New Strategy For Electrochemical Analysis Of Live Mouse Brains

Electrochemical analysis of live mouse brains is of great importance and full of challenge.As the highest central nervous system,the brain contains various types of neurotransmitters,reactive oxygen species,amino acids,ions,enzymes and other substances.Abnormalities of above substances can cause damage to neurons and brain tissues,and may further lead to many diseases,such as Alzheimer’s disease,Parkinson’s disease and depression.Until now,the detailed mechanism of many diseases is unclear for the lack of suitable and powerful tools for in-situ and real-time monitoring of related substances.Electrochemical in-situ analysis with high sensitivity,high time and spatial resolution,is widely used in the real time detection of target substances in the live mouse brains.Therefore,electrochemical analysis of live brain through microelectrodes has been became a main method for understanding life systems,physiology and pathogenesis at the molecular level.However,the abundant biological thiols and various similar molecules in the complex brain can cause false signal and unreliability.In addition,neurons are extreme susceptible to electrical signals applied by electrochemical device,which can affect neuronal firing rates.In view of above challenges,this topic developed the following strategies.Firstly,designing and synthesizing electrochemical probes for the recognition of target substance.The obtained probes were modified onto electrode in order to improve the selectivity.Secondly,considering the thiol ligands on Au surface can be replaced by abundant biological thiols,electrochemical biosensor based on Au-C≡C self-assembled surface was developed to improve the stability.Thirdly,in light of the interference on spontaneous neuronal activity by electrochemical biosensor,photoelectrochemical biosensor is developed for the determination of biomolecules,which without applied potential can avoid the effect on neuronal activity.Based on above strategies,the following works were performed.（1）An electrochemical biosensor based on Au-C≡C self-assembled surface was developed.Compared with the biosensor constructed by Au-S-C bond,this biosensor showed significant electrochemical performance and high stability,including low formal potential,improved current,fast electron transfer rate and anti-biothiols interference.Furthermore,DNA-MB was optimized as a reference element for providing abuilt-in correct.As a result,a ratiometric electrochemical biosensor with high selectivity was developed for the detection of Fe²⁺.The sensor with high accuracy and high selectivity showed a good linearity for determination of Fe²⁺from0.2 to 120μM.Finally,the biosensor was used for biosensing of Fe²⁺in the live brain and the results demonstrated that Fe²⁺had an increase in the hippocampus,cortex and striatum in the live brains of AD model compared with that in normal mouse.Using this powerful tool together with fluorescent probes,Fe²⁺in the cortex and striatum were mediated by c AMP to get into neurons.The results provided a theoretical basis for the pathogenesis of AD.（2）A novel electrochemical probe was designed and synthesized for the specific recognition of MAO-A according to the MAO-A inhibitor.By co-modifying the MAO-A probe and inner refererent probe（DNA-MB）onto electrode through Au-C≡C self-assembled surface,a ratiometric and turn-on electrochemical sensor with high selectivity was developed for the accurate quantification of MAO-A.The biosensor showed high accuracy demonstrated a good linearity with the activity of MAO-A from 0.6 to 40 m U m L^-1with a low detection limit of 120μU m L^-1.Finally,the developed sensor was applied for evaluating the MAO-A activity in the brains of normal mouse and live AD mouse.Using this strategy,it was found that MAO-A activity was increased by 127±7%and 178±10%in the cortex and thalamus of AD mouse models compared to those obtained in the normal mice.Moreover,it revealed that MAO-A increased the influx of Ca²⁺into neurons via transient receptor potential melastatin channels（TPRM2）in AD mouse brains.This study provided new insights for understanding AD diseases.（3）A photoelectrochemical sensor was developed and applied to the detection of biological species.The developed sensor without applied voltage avoided the interference on spontaneous neuronal activity and could be used for simultaneously monitoring of biological species and recording of electrophysiological signal.Firstly,gold nanorods（Au NRs）with absorbance of 785 nm were prepared and modified on the surface of anatase Ti O2 electrode.Under 785 nm light irradiation,Au NRs exhibited strong LSPR and induced charge separation at the surface.The photoelectrons were transferred to the conduction band of Ti O2,and the photogenerated holes were neutralized by electrons from ONOO^-probe on the surface of Au NRs.This behavior prevents the recombination of photoelectrons and photogenerated holes generated from Au NRs,thus forming a current.As a result,a photoelectrochemical microsensor is developed for selectivily monitoring of ONOO^-.The determination of ONOO^-can be achieved by the photocurrent.The developed photoelectrochemical microsensor showed a good linearity for determination of ONOO^-from 10 n M to 60μM.Finally,the microsensor with high accuracy,high stability,high selectivity and high reproducibility was successfully used for the detection of ONOO^-in the cortex of mcie with hypertension model.The results demonstrated that cortical ONOO^-in the mice of hypertension model increased by89.6%compared with that in normal mice.In this work,a near-infrared light-mediated photoelectrochemical microsensor was used for the detection of biomolecules in live brain for the first time,which provide new a strategy for simultaneously monitoring of biological species and recording of electrophysiological signal...