| L-Dopa?LD?,ascorbic acid?AA?and uric acid?UA?are small biological molecules that exist in the human body.They play a vital role in the metabolism and life activities of the human body,and they also affect human health.Therefore,the rapid,sensitive and selective detection of small biological molecules in the clinical diagnosis of the disease and the pharmacological and physiological activity of the study drug are great significance.The detection method relying on electrochemical sensors has become an important method for the detection of small molecules in the field of analytical chemistry due to its advantages of selectivity,ease of operation,low cost,and high sensitivity.However,the oxidation potential of biological small molecules on the common substrate electrode is very close,and its oxidation product will also pollute the electrode,so the ordinary electrode can not effectively detect small molecules.The chemical bio-modification of the electrode surface to transform it into a micro-surface with special functions is a key step to fully play the role of the modified electrode.Carbon nanomaterials are widely used to modify electrode.Carbon nanotubes have been the focus of chemical workers,due to their unique one-dimensional nanostructures,good electron conductivity,large specific surface area,superior mechanical strength,and excellent electrocatalytic activity.The adoption of the electropolymerization method makes the modified electrode more diversified,and at the same time,the polymeric film exhibits advantages of good stability,controllable morphology,and the like.In this study,electrochemical sensors for the detection of small biomolecules were constructed by combining the advantages of carbon nanotubes and polymeric membranes.The main research work is as follows:1.High sensitive electrochemical sensing platform for the detection of L-Dopa based on electropolymerization glutathione disulfide and multi-walled carbon nanotubes modified electrodeThe carboxylated multi-walled carbon nanotubes?MWCNTs?were dispersedly dripped on the glassy carbon electrode?GCE?surface.The carbon nanotubes can bond to the surface of the glassy carbon electrode due to the?-?stacking between the carbon nanotubes and the glassy carbon electrode.Then,glutathione disulfide was polymerized on a multi-walled carbon nanotubes modified glassy carbon electrode?PGSSG/MWCNTs/GCE?by electropolymerization,and the modified electrode was used for the detection of L-Dopa.The surface morphology and electrochemical properties of the modified electrode were studied by scanning electron microscopy?SEM?and cyclic voltammetry?CV?.The concentration of L-Dopa was measured by differential pulse voltammetry?DPV?.The experimental results show that the electropolymerization glutathione disulfide membrane exhibits a porous three-dimensional structure.The excellent electron transporting capability of multi-walled carbon nanotubes and glutathione disulfide polymeric membrane can accelerate the catalytic oxidation of L-Dopa and increase the current response.Combining the advantages of multi-walled carbon nanotubes and glutathione disulfide polymeric membrane film,modified electrodes exhibit good catalytic activity,high selectivity and sensitivity.The linear range of L-Dopa for the modified electrode was:1.0×10-61.2×10-3 mol·L-1,and the detection limit was 3.3×10-7 mol·L-1.This method provides a new idea for the rapid,simple and sensitive detection of biological small molecules.2.Simultaneous detection of uric acid and L-Dopa based on poly cysteine/multi-wall carbon nanotubes modified electrodeIn the experiment,cysteine?cys?was polymerized on the surface of MWCNTs modified electrode by electropolymerization to form poly cysteine/multi-walled carbon nanotubes modified electrode?Pcys/MWCNTs/GCE?.The surface morphology and electrochemical properties of the modified electrode were investigated by SEM and CV.Simultaneous detection of L-Dopa and uric acid was performed by DPV.The experimental results show that the oxidation potential difference of L-Dopa and uric acid on the modified electrode is 0.13V,and the linear range for detection of L-Dopa and uric acid are 5.0×10-61.5×10-4 mol·L-1 and 6.0×10-61.6×10-4 mol·L-1,the detection limits are 1.6×10-6 mol·L-1 and 2.0×10-6 mol·L-1,respectively.In the synergistic effect of MWCNTs and Pcys,the modified electrode can achieve simple,rapid,sensitive and simultaneous detection of L-dopa and uric acid.3.Poly arginine-?-cyclodextrin film modified electrode for simultaneous detection of L-Dopa,uric acid and ascorbic acidCyclic voltammetry was used to electropolymerize arginine?Arg?and?-cyclodextrin?CD?on the surface of glassy carbon electrode to obtain poly arginine-?-cyclodextrin film modified electrode?P?Arg-CD?/GCE?.The surface morphology of the modified electrode was observed by SEM.The electrochemical properties of the modified electrode were measured by CV and electrochemical impedance spectroscopy?EIS?.Under optimized conditions,the modified electrode has been used to detect a mixed solution of L-dopa,uric acid and ascorbic acid by DPV.The experimental results showed that the peak currents of L-Dopa,uric acid and ascorbic acid were not interfered with each other and the currents were linearly related to their concentrations.The linear detection ranges corresponding to L-dopa,uric acid and ascorbic acid were 5.0×10-63.0×10-4 mol·L-1,8.0×10-62.0×10-4 mol·L-1 and 1.0×10-51.2×10-44 mol·L-1.The detection limits were 1.6×10-6mol·L-1,2.7×10-6 mol·L-1 and 3.3×10-6 mol·L-1,respectively.The method realized simultaneous,rapid,simple and highly sensitive detection of L-dopa,uric acid and ascorbic acid,and provided a convenient and inexpensive method for electrochemical detection of small molecules. |
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