The In-situ Synthesis Of Fe-N-C Nanozyme On Carbon Fiber And The Related Application In Vivo Electrochemical Analysis

Brain neurochemicals play significant roles in neural system,widely involving in processes such as spreading neural signals between brain neurons,maintaining the function of neural system,and promoting the growth and repairment of brain neurons.The abnormal levels of brain neurochemicals caused by genetic or environmental changes may contribute to some brain diseases,such as Parkinson’s disease,Alzheimer’s disease,and so on.Therefore,the development of a biocompatible brain sensing platform to realize real-time detection of brain neurochemicals with high selectivity in living animals is of great significance for determining the specific molecular basis of different pathological processes,prevention,diagnosis and treatment of brain diseases.The electrochemical sensing platform based on carbon fiber microelectrode has high spatiotemporal resolution and is an important means for the analysis of neurochemicals in vivo.Studies have demonstrated that modulation of electron transfer kinetics on the electrode interface and ion transport behavior can effectively improve the sensitivity and selectivity of detection of neurochemicals in vivo.Nanozymes,the nanomaterials with enzyme-like properties,can be used to catalyze electrochemical redox reactions of physiologically relevant neurochemicals.Taking this into consideration,we make full use of Fe-N-C nanozymes to constract the robust carbon fiber microelectrode/brain interface with excellent catalytic properties for detection of important brain neurochemicals in vitro and vivo.The details are as follows:(1)The in-situ synthesis of Fe-N-C nanozymes on carbon fiber and study on their electrocatalytic performance.Through a series of reactions including diazotization reaction,m-diphenylamine polymerization,Fe3+ anchoring,and high temperature pyrolysis,the in-situ synthesis of Fe-N-C nanozymes on carbon fiber(Fe-N-C/CF)were obtained and characterized by scanning electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy,and so on.And then,the electrochemical behavior of brain neurochemicals(such as hydrogen peroxide(H2O2),dopamine(DA),5-hydroxytryptamine(5-HT)),and bisphenol A(BPA),an organic compound that affects endocrine disorders,were preliminarily studied on the Fe-N-C/CF microelectrode.The results showed that Fe-N-C nanozymes had a good catalytic effect on the reduction of H2O2 and the oxidation of DA,5-HT,and BPA,and the Fe-N-C/CF microelectrode is expected to be used for in vivo electrochemical detection.(2)Electrochemical study of in vivo monitoring of H2O2 with Fe-N-C nanozymes/carbon fiber microelectrode.On the basis of the above study,the electrochemical behavior of H2O2 on Fe-N-C/CF microelectrode was deeply studied.The results showed that the peroxidase-like activity of Fe-N-C nanozymes can effectively accelerate the kinetic rate of H2O2 redox reaction on the electrode surface,reduce the overpotential,eliminate the interference of O2,and effectively improved the sensitivity,selectivity,time resolution,and stability of the electrochemical detection of H2O2.Moreover,the prepared Fe-N-C/CF microelectrode had a rapid response ability to in situ microperfusion of H2O2 in vivo,which preliminarily proved its feasibility in the detection of H2O2 in vivo.(3)Electrochemical study of in vivo monitoring of DA with Fe-N-C nanozymes/carbon fiber microelectrode.On the basis of the above study,the electrochemical behavior of DA on Fe-N-C/CF microelectrode was deeply studied by utilizing the oxidase-like activity of Fe-N-C nanozymes.The results showed that the surface-modified Fe-N-C nanozymes can modulate the electron transfer kinetics and ion transport behavior on the microelectrode surface,thereby accelerating the oxidation of DA,reducing the anodic overpotential,and can effectively inhibit the electropolymerization of dopamine and its oxidation products,showing good performance.Thus,the sensitivity,selectivity,temporal resolution,and stability of the prepared Fe-N-C/CF microelectrodes were effectively improved.Moreover,the prepared Fe-N-C/CF microelectrode had a rapid and obvious response to DA generated by high K+stimulation in vivo,which confirms its ability to detect DA in vivo and provides a new method for the detection of DA in vivo.