Polymeric Nerve Conduits with Contact Guidance Cues Used in Nerve Repair

In the modern life,the nerve injury frequently happens due to mechanical,chemical or thermal accidents.In the trivial injuries,the peripheral nerves can regenerate on their own;however,in most of the cases the clinical treatments are required,where relatively large nerve injury gaps are formed.Currently,the nerve repair can be accomplished by direct suture when the injury gap is not too large;while the autologous nerve graft working as the gold standard of peripheral nerve injury treatment for nerve injuries with larger gaps.However,the direct suture is limited by heavy tension at the suture sites,and the autologous nerve graft also has the drawbacks of donor site morbidity and insufficient donor tissue.Recently,artificial nerve conduits have been developed as an alternative for clinical nerve repair to overcome the limitations associated with the above treatments.In order to further improve the efficiency of nerve conduits,various guidance cues are incorporated,including physical cues,biochemical signals,as well as support cells.First,this paper reviewed the contact guidance cues applied in nerve conduits,such as lumen fillers,multi-channels and micro-patterns on the inner surface.Then,the paper focused on the polymeric nerve conduits with micro inner grooves.The polymeric nerve conduits were fabricated using the phase inversion-based fiber spinning techniques.The smart spinneret with grooved die was designed in the spinning platform,while different spinning conditions,including flow rates,air-gap distances,and polymer concentrations,were adjusted to investigate the influence of fabrication conditions on the geometry of nerve conduits.The inner groove size in the nerve conduits can be precisely controlled in our hollow fiber spinning process,which can work as the efficient contact guidance cue for nerve regeneration.

Eutectic-reaction brazing of Al_(0.3)CoCrFeNi high-entropy alloys using Ni/Nb/Ni interlayers

In this study,a novel eutectic-reaction brazing of Al_(0.3)CoCrFeNi high-entropy alloys(HEAs)^(1)was investigated with a design of laminated Ni/Nb/Ni interlayers.The typical Al_(0.3)CoCrFeNi brazing seam consisted of proeutecticγ,the lamellar eutectic structure composed of face-centered cubic(FCC)phase(eutecticγ)and C14 Laves,as well as a few amounts of Nb based solid solution.A high density of nanoscale ordered L1_(2)(γ)phase was precipitated withinγphase matrix.With the brazing temperature raised from 1200 to 1320℃,the dissolution volume of Al_(0.3)CoCrFeNi alloy into Ni-Nb liquid was increased.The microstructure of the brazing seam changed from hypereutectic(blocky Laves+γphase)to eutectic(Laves+eutecticγ)to hypoeutectic structures(proeutecticγ+Laves/γeutectic structure).The shear strength of joints was increased gradually due to the formation of eutectic lamellae and the cellular growth of proeutecticγphase.The maximum shear strength of the joint brazed at 1320℃for 10 min was up to 592 MPa,reaching 95%of the base metal.The joint mainly ruptured in the soft proeutecticγphase in a ductile fracture mode.