Laser Additive Manufacturing Of Electroactive Nerve Scaffolds And Their Cellular Response Reasearch

The repair of peripheral nerve defects,which result in the loss of motor,sensory and autonomic functions,has always been a difficult and hot topic of research at home and abroad.Artificial nerve grafts are made from biodegradable materials to form nerve scaffolds,which can be implanted in the body to induce new nerve growth while gradually degrading until they are completely absorbed,breaking the traditional"tearing down the east wall to patch the west wall"treatment model and bringing new hope for nerve defect repair.However,in order to provide the electrical microenvironment that plays an important role in nerve cell growth,an external power supply or device is usually required,which is complex and inefficient to operate and cannot be widely used.Electroactive nerve scaffolds have great potential for the reconstruction of electrical microenvironments and functional repair of defective nerves.The aim of this paper is to construct an electrical microenvironment suitable for nerve growth to improve nerve regeneration by preparing electroactive nerve conduits using selected area laser sintering（SLS）technology.The specific research work of the paper is as follows:1.Based on bioelectric phenomena,a conductive MXene/PLLA nerve scaffold is constructed to reconstruct nerve signaling and improve nerve regeneration using bioelectric signals.The conductive filler MXene is coated on the surface of PLLA particles by ultrasound-assisted solution mixing,so that MXene is enriched in the interface region between adjacent polymer particles to form a continuous MXene conductive network.Due to the unique shear-free and flow-constrained forming properties of SLS,not only is the network structure retained,but the MXene contacts become tighter,which provides a continuous channel for rapid charge transfer.The results show that PLLA nerve conduits containing 10wt.%MXene displayed a continuous conductive network structure while possessing an excellent electrical conductivity of 4.53 S/m,which is within the appropriate conductivity range for nerve growth（1-10 S/m）.The cellular evaluation confirms that the scaffold significantly promoted cell proliferation,differentiation and protrusion growth.2.Based on the previous chapter,an electroactive NH₂-MXene/PLLA scaffold is constructed based on the principle of electromagnetic induction,triggered by a rotating magnetic field,the scaffold can act as a coil to cut magnetic induction lines,converting magnetic energy into electrical energy and thus generating electrical signals to promote nerve regeneration.The results show that the scaffold has an excellent electrical conductivity of 8.44 S/m.Under the excitation of a rotating magnetic field,the scaffold generates a current of 10μA,which is within the appropriate range for nerve cell growth.In vitro cellular assays confirm that the generated current effectively enhanced PC12 cell proliferation,neurite growth and differentiation-related expression of Nestin,MAP2 and Tuj1.In addition,it promotes the differentiation of PC12 cells into mature neurons.3.The application of photoelectric effect in nerve repair is explored and an electroactive PLLA-Ag/Bi₂S₃ nerve scaffold is constructed,which can generate electrical signals under near-infrared light excitation to improve nerve repair.The scaffold is prepared by growing silver nanoparticles（Ag-NPs）in situ on the surface of bismuth sulfide（Bi₂S₃）and then mixed with PLLA powder by SLS.On the one hand,Bi₂S₃ generates photocurrents under near-infrared light excitation,creating wireless electrical stimulation.On the other hand,Ag-NPs will form a local electric field under light excitation to inhibit the rapid electron-hole complexation of Bi₂S₃.In addition,Ag-NPs will act as electron mediators to accelerate electron transfer and further enhance photocurrents.Electrochemical tests and FDTD simulations reveal the local electric field generated by Ag-NP action on Bi₂S₃,and the enhanced electron-hole separation is evidenced by the reduced photoluminescence intensity.EIS measurements indicate that faster electron transfer occurs on Ag/Bi₂S₃.Furthermore,under near-infrared light excitation,the PLLA-Ag/Bi₂S₃ scaffold generate a photocurrent of 1.03μA.The enhanced photocurrent effectively promotes cell differentiation by upregulating Ca²⁺inward flow and expression of the nerve growth-associated protein Syn1.