Study On Novel Analytical Methods And Their Applications For The Detection Of Monoamines

As major neurotransmitters, catecholamines (including dopamine, epinephrine, norepinephrine and serotonin) play important roles in the function of brain and nerve signal transduction, They are directly involved in a variety of biological activities, such as analgesics, physical movement, mental activity, sleep, awakening, stress, etc. The levels of catecholamines in the body are closely related to human health, pathology studies show that they are associated with cerebrovascular disease, traumatic brain injury; excess of monoamine neurotransmitters can produce large amounts of reactive oxygen species causing neuronal apoptosis. Therefore, it is necessary to develop acurate, sensitive, rapid and portable methods to facilitate the detection, quantification of catecholamines.Recently, with its prominent feature, modified electrode has been widely concerned. People endow the electrode with new and specific feature through molecular design, assembly on the electrode surface, modified electrode can greatly improve the detection sensitivity and selectivity, therefore, they are widely applied in the analysis. For example, modified electrode is widely used in the direct electrochemical detection of target analytes; modified electrode also can be employed in capillary electrophoresis and high performance liquid chromatography system for the simultaneous measurements of analytes with similar molecular structure. Particularly, capillary electrophoresis-amperometric detection coupled with modified electrode has been developed as an effective analytical method due to its high separation speed, sensitivity and efficiency, low sample consumption and short analysis time, it has been applied in fields of drug analysis, food analysis, life science research, etc.Catecholamines as research object in this paper, we focus on the study of the novel strategy for the rapid determination of catecholamines. In this dissertation, we constructed a chemically modified electrode and establish a rapid, sensitive, accurate, technology for selective detection of dopamine; capillary electrophoresis amperometric detection coupled with modified electrode for simultaneous detection of four catecholamines, more important, the effect of noise exposure on catecholamines in hippocampus and hypothalamus was investigated for the first time; capillary electrophoresis-amperometric detection coupled with Field-amplified sample stacking for the analysis of four analytes in biological sample with high levels of salt.Chapter1OverviewIn chapter1, we mainly introduced the conception and classification of neurotransmitter, the development of determination methods for low levels of catecholamines, and then reviewed the basic principle, application and development of modified electrode, meanwhile, the principle, application of capillary electrophoresis-amperometric detection coupled with modified electrode was highlighted.Chapter2Highly Sensitive and Selective Determination of Dopamine in the presence of Ascorbic Acid at Titanium Silicate-1FilmIn this paper, TS-1/Au-Pt/Nafion modified electrode was constructed for selective detection of dopamine for the first time, the TS-1/Au-Pt film was characterized with scanning electron microscope (SEM) and its electrocatalytical behavior was studied by electrochemical methods. It showed that the TS-1/Au-Pt modified electrode had excellent electrocatalytical effect to dopamine, the electrocatalytical responses increased linearly with DA in the range of0.5μM～0.02mM, with the detection limit of0.16μM (S/N=3). Meanwhile, under the experiment condition, dopamine could go through Nafion membrane while ascorbic acid couldn’t, therefore, TS-1/Au-Pt/Nafion modified electrode could selective detection of dopamine in the presence of ascorbic acid.Chapter3Simultaneous determination of monoamines in rat brain with Pt/MWCNTs@Pdop hybrid nanocomposite using capillary electrophoresis- amperometric detectionIn this article, polydopamine (Pdop) functionalized multi-walled carbon nanotubes (MWCNTs@Pdop) was firstly synthesized and employed as the template for the dispersion of Pt nanoparticles (NPs) to form Pt/MWCNTs@Pdop hybrid nanocomposite. The characterizations of the Pt/MWCNTs@Pdop were investigated by SEM, TEM, XRD and voltammetry. Based upon the Pt/MWCNTs@Pdop nanocomposite, a modified carbon disk electrode was fabricated and successfully applied for the simultaneous detection of four important monoamines (MAs), including dopamine (DA), epinephrine (E), norepinephrine (NE) and serotonin (5-HT) using capillary electrophoresis-amperometric detection (CE-AD) system. Compared with the bare electrode, the four analytes at the Pt/MWCNTs@Pdop electrode exhibited higher sensitivity, broad linear responses from1.0to1.0×102nmol/L. The detection limits (S/N=3) were lower than8.1×10-10mol/L. More importantly, the effect of noise exposure on MAs in hippocampus and hypothalamus was investigated for the first time. Compared with the control group, the levels of the MAs all varied to different extents after rats receiving the same noise stimulation. The results showed that the proposed method could be applied in determination of low levels of MAs in biological samples and screening the target molecules for the diagnosis and treatment of various related diseases.Chapter4Field-amplified sample stacking combined with capillary electrophoresis-Pt/MWCNT@Pdop modified electrode amperometric detection method for determination of four catecholamines in urine and dialysateThe analysis of monoamine neurotransmitters in vivo is of great significance for clinical medicine, life science research. Due to the high levels of salt in biological sample, the detection sensivity is seriously affected. In this chapter, we used field amplification sample stacking method coupled with chemically modified electrode to improve the detection sensitivity of capillary electrophoresis, we optimized the separation and detection conditions by selecting the appropriate organic reagent, the concentration of organic reagents, injection time and injection pressure. Pt/MWCNT@Pdop modified electrode as working electrode, the capillary electrophoresis-amperometric detection coupled with field amplification sample stacking was successfully employed for determination of catecholamines in urine and dialysate.