| Reactive oxygen species?ROS?are referred to a class of substances formed from oxygen,have oxygen element and highly active chemical propertie,including superoxide anion?O2·-?,hydrogen peroxide?H2O2?,hydroxyl radical?·OH?,nitric oxide?NO?,peroxynitrite anion?ONOO-?and so on.Under normal physiological conditions,the production and the metabolism of ROS are in a state of dynamic balance.However,when the body was stimulated or diseased,this dynamic balance will be broken,causing the increase of ROS rapidly,and the body cannot remove the rapidly increased ROS in time,leading to the generation of oxidative stress,causing damage to the body and inducing a variety of diseases,especially brain-related diseases,such as ischemic brain disease.Therefore,real-time detection of ROS during oxidative stress in vivo is of great significance to elucidate the mechanism of oxidative stress related diseases.Electrochemical methods are widely used for in vivo measurements due to their advantages of miniaturization,in situ,real-time,and dynamic detection.However,due to the high activity,short life-time and low concentration of ROS in vivo,as well as the complex brain environment,it is still a great challenge to establish methods with high selectivity,high sensitivity and high accuracy for in vivo ROS analysis.Based on a large number of literature researches and the previous works of our group,the following electrochemical sensors were designed and constructed to solve the key issues of electrochemical analysis of ROS in rats brain under ischemic conditions.The details are as follows:?a?A ratiometric electrochemical sensor with high sensitivity and selectivity was developed for peroxynitrite detection in ischemic rats.A novel organic molecule,4-?benzoicacid-1,6-hexanedithiolester-2-yl?-7-?diethylamino?-2-?4-?piperazinyl diferroformamide-1-yl?phenyl?chromenylium?HEMF?,was designed and synthesized.HEMF have ONOO--specific recognition group-benzopyran and electrochemical active group-ferrocene.Self-assembly of HEMF on carbon fiber microelectrodes deposited with gold,an electrochemical sensor with high selectivity,high sensitivity and good biological compatibility was constructed.The electrodeposition gold nanoleaves amplifies the signal,which improves the sensitivity.The internal reference molecule methylene blue?HS-DNA-MB?ware co-assembled on the electrode,forming a ratiometric electrochemical sensor to correct the measurement error caused by the difference between in vivo and external environment.The results show that the constructed electrochemical sensor has a good response to ONOO-and with a wide linear range?20.0 nM2.0?M?,and the detection limits is down to 12.1 nM.Other ROS and metal ions,amino acids and bioactive substances have no obvious interference to the sensor.Finally,the developed electrochemical sensor was successfully applied to in vivo analysis of ONOO-in different brain regions of rat brain during ischemia processes.?b?A turn-on ratiometric electrochemical sensor without enzyme for superoxide detection was developed,and applied to the superoxide detection in ischemia rats.Naphthalen-2-yl diphenylphosphinate?ND?,an organic molecule specifically recognized by O2·-was synthesized.After O2·-specifically react with ND,the naphthol and diphenyl phosphate were generated.The generated naphthol was an electroactive molecule.The oxidation of naphthol was used for the quantification of O2·-.Methylene blue?MB?was introduced as the internal reference molecule to construct the ratiometric electrochemical sensing,improving the accuracy of the ratiometric electrochemical sensor.Carbon fiber microelectrode modified with single wall carbon nanotube?CNT?was used as the base of electrode modification.ND and MB were modified on the electrode by?-?interaction to enhance the stability of electrode modification.It was found that the constructed sensor had a good electrochemical response to O2·-and a wide linear range?2.0?M200.0?M?with a detection limit of 0.52?M.Moreover,other ROS and metal ions,amino acids and bioactive substances have no obvious interference to the sensor.Finally,the constructed non-enzyme O2·-electrochemical sensor was successfully applied to in vivo detection of hippocampus in rats under the condition of ischemia. |
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