Electrochemical Detection Of Several Vascular Endothelial Injury Markers And Bioactive Small Molecules

The basic principle of electrochemical biosensors and the application of metal nanoparticles as well as conducting polymer in electrochemical biosensing are introduced in this thesis.Some conducting composites that were doped with gold nanoparticles,boronic acid derivatives and molecules containing amino groups were prepared on glassy carbon electrode,respectively,by using the one-step protocol based on the polymerization of the electroactive dye,azure A.The qualitative detection of ascorbic acid?vitamin C,Vc?,glucose and von willebrand factor?vWF?are realized,respectively.The main works are listed as follows.1.The modified glassy carbon electrode?GCE?with poly?azure A?-gold nanoparticles composite?PAA-Au NPs?was prepared by using AA and HAuCl₄ based on cyclic voltammetry.The electrochemical response of Vc on the different electrodes were investigated,respectively.The electrochemical detection of Vc was performed by using the composite-modified GCE under optimum experimental conditions.The peak current in cyclic voltammogram displayed a linear relationship with the Vc concentration from 0.02-2 mM with a detection limit of 6?M.A simple method with low cost and good selectivity for the detection of Vc was developed and it was employed to measure the Vc content in fruit juice.2.Poly?azure A?-gold nanoparticles-4-mercaptophenylboronic acid composite?PAA-Au NPs-MPBA?on GCE was prepared by using AA,MPBA and HAuCl₄ based on cyclic voltammetry.The electropolymerization of the dye,the generation of Au NPs and the immobilization of the boronic acid derivative were simultaneously achieved in the potential cycling process.The structure and component of the modification film was verified by scanning electron microscopy?SEM?and X-ray photoelectron spectroscopy?XPS?measurements.MPBA on the composites could capture glucose based on the specific boronic acid–diol binding and form a stable 5-membered cyclic boronate ester,which prevented the penetration and the charge transfer of the ferri-/ferrocyanide couple on the electrode surface.The peak-current change in cyclic voltammogram was found to be proportional to the logarithm of the glucose concentration in the range 10 nM-10?M with a detection limit of 4 nM.The proposed sensor exhibited high sensitivity,satisfying stability and good immunity from interference of several physiological compounds and it was successfully applied in the determination of glucose in human serum samples.3.The modified GCE with poly?azure A?-chitosan-gold nanoparticles-cysteine composite?GCE/PAA-CS-Au NPs-Cys?was prepared by using AA,chitosan,HAuCl₄ and cysteine based on cyclic voltammetry and it was characterized with SEM and XPS.The vWF antibodies were immobilized on the electrode surface by using glutaraldehyde as a crosslinking agent.The effect of the immunoreaction on the electrochemical response of the dye polymer on the antibody/composite-modified electrode was investigated.Under optimum experimental conditions,the DPV peak current change was found to be proportional to the logarithm of the vWF concentration from 0.001 to 100?g mL^-11 with a detection limit of 0.4 ng mL^-1.The proposed label-free immunosensor exhibited high sensitivity,wide detection range and good selectivity.The release of vWF by oxidation-injured human umbilical vein endothelial cells?HUVEC-C?,which were induced by H₂O₂,was also investigated based on the proposed electrochemical method.