Fabricating Conductive Films With Micropatterns For Enhancing The Nerve Regeneration

Nerve injury is a disease with high rates of morbidity and disability,which not only impairs the sensory and motor function,but also may lead to multiple organ dysfunction.Presently,the treatment of peripheral nerve injury is still a worldwild medical problem.Due to many problems and limitations of traditional clinical treatments,lots of researchers are dovoted to developing multifunctional nerve conduit for the treatment of nerve injury.And the hollow nerve conduits displayed an outstanding prospect in clinical theraphy.However,its poor permeability and lack of direction lead to poor recovery effect of nerve function.Recently,it has been shown that the nerve conduit with oriented microstructure can effectively improve the regeneration ability and functional recovery of neurons in the injured site.Hence,the multifunctional film with oriented micropatterns and electroconductivity was constructed by directional freezing.The physical guidance of oriented micropatterns combined with drug induction could effectively promote the growth of neurons and axon regeneration.And the growth behavior of neurons depended on the sulfation pattern of chondroitin sulfate(CS).Preliminary in vivo experiments showed that the scaffold had a good repair effect on sciatic nerve injury in rats.The main research contents of this paper are as follows:(1)Cellulose nanocrystal(CNC)was grafted with hyperbranched polyglycerol,which was further polymerized to form a conductive shell layer of polypyrrole by an oxidant catalyzed method to obtain conductive nanoparticles CCHP.The composite conductive film PCC was prepared by vacuum filtration of CCHP and collagen(Col)solutions.By adjusting the weight ratio of CCHP to Col,we screened out the optimal film with good conductivity,strong mechanical strength(tensile strength >20 MPa,strain capacity >220%),oriented microstrcture,high swelling ratio(>500%),and excellent thermal stability.(2)The biocompatibility and activity of PCC conductive membranes were investigated in vitro and in vivo.The results of MTT and live-death staining showed that the rate of living cell was in the range of 95%-120%.The immunofluorescence results showed that the hippocampal neurons cultured on the PCC films grew well and displayed good regeneration of axons.Especially,the neurons grew in parrallel with the oriented micropatterns.By constructing the model of sciatic nerve injury,PCC nerve conduits showed better nerve regeneration compared with the autologous transplantation.(3)The directional freezing strategy was explored to construct directional micropatterns on the surface of the PCC film,which was coded as PCCF.The width with 10-350 ?m of the oriented micropattern on the film was controlled by adjusting the speed of directional freezing and composition ratio of the PCC film.CS played an important role in neurodevelopment and pathology,and showed pleiotropic effects on neuron growth.Different subtypes of CS were coated on the micropatterns of the PCCF film.We investigated the inducted effects of orientated micropatterns and drugs on neurons.The results showed that axons grew in a narrow angle range of 0-30° under the guidance of micropatterns and drugs.Induction by CS with different sulfation patterns,neurons displayed a growth rate in the range of 10%-150%,and the axon length ranged from 0 to 200%.Finally,CS lyase(Chon ABC)could reduce the pleotropic effect of CS on the axon orientation,axon length and cell survivals.