Construction Of Carbon Fiber Microelectrode-based Biosensor And Its Application In Biological Sample Analysis

Carbon fiber microelectrode(CFME)has high spatial-temporal resolution and high detection sensitivity due to its small electrode size.It can be used for nondestructive quantitative analysis of various components in vivo.In order to improve the anti-pollution performance,detection sensitivity and selectivity of CFME,four methods of modified CFME were introduced in this paper.The modified CFME was applied to biological samples,and the mechanism of modification was further explored.The details are as follows:In Chapter 1,the development and application of microelectrode detection system since it was established more than two centuries ago are described.Furthermore,the application of microelectrode,carbon fiber microelectrode,electrode modification method,electrode modification material and electrochemical analysis method are described in detail.In Chapter 2,An initial potential of 1.5 V was applied to the CFME using the current-time curves method,and the peak current of neurotransmitters in the electrochemically treated CFME was increased dramatically.Our study furthered understanding of the activation mechanism of CFMEs treated electrochemically in pure water.The regenerated CFME was quite stable and had a good reproducibility.It is expected to be applied to activate and regenerate electrodes contaminated in the complex biological microenvironment monitoring.In Chapter 3,A one-step potentiostatic deposition method was used to deposit graphene oxide quantum dots(GQDs)on the surface of carbon fiber microelectrode,and then a layer of Nafion film was coated on the surface of modified electrode to obtain the Nafion / GQDs / CFME.The Nafion / GQDs / CFME was applied to the detection of dopamine,adrenaline(E),noradrenaline.In a certain concentration range,the oxidation peak current of DA,E,NE showed a good linear relationship with its concentration.The modified electrode has good reproducibility,good electrode stability and simple preparation method.It can be applied to the determination of catecholamine neurotransmitters in real blood samples.In Chapter 4,the existing synthesis method of spherical nano gold is improved to realize the synthesis of spherical nano gold with controllable particle size under simple conditions.Different sizes of spherical nano gold particles are deposited on the surface of carbon fiber microelectrode by one-step potentiostatic deposition method to obtain the carbon fiber microelectrode modified by nano gold(GN/ CFME).The electrochemical behaviors of dopamine(DA),norepinephrine(NE),ascorbic acid(AA),and potassium ferricyanide were studied before and after electrode surface modification.The results show that the modified electrode can repel the negative material by electrostatic repulsion and catalyze the electrochemical response of the positive material to realize the selective determination,and can be applied to the actual biological sample detection.In Chapter 5,an electrochemical method for real-time dynamic detection of aloe polysaccharide in water storage tissue gel layer of aloe leaves was established.The aloe polysaccharides in aloe plants under different growth conditions were monitored in-situ by high-sensitivity carbon fiber microelectrodes modified with gold nanoparticles(AuNPs/CFME),to evaluate the real-time changes of aloe polysaccharides in the environment under stress.The experimental results show that the AuNPs/CFME has significant electrocatalytic activity to aloe polysaccharides in aloe water storage tissue.The dynamic changes of aloe polysaccharide in aloe plants under different growth environments have significant statistical differences.The modified electrode was successfully applied to the dynamic change of aloe polysaccharide in aloe plants for real-time monitoring,which made the electrochemical detection method a promising method for monitoring the photosynthesis intensity of plants.