A New Method For The Determination Of Two Monoamine Neurotransmitters Based On Functionalized Carbon Micro/nano Electrodes

Neurotransmitters are important biochemical molecules that control the behavior and physiological functions in central and peripheral nervous systems.It is the basis for understanding the pathogenesis of neurological diseases and the action mechanism of drugs in vivo to establish the analysis methods of the content and change of neurotransmitters in biological samples,which is of great scientific significance for the prevention and treatment of neurological diseases.The electrochemical methods received much attention in the detection of neurotransmitters in biological samples due to their simplicity,rapid,sensitive,high space-time resolution and real-time in-situ detection.In view of the challenges of electrochemical detection of neurotransmitters in biological samples,such as spatial resolution,sensitivity,selectivity and electrode fouling,this thesis carried out the research work of "Electrochemical methods for the detection of two monoamine neurotransmitters based on functionalized carbon micro/nanoelectrodes".5-hydroxytryptamine(5-HT)and dopamine(DA),two monoamine neurotransmitters,were used as target substances,and carbon fiber microelectrode and carbon nanopipette electrode were used as the base electrode.By functionalized base electrode using gold nano materials for signal amplification and overoxidizing poly pyrrole with anion repulsion propoties,three electrochemical biosensors for monoamine neurotransmitters were constructed for the detection of 5-HT and DA.This thesis consists of 4 chapters.Chapter 1 is introduction,including the classification and function of neurotransmitters,the research progress of electrochemical detection of neurotransmitters,the preparation and classification of carbon microelectrodes,as well as the purpose and contents of this research.Chapter 2 is "highly selective electrochemical method for the detection of serotonin at carbon fiber microelectrode modified with gold nano flowers and overoxidized polypyrrole".A highly selective and sensitive electrochemical method was developed for the detection of 5-HT at gold nano flowers(AuNFs)and overoxidized polypyrrole(OPPy)modified carbon fiber microelectrode(CFME).Carbon fiber was firstly modified with gold nanoflowers using electroless deposition method,and then modified with overoxidized polypyrrole using electrochemical polymerization and overoxidization to obtain OPPy/AuNFs/CFME.The obtained OPPy/AuNFs/CFME was characterized by field emission scanning electron microscopy and electrochemical techniques.It was found that the OPPy/AuNFs/CFME showed good sensitivity for the detection of 5-HT in the range of 0.01-7.0 ?mol/L with detection limit of 2.3 nmol/L,and negligible interferences from ascorbic acid,5-hydroxyindole acetic acid and uric acid.The OPPy/AuNFs/CFME was successfully applied to the detection of 5-HT in human serum samples with good recovery.The work demonstrates that the electrochemical method,incorporating signal amplification of AuNFs with higher anion repulsion of OPPy,provides a promising tool for the detection of 5-HT in biological systems.Chapter 3 is "electrochemical methods for the detection of dopamine released from cells at carbon nanopipette electrode modified with gold nanoparticles or overoxidized polypyrrole".A sensitive electrochemical method was developed for the detection of DA released from PC 12 cells at gold nanoparticles modified carbon nanopipette electrode(AuNPs/CNPE)and overoxidized polypyrrole modified carbon nanopipette electrode(OPPy/CNPE).Firstly,a carbon nanopipette electrode with a diameter of 300 nm was fabricated by depositing pyrolytic carbon on a pulled quartz nanopipette using chemical vapor deposition(CVD)method.Secondly,gold nanoparticles were deposited onto the carbon nanopipette electrode using electroless deposition method to form the gold nanoparticles modified carbon nanopipette electrode.And overoxidized polypyrrole was deposited onto the carbon nanopipette electrode using electrochemical deposition method to form the overoxidized polypyrrole modified carbon nanopipette electrode.The obtained AuNPs/CNPE and OPPy/CNPE were characterized by field emission scanning electron microscopy and electrochemical techniques.It was found that the AuNPs/CNPE showed good sensitivity for the detection of DA in the range of 0.08-8 ?mol/L with a detection limit of 6 nmol/L,and OPPy/CNPE showed good sensitivity for the detection of DA in the range of 0.01-34 ?mol/L with a detection limit of 2 nmol/L.DA released from PC 12 cells was monitored electrochemically with the AuNPs/CNPE and OPPy/CNPE placed adjacent to the cell by differential pulsed voltammetry(DPV)and amperometric i-t curve,respectively.The work demonstrates that the electrochemical method,incorporating signal amplification of gold nanoparticles with high spatial resolution of nanoelectrode,and combined with higher anion repulsion of OPPy and high spatial resolution of nanoelectrode,provides promising tools for the detection of electroactive biological molecules in biological systems.In the later stage,we will modify the gold nanoparticles and overoxidized polypyrrole on the carbon nanopipette electrode to further improve the anti-fouling performance of the electrode.Chapter 4 is conclusion and prospect.The main conclusions and shortcomings are summarized and analyzed of this paper in this chapter.And the work that needs to be further improved and supplemented is prospected.