Direct Electrochemistry Of Protein Based On Ionic Liquid-nanomaterial Composite

Protein is a kind of important biological macromolecules in life activities, whichis existed in life bodies widely. Studies on the electron transfer process betweenprotein and the electrode has an important significance for us to understand the energyconversion and material metabolism of in vivo, explore the physiological mechanismsof life and develop the third generation of biological sensors. Ionic liquids （ILs） aregreen solvents, with unique physicochemical properties such as higher ionicconductivity, wider potential window, non-volatile and non-toxic. ILs is usually usedas supporting electrolyte and adhesive in the electroanalytical chemistry.Nanomaterials have been widely used in electroanalysis and electrocatalysis due totheir large specific surface and high conductivity. Graphene is a two-dimensional（2-D） sheet of carbon atoms in a hexagonal configuration with atoms bonded by sp2bonds. These bonds and this electron configuration are the reasons for the peculiarproperties of graphene, including special electrical performance, thermal conductivityand optical properties. In this thesis, nano-materials, graphene and IL are used asmodifiers to fabricate different kinds of heme proteins modified electrodes and thedirect electrochemistry of heme proteins on the modified electrodes are studied.1. A carbon ionic liquid electrode （CILE） was constructed based on the substituteof paraffin with N-hexylpyridinium hexafluorophosphate. Then the Hb-Fe₃O₄mixturewas casted on the surface of CILE and left it to dry at room temperature to get anelectrode noted as Hb-Fe₃O₄/CILE. Finally,5μL of1.0mg/mL chitosan （CTS）solution was spread onto the surface of the Hb-Fe₃O₄/CILE to get the final modifiedelectrode （CTS/Hb-Fe₃O₄/CILE）. The modified electrode was characterized byultraviolet-visible, fourier transform infrared spectroscopy, scanning electronmicroscope and cyclic voltammetry. Then electrochemical behaviors andelectrocatalytic reaction of Hb in the modified electrode were carefully investigatedwith the electrochemical parameters calculated.2. A new electrochemical biosensor was constructed based on ZnWO₄nanorod-Hb-CTS composite film. CILE was prepared by using1-Buthylpyridiniumhexafluorophosphate （BPPF₆） as the modifier. UV-vis and FT-IR spectra resultsindicated that Hb remained its native conformation in the composite film. Also thefabricated CTS/Hb-ZnWO₄/CILE was characterized by scanning electron microscopy,electrochemical impedance spectroscopy and cyclic voltammetry. A pair of well defined redox peaks was obtained on the modified electrode, indicated that CTS andZnWO₄composite film provided an excellent biocompatible microenvironment forkeeping the native structure of Hb and promoting the direct electron transfer rate ofHb with the basal electrode. The electrochemical parameters such as the electrontransfer coefficient （α） and the apparent heterogeneous electron transfer rate constant（ks） were calculated respectively. The fabricated Hb modified electrode showed goodelectrocatalytic ability to the reduction of trichloroacetic acid （TCA） in theconcentration range from2.0to10.0mmol/L with the detection limit of0.613mmol/L （3σ）.3. By using BPPF₆based CILE as the substrate electrode, myoglobin （Mb）molecule was immobilized with Fe₃O₄@SiO₂nanoparticles on the surface of CILE toget the modified electrode. The fabricated CTS/Mb-Fe₃O₄@SiO₂/CILE wascharacterized by UV-Vis, FTIR, electrochemical impedance spectroscopy, scanningelectron microscopy and cyclic voltammetry. The direct electrochemical behaviors ofMb in the CTS-Fe₃O₄@SiO₂composite film were carefully investigated with theelectrochemical parameters calculated. The modified electrode showed goodelectrocatalytic behaviors to the reduction of trichloroacetic acid in the concentrationrange from0.2to11.0mmol/L with the detection limit of0.18mmol/L （3σ）.4. A novel NiO mesoporous sphere was synthesized through solvothermal route,which was characterized by powder X-ray diffraction and scanning electronmicroscopy, Then the Hb-ILs-GR-NiO composite materials were immobilized on thesurface of CILE wth nafion film to prepare the modified electrode. Scanning electronmicroscopy （SEM） and cyclic voltammetry were applied to characterize themodification process. The direct electron transfer and electrocatalysis of hemoglobin（Hb） modified electrode were investigated by cyclic voltammetry in0.1mol/L pH7.7phosphate buffer solution （PBS）. The results suggested that Hb molecules in themodified electrode showed excellent direct electrochemistry and electrocatalyticactivity to the reduction of trichloroacetic acid.