Investigation Of Redox Protein Modified Electrodes Based On Ionic Liquids And Nanomaterials

Due to their unique physical and chemical properties, ionic liquids and nanomaterials have been attracted more and more attention in the fabrication of redox proteins modified electrodes. In this dissertation, ten kinds of redox proteins modified electrodes were fabricated based on ionic liquids and nanomaterials and the behaviors of direct electrochemistry and electrocatalysis for hemoglobin (Hb), myoglobin (Mb) and glucose oxidase(GOx) modified on these electrodes were investigated in details. These research are not only significant to enrich research content of the direct electrochemsitry of redox proteins and their interrelated biosensors, but also can broaden the application range of ionic liquids and nanomaterials. The dissertation consists of four chapters. The author's main contributions are summarized and presented as follows:1. By casting method, four kinds of protein modified electrodes, including Hb-HA-BMIMBF4-GCE, Hb-CS-BMIMPF6-Si02/GCE, Hb-CS-BMIMBF4-clay/GCE and Mb-CS-BMIMBF4-GR/GCE, were fabricated and their behaviors of direct electrochemistry and electrocatalysis were investigated, respectively. The spectral results revealed that Hb and Mb could retain their native tridimensional structure in these composite films. The electrochemical results indicated that direct electron transfer were all occurred between these two proteins and the underlying electrodes, and their electrchemical response were enhanced obviously, which should be attributed to the presence of ionic liquids. Furthermore, Hb and Mb entrapped in these electrodes exhibited excellent electrocatalytic activities toward the reduction of H2O2 with wide linear ranges. Thus, these composite films could provide novel platform for the study of the electrochemical behavoirs of redox proteins.2. Electrodeposition and layer-by-layer assemble methods were employed to prepare modified films. Then, three kinds of protein modified electrodes, including GOx-IL-GNP-IL-SWCNT/GCE, Hb/IL/DNA/PDDA/ITO electrode and Mb/DNA/CILE, were fabricated and their electrochemical behaviors were carefully investigated. The corresponding electrochemical methods were presented for determination of glucose, H2O2 and trichloroacetic acid (TCA), respectively. The experimental results indicated that a pair of of well-defined, quasi-reversible cyclic voltammetric peaks appeared for GOx, Hb and Mb on these modified electrodes, repectively. GOx assembled on GOx-IL-GNP-IL-SWCNT/GCE showed excellent electrocatalytic activity toward the oxidation of glucose. The linear range for the determination of glucose was found to be 2.0×10-6 to 5.0×10-5 mol-L-1 and the detection limit was 8.0×10-7 mol-L-1 (S/N=3). The apparent Michaelis-Menten constant (KM) was further calculated as 2.21×10-5 mol-L-1. Hb modified on Hb/IL/DNA/PDDA/ITO electrode exhibited excellent electrocatalytic activity toward the reduction of H2O2. The reduction peak current had a linear relationship with the concentration of H2O2 in the range from 1.0×10-6 to 3.8×10-4mol-L-1 and the detection limit was 1.O×10-7 mol·L-1 (S/N=3). Mb immobilized on Mb/DNA/CILE showed excellent electrocatalytic activities toward the reduction of H2O2 and TCA with the linear range of 1.0×10-6～1.6×10-4mol·L-1 and 5.0x10-4～4.0×10-2 mol-L-1. The detection limits were 2.0x10-7 mol·L-1 and 8.3x 10-5 mol·L-1 (S/N=3), respectively. Thus, these three kinds of composite films showed potential application for other redox proteins to achieve their direct electron transfer.3. Ionic liquid modified carbon paste electrode (CPE-IL) was constructed with the BPPF6 and paraffin as binder. Then CPE-IL was employed as the basal electrode, Hb/CoNP/MWCNT/CPE-IL, HA/CeO2/Mb/CPE-IL and GG/MgO/Hb/CPE-IL were further fabricated by electrodeposition and step-by-step methods. The electrochemical characteristics of Hb and Mb modified on these electrodes were investigated in detail and the corresponding cyclic voltammetry was employed to determine H2O2 and TCA. The results suggested that the addition of a little paraffin could deduce the background current generated mainly by ionic liquid. While, BPPF6, CoNP/MWCNT, HA/CeO2 and GG/MgO composite film acted very important roles in enhancing the direct electron transfer between these two proteins and electrodes, respectively. Furthermore, these two proteins immobilized on the electrodes also showed excellent electrocatalytic activities toward the reduction of H2O2 and TCA. For Hb modified on Hb/CoNP/MWCNT/CPE-IL, the surface concentration of electroactive Hb was calculated to be 8.92×10-10mol-cm-2. The values of KM for H2O2 and TCA were 2.61 x10-5 mol·L-1 and 2.31×10-4mol·L-1, respectively. For Hb immobilized on GG/MgO/Hb/CPE-IL, H2O2 could be detected in a wide linear range of 2.0×10-7～1.7×10-4 mol·L-1 and a very low detection limit of 5.0×10-8 mol-L-1. Therefore, the redox proteins modified electrodes with the CPE-IL as platform render a great potential in fabricating the third-generation biosensor.