Direct Electrochemistry And Biosensing Applications Of Glucose Oxidase And Hemoglobin

Protein is a kind of biological macromolecules with special catalysis, the directelectrochemistry research of protein has important position in the process of life. It is essentialfor investigating structure-function relationship of proteins, thermodynamics and kinetics ofprotein electron transfer. In our work, we mainly chose glucose oxidase and hemoglobin asthe research object. The protein or enzymes was immobilized on the electrode surface to studythe direct electrochemistry of proteins and enzymes, and in order to build the electrochemicalbiosensor. The performance parameters of the constructed biosensor were obtained, such aslinear range and detection limit etc. In addition, the stability and repeatability of eachbiosensor was also studied.A new glucose biosensor was constructed by immobilizing glucose oxidase in thechitosan-multi-walled carbon nanotube/gold nanorods composite membrane. TheChit-MWCNTs/GOD/AuNRs/gold electrode (GE) displayed a pair of well-defined andreversible redox peaks with the formal potentials (Eθ’) of-0.384V in0.1mol/L pH7.0PBS.The apparent heterogeneous electron transfer rate constants of GOD confined toChit-MWCNTs/AuNRs membrane was evaluated as11.03s1according to Laviron’s equation.The surface concentration (Γ*) of the electroactive GOD in the film was estimated to be(7.03±0.02)×10-11mol·cm2. The electrocatalytic oxidation to glucose ofChit-MWCNTs/GOD/AuNRs/GE was also studied. Its apparent Michaelis-Menten constantfor glucose was1.34mmol/L. The experiment results showed that the linear dependence of theelectrocatalytic current of the biosensor was from2.80×10-4to5.88×10-3mol/L, the detectionlimit of the sensor was2.06×10-5mol/L(S/N=3). Moreover, the biosensor showed rapidresponse to glucose, good stability and reproducibility.A hydrogen peroxide biosensor was constructed by immobilizing hemoglobin in theChit-SWCNTs/AuNRs composite membrane in order to study its direct electron transfer andelectrical catalytic performance. The composite membrane displayed a pair of well-definedand reversible redox peaks with the formal potentials of-0.313V in0.1mol/L pH7.0PBS.The surface concentration of Hb in the film was estimated to be (1.36±0.2)×10-9mol·cm-2. The apparent heterogeneous electron transfer rate constants of Hb confined toChit-SWCNTs/AuNRs membrane was evaluated as1.95s1according to Laviron’s equation.The obtained apparent Michaelis constant was2.47×10-5mol/L by electro-catalytic reductionto hydrogen peroxide, which suggests that the composite film has a good affinity forhydrogen peroxide. Moreover, the sensor showed rapid response to hydrogen peroxide, goodstability and reproducibility.A hyper-branched platinum nanoparticles was synthesized through reduction topotassium chloroplatinite by using ascorbic acid as a reducing agent. The synthesizednanomaterial HPtNPs was characterized by transmission electron microscopy and fieldemission scanning electron microscope. This nanomaterial was then used in the constructed ofChit-MWCNTs/PtNPs composite membrane and achieved the direct electron transfer ofhemoglobin in the composite film. The electrocatalytic to hydrogen peroxide ofChit-MWCNTs/PtNPs/GCE was also studied and has good electrical catalytic reduction tohydrogen peroxide. The experiment results showed that the linear dependence of theelectrocatalytic current of the biosensor was from6.67×10-5to1.53×10-4mol/L, the detectionlimit of the sensor was9.43×10-6mol/L(S/N=3). Its apparent Michaelis-Menten constant forhydrogen peroxide was1.35×10-5mol/L. It could be developed for hydrogen peroxidebiosensor.