Design And Synthesis Of Probe Molecules For H₂O₂ Recognition And Its Application In Situ Analysis Of Rat Brain

Hydrogen peroxide（H₂O₂）is the material basis of brain nerve activity,which is indispensable for maintaining normal brain function and plays an important indicator role in the study of brain neurophysiological process and pathological mechanism.Abnormal H₂O₂level will cause oxidative stress,which leads to serious damage of protein and DNA and is linked to neurodegenerative diseases such as Parkinson’s and Alzheimer’s disease.In this paper,based on the summary of the research status of H₂O₂detection at home and abroad,a reasonable H₂O₂recognition molecule was designed and modified on the microelectrode,and a ratio electrochemical microsensor with high sensitivity and high selectivity was constructed,which was successfully applied to the in vivo detection of H₂O₂level in rat brain.Based on the basic principle that borate pinanol ester can be used as the reaction site of H₂O₂for electrophilic reaction,H₂O₂-mediated oxidation reaction of aryl borate pinanol ester will generate corresponding phenols and generate corresponding electrochemical signal on the electrode.Seven arylborate pinanol esters were designed to detect H₂O₂.Gold nanoparticles were deposited on the microelectrode,and arylborate pinanol esters were modified on the microelectrode by Au-S bonding adsorption.Cyclic voltammetry was used to prove that the reaction product of the compounds with H₂O₂was an adsorption process and redox reaction occurred on the electrode.The results of differential pulse voltammetry tests and theoretical calculation show that o-Cl-DBP was superior to other compounds in terms of current density,electron transfer rate,surface coverage ratio,reaction time,oxidation peak potential and Gibbs free energy.Finally,o-Cl-DBP molecule was selected as the best molecule for the detection of H₂O₂,which laid a foundation for the further design of ratio-based electrochemical microsensors with high sensitivity and high selectivity to realize the sensitive detection of H₂O₂in vivo.The selected o-Cl-DBP molecule was selected as the recognition element of H₂O₂and modified on the electrode through Au-S bond cooperation.The oxidation peak current density of o-Cl-DHP generated by reaction of o-Cl-DBP and H₂O₂was changed with the difference of H₂O₂concentration.The defect oxidation peak of graphene was introduced to act as an internal reference unit to provide built-in correction while increasing the conductivity of the electrode and improving the sensitivity and accuracy of the sensor.According to the linear relationship between the ratio of the oxidation peak current density of o-Cl-DHP and the defect oxidation peak current density of graphene and H₂O₂concentration,a CFME/Ox GO/Au/o-Cl-DBP ratio electrochemical microsensor was constructed for the accurate determination of H₂O₂.The sensor had good selectivity,stability,reproducibility,biocompatibility and good anti-interference ability.It was not affected by p H,and had good linearity in the range of H₂O₂concentration 0.5-600μM.Utilization of ratio electrochemical microsensor on the normal mice and PD mice in mouse cerebral cortex,striatum and hippocampus in different areas of the three H₂O₂levels in vivo detection,successfully detected the normal mice and PD rat cerebral cortex,striatum and hippocampus average concentration of H₂O₂,found that H₂O₂concentration of PD rats compared with normal rat would rise.In addition,H₂O₂and Cat were injected into the cerebral cortex of rats,and reproducibility of different electrodes was measured,which proved that the sensor had good stability in the in vivo measurement process,providing a reliable detection platform and a new means for the diagnosis of PD disease.