Electrochemical Biosensors Of Redox Proteins Based On Ionic Liquids And Nanomatierial Interface

Proteins are important biological macromolecules in the life sciences. Study on thedirect electrochemical behaviors of redox proteins and enzymes on the electrode are ofgreat importance both for studying the intrinsic heme behaviors of proteins andfabricating new kinds of biosensors without the addition of mediators. Ionic liquid (IL) isliquid electrolyte, which consists of a small anion and a bulky organic cation such asimidazolium and pyridinium. IL also possesses the properties such as high ionicconductivity and electrochemical stability, which makes it a prospective candidate for theelectrochemical applications. It not only can be used as solvent and supporting electrolyte,but also the binders and modifiers to prepare the modified electrode. In this thesis, IL andnano-materials are used as modifiers to fabricate three kinds of heme proteins modifiedelectrodes and the direct electrochemical behaviors of heme proteins are studied in details.The thesis can be summarized as follows:1. A novel biocomposite biomaterial was fabricaed by mixing Co3O4 nanoparticles,nanoparticles and myoglobin (Mb) together, which was further immobilized on thesurface of a carbon ionic liquid electrode (CILE) with N-hexylpyridiniumhexafluorophosphate as the binder. Ultraviolet-Visible (UV-Vis) and Fourier transforminfrared (FT-IR) spectroscopic results showed that Mb in the composite film remained itsnative structure. A pair of well-defined redox peaks appeared on cyclic voltammetric,indicating that the direct electron transfer of Mb with the underlying electrode wasrealized, which can be attributed to the favored orientation of Mb in the compositematerials with the synergistic effect of nanoparticles Co3O4 and nanoparticles Au and theelectron transfer rate was promoted. The composite material modified electrode showed excellent electrocatalytic ability towards the reduction of different substrates such astrichloroacetic acid (TCA) and NaNO2 with good stability and reproducibility, indicatingthe potential applications of Co3O4-Au nanoparticle to the electrochemical biosensors.2. A novel biocompatible sensing strategy based on graphene (GR), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) and chitosan (CTS) composite film forthe immobilization the myoglobin (Mb) was adopted. UV-Vis and FT-IR spectroscopicresults showed that Mb in the composite film remained its native structure. Directelectron transfer and bioelectrocatalytic activity of Mb in the nanocomposite film werefurther investigated. Cyclic voltammetric recults indicated that a pair of reversible redoxwaves of myoglobin appeared, indicating the direct electrochemistry of Mb was realized.The result can be attributed to the different properties of the material used, including largesurface-to-volume ratio and high conductivity of GR, high ionic conductivity of IL, theinteraction of IL with RG, and good biocompatibility of CTS, which enhanced theenzyme absorption and promotes direct electron transfer between redox enzymes and thesubstrate of electrodes. The CTS-GR-IL-Mb/CILE showed good electrochemical catalgticability to the reduction of the trichloroacetic acid (TCA), which exhibit the potentioalapplication in the third-generation biosensor.3. CILE was constructed based on the substitute of paraffin with N-butyl pyridiniumhexafluorophosphate (BPPF6) to mix with graphite powder. The mixture of Nafion, IL,GR and Nano-CaCO₃ were immobilized on the surface of CILE to fabricate the modifiedelectrodes denoted as Nafion/Hb-CaCO₃-GR-IL/CILE. The characteristics of Hb in themodified films were investigated by UV-Vis spectrum and FT-IR spectrum,Spectroscopic results indicated that Hb molecules retained its native structure in thecomposite film. A pair of well-defined and quasi-reversible cyclic voltammetric peaksappeared and the electrochemical parameters were calculated. The Nafion/Hb-CaCO₃-GR-IL/CILE showed good electrochemical catalgtic ability to the reduction of thetrichloroacetic acid (TCA).