube diameter, yarn density and braiding angle and investigate the effect porosity on its compressive capability and degradative performances in vitro. Moreover, the influence of porosity on cell seeding efficiency is also studied cooperating with the Shanghai First People's Hospital, the result reveals that higher porosity is favorable for the cell growth. Unfortunately, scaffolds with high porosity would possess low mechanical strength, hence there must be a compromise between porosity and mechanical properties of scaffolds.Owing to the unique characteristic of braided nerve tube, there's no special technique for its porosity testing or not so precise as need, not to mention steady and universal standards, which frustrated the further investigation on porosity and the effect on cell growth of braided conduit which need to be solved urgently.Achievements obtained from this research work could be used to test porosity, build a testing and control system and establish a foundation for a further investigation and clinical application of braided nerve conduit.