Study Of Composite Drug-loaded Nerve Conduit With Electrical Stimulation

There are around one million persons suffered from nerve injury.The treatment of peripheral nerve injury is a worldwide medical problem.The majority of nerve repair researchers are committed to develope multifunctional nerve conduit to treat nerve damage because of many problems and limitations in traditional treatment methods in clinic.Although all kinds of nerve conduits were used in clinic gradually.Ideal nerve conduit has not been preparad.Due to the difficulties existing in nerve conduit,TA of conductive polymer were selected to prepare,then PDLLA and NGF were added by physical composition to develop PDLLA/TA/NGF composite drug-loaded nerve conduit with electrical stimulation.First,EM TA was preparad by oxidative coupling polymerization.EM TA was reduce to obtain LE TA.Composition,structure and microstructure of EM TA and LE TA were characterized by fourier transform infrared spectroscopy(FTIR),ultraviolet(UV),mass spectrometry(MS),thin layer mass spectrometry(TLC)and scanning electron microscopy(SEM).Conductivity of EM TA and LE TA wer tested by resistivity meter.Finally,the effect of reation ratio,reaction time,concentration of protonic acid on the yield of TA was dicussed via orthogonal experiment,the reaction ratio of 1:1,the reaction time of 2 h and the HCl concentration of 2 mol/L were the optimum conditions for synthesis of TA.PDLLA/TA composite nerve conduits with different amounts of TA were prepared with physical recombination.The effects of doping of TA on the mechanical properties,hydrophilicity,electrical conductivity and microstructure of the composite nerve conduits were tested.The results showed that the PDLLA/TA composite nerve conduit has good mechanical and hydrophilic properties,and the conductivity meets reuirement of electrical stimulation for nerve growth.At the same time,the mechanical properties,hydrophilicity,and conductivity increase with the amount of doping of TA.Finally,the best amount of doping of TA is 10% considered its micro morphology.In vitro degradation testing of nerve conduit was carried out to determine medium pH value changes,weight loss rate during the process of degradation and to observe the structure changes after the degradation.Results showed that the doping of TA promoted the speed of degradation of PDLLA/TA.The degradation rate of PDLLA/TA was controlled,and the problem of acidic environment during the degradation of PDLLA conduit was improved.Bovine serum albumin was loaded in PDLLA/TA nerve conduits by physical blend to investigate the effect of doping amount of TA and pH in degradation solution on the release behavior of BSA.PDLLA/TA/NGF nerve conduit were prepared by loading NGF refer to BSA as model drug.The the NGF release behavior was investigated.The result showed that the PDLLA/TA/NGF drug-loaded nerve conduit achieved slow release in different acid and alkali environments.The RSC96 and PC12 nerve cells were co-cultured with different nerve conduits.The method of CCK-8 was selected to evaluate the cytotoxicity of the conduit The ability of dhesion and proliferation of cells on the surface of nerve conduits were observed by immunofluorescence and SEM.The results showed that the doping of TA and NGF promoted cell proliferation and adhesion,and the PDLLA/TA/NGF nerve conduit has good cell affinity.The effect of voltage,electricity,and electrical stimulation time on cells were investigated.The results showed that outer electrical stimulation promoted the proliferation and growth of both cells.The voltage of 250 mV,the current of 150 mA and the time of 36 h were the optimal parameters for electrical stimulation.SD rats were used as animal model of sciatic nerve defect.The growth of sciatic nerve and the functional recovery of muscles were analyzed.after one and three months.Repair ability of different nerve conduits on sciatic nerve demage were assessed.Gait and histological analysis showed that the PDLLA/TA/NGF composite nerve conduit was best for nerve repair and was similar to the autograft group.In summary,PDLLA/TA/NGF composite drug-loaded nerve conduit had good biocompatibility and electrical stimulation and could promote nerve regeneration.It would be expected to be used in the treatment of peripheral nerve injury.