Electrical Signals Mediated By Nanomaterials Induce Stem Cells To Differentiate Into Nerve Cells

With the development of economy,the popularization of transportation tools and the increase of traffic accidents,the cases of nerve injury are also increasing.For thousands of years,the repair of nerve injury has been a difficult problem that cannot be solved by the medical community,and this problem has become one of the urgent problems to be solved by today's scientific community.The reason of nerve injury can't heal by itself like skin injury and bone injury is that neural stem cells only exist in the brain after adults and cannot renew themselves,so nerve injury cannot rely on stem cells to repair itself.Bone marrow mesenchymal stem cells(BMSCs)are widely present in bone tissue at all ages.However,BMSCs belong to mesodermal cells,and it is difficult to differentiate into nerve cells of ectodermal.In order to solve this problem,tissue engineering combines engineering with life science,and uses materials to create conditions for the construction or repair of tissues or organs in vivo and in vitro.In recent years,people have paid more and more attention to this problem.Tissue engineering consists of seed cells,scaffold materials and growth factors that regulate differentiation.But how to use scaffold materials and signals to control the direction of stem cell differentiation has always been the focus of research.The direction and speed of stem cell differentiation can be influenced by the surface structure and properties of materials,cell-to-cell interactions,and external physical and chemical signals.Previous studies have targeted intervention on stem cell differentiation through the selection of appropriate nanomaterials and physical signals.Physical signals have many advantages that chemical signals do not have,such as good stability,long duration,controllable duration,etc.Electrical signals,in particular,have been widely used in pain relief,wound healing and neuromuscular retraining due to their advantages of safety,economic convenience and so on.In addition,the good biocompatibility of nanomaterials chemical microenvironment good stability,small side effects on other cells,and a rich selection of morphology and structure,which provide more strategies to regulate stem cell fate,so using nanomaterials as scaffold materials to build cell culture in vitro microenvironment gradually become a consensus.Several researchers have used nanomaterials to induce the directed differentiation of stem cells.In these experiments,nanomaterials combined with electrical stimulation proved to be an effective means of inducing bone marrow mesenchymal stem cells to differentiate into neurons.However,the transmission of electrical signals often requires the use of wires,so the previous experiments used external wires when the electrical signals were applied,which limited the promotion in clinical practice.Using the physical properties of nanomaterials,such as piezoelectric or electromagnetic induction,to transform the external field energy into radio signals,thus stimulating the neural differentiation of stem cells,is the breakthrough point to solve this problem.Hydrogel is a kind of hydrophilic good three-dimensional polymer network structure,can rapidly swelling after soaking and keep a large amount of water stable for a long time,because of good piezoelectric responsive,biocompatibility,biological activity,flexibility,this material has been widely applied in biological field,in the treatment of skin lesions,3 d train,biological sensing,Breakthroughs have been made in antimicrobial materials,but there is still little research on stem cells.The combination of excellent piezoelectric property and cell crushing instrument of hydrogel can perfectly solve this problem.Therefore,more and more people believe that piezoelectric nanomaterials and bone marrow mesenchymal stem cells are the ideal choice for the treatment of nerve injury in tissue engineering to repair spinal cord injury.Carbon is an element widely found in nature.Coal,graphite,diamonds and other substances commonly found in People's Daily life are all composed of carbon.Carbon atoms are hybridized and connected to each other by covalent bonds to form graphene.There are many kinds of graphene depending on the way carbon atoms are connected.Recently,there have been many reports about magic Angle graphene.Graphene has good electrical conductivity and adsorption,as well as good biocompatibility and antimicrobial properties.Due to its excellent characteristics,it has been favored by researchers in various fields,and has been used in biomedicine,biosensor,precise drug delivery and other aspects.However,the current research and application in biology is mostly 2D graphene,while the research on 3D graphene is still relatively few.3D graphene has many advantages in inducing stem cell differentiation.For example,the filament of 3D graphene can well induce the growth of axons of neuronal cells and provide support for them.Three-dimensional graphene can also better mimic the internal microenvironment.In previous studies of three-dimensional graphene,nanogenerators or fixed power sources were used to transmit electrical signals to three-dimensional graphene.All these devices required the use of external wires,which greatly limited the application of experimental results.How to use the characteristics of scaffold material itself to generate radio signals is the breakthrough to solve this problem.Based on the above ideas,this paper aims to use the structure and physical properties of nanomaterials to generate radio signals to induce the directional differentiation of stem cells to nerve cells.The specific work of this paper includes the following two parts:1.In this paper,the piezoelectric hydrogel was taken as the research object,and the regulation of stem cell differentiation was studied through the piezoelectric property and surface structure of the hydrogel.The results showed that:(1)Hydrogels are a kind of hydrophilic fiber reticular structure gels with irregular reticular structure with fiber width ranging from 5nm-50 nm.