Application Of Nanocomposite Modified Electrode For Direct Electrochemistry And Electrocatalysis Of Heme Protein

It is well-known that the direct electrochemistry of redox proteins and enzymescan establish a desirable model for studying the redox mechanism of proteins inbiological systems, and understanding the relationship between their structures andbiological functions. Therefore, direct electron transfer between native redox-activeproteins and electrodes have attracted considerable attentions in the past several decades.However, due to the deep burying of electroactive center in the protein structure, thedenaturation of proteins on the bare electrode surface or the unfavorable orientation onthe electrode interface, it is difficult for proteins to realize the direct electron transferprocess on the bare electrode. So protein film electrodes with various kinds of modifiersor promoters have been devised to accelerate the electron transfer rate. Among themnanomaterials with different morphologies have been used due to their specific properties.In this paper we fabricated four different kinds of nanocomposite modified electrodes,these can be summarized as follows:1. Nitrogen-doped graphene (NG) was synthesized and used for the investigationon direct electrochemistry of hemoglobin (Hb) with a carbon ionic liquid electrode as thesubstrate electrode. Due to specific characteristics of NG such as excellentelectrocatalytic property and large surface area, direct electron transfer of Hb was realizedwith enhanced electrochemical responses appeared. Electrochemical behaviors of Hb onthe modified electrode were carefully investigated with the electrochemical parameterscalculated. The Hb modified electrode exhibited excellent electrocatalytic reductionactivity toward different substrates, such as trichloroacetic acid and H2O2, with widerdynamic range and lower detection limit. These findings show that NG can be used forthe preparation of chemically modified electrodes with improved performance and has thepotential applications in electrochemical sensing.2. A carbon ionic liquid electrode (CILE) was fabricated by using ionic liquid1-hexylpyridinium hexafluorophosphate (HPPF6) as modifier and hierarchical LiFePO4 nanostructures have been synthesized via a facile hydrothermal technique and applied tothe protein electrochemistry for the first time. UV-vis and Fourier transform infraredspectra were employed to characterize Hb retained its native structure in the resultingHb-LiFePO4membrane, A pair of well-defined reversible redox waves of hemoglobinwas appeared with Epa=-0.285V and Epc=-0.363V (vs.SCE) in phosphate buffersolution (0.1mol L-1) at the scan rate of100mV/s. The result can be attributed to thespecific characteristic of LiFePO4nanoparticle and the advantages of CILE, whichfacilitated the electron transfer rate. and hemoglobin could exhibit its bioelectrocatalyticactivity toward TCA and H2O2, Under the optimal conditions the catalytic current was inlinear to TCA concentration in the range from0.2to65.0mmol L1with the detectionlimit calculated as6.8×10-5mol/L (3σ). The fabricated biosensor displayed the advantagessuch as high sensitivity, good reproducibility and long-term stability.3. The direct electrochemistry and electrocatalysis of myoglobin (Mb) immobilizedon a SnO2@GR composite film modified carbon ionic liquid electrode was investigated.The nanocomposite was characterized by scanning electron microscopy, UV-vis andFourier transform infrared spectra and electrochemistry. A pair of well-defined redoxpeaks appeared on cyclic voltammogram, indicating that direct electron transfer of Mbwith the underlying electrode was realized, which could be attributed to the presence ofSnO2@GR composite that can enhanced the electron transfer between the protein and theelectrode. The nanocomposite modified electrode exhibit good stability and catalyticactivities for the electrocatalytic reduction of and NaNO2with wider dynamic range andlow detection limit.4. Graphene (GR) nanosheets and ZnO nanoparticle were electrodeposited on thesurface of CILE with a potentiostatic method step by step. The fabricated ZnO/GR/CILEwas used as a new platform for the protein electrochemistry, and Myoglobin (Mb) wasimmobilized on its surface with nafion as the film forming material. Electrochemicalbehaviors of Mb were carefully investigated with the electrochemical parameterscalculated. The Nafion/Mb/ZnO/GR/CILE showed good electrocatalytic ability to thereduction of trichloroacetic acid (TCA) with the detection limit (3σ) as8.67mmol/L.