Direct Electrochemistry And Electrocatalysis Of Redox Proteins Immobilized On Carbon Ionic Liquid Electrode

Electrochemical behaviors of the redox proteins can not only provide organisms in the process of energy conversion and metabolic information, but also can achieve the direct electron transfer between redox proteins and electrodes without mediator, which has great significance for the construction of the third generation biosensors. The direct electron transfer rate of redox protein with the bare electrode is slow. The reasons can be summarized as follow:most proteins have larger molecular weight and their electrical activity group or redox center was far from the electrode surface and usually deeply buried within the protein molecules; the orientation of the protein on the electrode surface is negative. Ionic liquids have high electrical conductivity, wide electrochemical window and good stability, which is widely used in electrical analysis. Nanometer materials have exhibited large specific surface area, unique electrical and catalytic properties, good biocompatibility and easy functionalization, which make them widely used in electrochemical biosensors. Ionic liquids and nanomaterials provides opportunities to build appropriate biosensors. In this paper different nanomaterials are used as modifiers to fabricate several kinds of proteins modified electrodes with the direct electrochemistry and electrocatalysis of proteins investigated in details.1. Titanium dioxide (TiO2) nanowires was synthesized and used for the realization of direct electrochemistry of hemoglobin (Hb). By using carbon ionic liquid electrode (CILE) as the substrate electrode, TiO2-Hb composite was casted on the surface of CILE with chitosan as the film forming material. UV-Vis and FT-IR spectra confirmed that Hb retained its native structure in the composite. Direct electron transfer of Hb on the modified electrode was investigated by cyclic voltammetry with a pair of quasi-reversible redox waves appeared. Electrochemical behaviors of Hb on the modified electrode were carefully investigated. The Hb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid and NaNO2 with wider linear range and lower detection limit.2. Nickel oxide (NiO) nanoflowers was synthesized and used for the realization of direct electrochemistry of horseradish peroxidase (HRP). By using carbon ionic liquid electrode (CILE) as the substrate electrode, NiO-HRP composite was casted on the surface of CILE with chitosan as the film forming material. UV-Vis and FT-IR spectra confirmed that HRP retained its native structure in the composite. Direct electron transfer of HRP on the modified electrode was investigated by cyclic voltammetry with a pair of quasi-reversible redox waves appeared. Electrochemical behaviors of HRP on the modified electrode were carefully investigated. The HRP modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid3. Three-dimensional graphene (3DGR) was directly formed on the surface of carbon ionic liquid electrode (CILE) by electrodeposition. By using 3DGR/CILE as the substrate electrode, a new electrochemical biosensor was prepared by immobilization of hemoglobin (Hb) on the electrode surface with a thin film of chitosan (CTS). Electrochemical investigation indicated that a pair of well-defined redox peaks appeared on cyclic voltammogram, indicating the realization of direct electron transfer of Hb with the underlying electrode. The modified electrode displayed good electrocatalytic activity to the reduction of trichloroacetic acid (TCA), and the catalytic reduction peak current had a good linear relationship to TCA concentration in the range from 0.4 to 26.0 mmol/L with the detection limit of 0.133 mmol/L (3σ).4. A three-dimensional graphene (3DGR)-nickel oxide nanostructure was synthesized by electrodeposition method and used for the electrode modification with a 1-hexylpyridinium hexafluorophosphate (HPPF6) based carbon ionic liquid electrode (CILE) as the substrate electrode. Electrochemical investigation indicated that a pair of well-defined redox peaks appeared on cyclic voltammogram, indicating the realization of direct electron transfer of Mb with the underlying electrode. The Mb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid (TCA) in the concentration range from 0.5 to 32.0 mmol/L with the detection limit of 0.16 mmol/L (3σ).