(2)hydrogel have good biocompatibility,when training to fifth days,cell number is 30% 50%,the size of the glass cell and shows good proliferation trend,living death dyeing showed that on day three cells in the hydrogel maintained good biological activity,cell attached with electron microscope photos also show up 2 days in cell can be well attached on the hydrogel.(3)the cell disruptor and water gel combined piezoelectric,using ultrasound to stimulate water gel,although by cellular pseudopod fiber of hydrogel catch attached,also can have certain piezoelectric effect,but in the process of cell differentiation tends to limit stimulus tend to achieve better effect,so we use ultrasound to stimulate water gel to make its produce more current.The hydrogels have good piezoelectric properties through the tests of piezoelectric response microscope(PFM)and oscilloscope.(4)The Quantitative real time polymerase chain reaction(q-PCR)results confirmed the effect of the surface structure and physical properties of the fibrous hydrogel on the differentiation of stem cells.The surface structure and piezoelectric properties of hydrogels can promote the differentiation of rat BMSCs into neurons,and the neural stem cell marker Nestin,neuronal marker microtubule-associated proteins 2,and neuronal marker microtubule-associated proteins 2,respectively,can be used to promote the neural differentiation of rat BMSCs.Map2),type III tubulin(?-tubulin III,Tuj1),and glial cell-specific marker glial fibrillary acidic protein(GFAP)m RNA expression were significantly increased.After 1 day of inoculation,the expression levels of Nestin and GFAP genes increased by 8 and 450 times,respectively.With the prolongation of treatment time,the gene expression of early neuronal marker Tuj1 and late neuronal marker Map2 were also up-regulated to 140-fold and 56-fold.The results of skeleton staining also confirmed that the hydrogel itself could promote the differentiation of rat bone marrow mesenchymal stem cells into nerve cells.(5)Under the condition of ultrasound,cells were stimulated more by electric current,and differentiation became faster and deeper.After 15 days of ultrasound treatment,functional neurons were produced.Immunofluorescence staining and PCR results showed that Map2,a marker of mature neurons,and ?-tubulin?(Tuj1),a marker of early neuronal development,were significantly increased compared with the non-ultrasonic-treated group.Therefore,it is a reliable method to stimulate BMSCs to differentiate into neuronal cells by using the combination of the cell fragmentation apparatus and the available hydrogels under the premise of induction without adding additional growth factors.In addition,the piezoelectric water gel the physical properties of the material itself is also conducive to the differentiation of bone marrow stem cells into nerve cells,the cellular pseudopod catch attached to the role of water gel fibers can make filaments produce deformation,electrical charge form electrical stimulation signal and by direct contact with the function of material and stem cell to cell.It can promote the expression of neural genes and induce the differentiation of bone marrow mesenchymal stem cells into neurons.This experiment confirmed the effect of piezoelectric property of hydrogel on stem cell differentiation,and obtained fully functional neuron cells through ultrasonic stimulation,which is of great significance for nerve injury repair.2.R-GO three-dimensional graphene scaffold was used to accelerate the differentiation rate of neural stem cellsBased on the electromagnetic induction phenomenon,this paper used R-GO three-dimensional graphene scaffold and magnetic field rotating electrogeneration device to accelerate the speed of neural stem cell differentiation through the structure and electrical signals of the scaffold.Research shows that:(1)The combination of rotating magnetic field and static 3D graphene scaffold can simulate graphene cutting magnetically sensitive lines and trigger the generation of induced current.The addition of Poly 3,4-ethylenedioxythiophene(PEDOT)can greatly improve the conductivity of 3D graphene scaffold.(2)The current generated by a three-dimensional graphene scaffold under a rotating magnetic field can accelerate the differentiation of neural stem cells.Adding PEDOT to the three-dimensional graphene scaffold with improved electrical conductivity significantly accelerated the differentiation rate of neural stem cells.Compared with the 3D graphene scaffolds without PEDOT,the expression of neuronal cell-related proteins Tuj1 and Map2 were significantly increased.The proportion of neurons is significantly higher than that of glia.In this chapter,based on the principle of electromagnetic induction and the conductor properties and three-dimensional structure of 3D graphene,a rotating magnetic field is used to drive it to generate induced current.This current accelerated the neural differentiation of NSCs on 3D graphene and increased the proportion of neuron differentiation.The system only uses the physical and structural properties of 3D graphene to transform the external magnetic field into an internal wireless current without adding any neuro-inducing factors,so as to accelerate nerve differentiation.This study will provide ideas for clinical use of magnetic field to introduce radio stimulation,and provide theoretical and data support for nerve repair.This paper aimed to the problems facing the nerve injury repair,using tissue engineering technology,using the combination of nanometer materials and the physical signal induced mesoderm between bone marrow mesenchymal stem cells to the ectoderm neuronal cell differentiation,or to speed up the neuronal differentiation of neural stem cells and ratio,for the repair of nerve injury provides a new thought and method.