The Study Of Electrochemical Biosensor Based On MnO₂ Nanosheet

A very important factor in biosensor research is the immobilization of biomolecules. Immobilization of biomolecules onto electrode surfaces is important in the understanding of protein properties and also in the development of novel biosensors.Modified electrodes based on nanomaterials combined with high surface area and good electrochemistry abilities can largely improved electrical responses and the detection sensitivity. We applied the novel MnO₂ nanosheet to the immobilization of heme proteins and investigated the electrochemical properties. The main contents of the thesis are given as follows:1. A novel nanomaterial - MnO₂ nanosheet was firstly applied to the immobilization of myoglobin (Mb) as a support matrix. Fourier transform infrared (FTIR) and Circular dichroism (CD) spectra showed that Mb almost retained secondary structure in the film. In MnO₂ nanosheet film, Mb realized its direct electron transfer and gave a pair of nearly reversible cyclic voltammetric peaks, whereas no redox pair was observed for Mb/the precursor layered manganese oxide film. Moreover, the immobilized Mb displayed the feature of a peroxidase and acted in an electrocatalytic manner in the reduction of hydrogen peroxide, nitrite and oxygen. The detection of sulfides was performed via the inhibiting action on the Mb/MnO₂ nanosheet/glassy carbon electrode (GCE). After 14 days, Mb/MnO₂ nanosheet/GCE retained 91% of its initial response to electrocatalytic reduction of hydrogen peroxide.2. MnO₂ nanosheet was also applied to the immobilization of cytochrome c (Cyt c) as a support matrix. FTIR spectra showed that Cyt c almost retained secondary structure in the film. In MnO₂ nanosheet film, the electrocatalytic manner in the reduction of hydrogen peroxide of Cyt c was retained. In additional, (Cyt c/MnO₂ nanosheet)_n layer-by-layer was fabricated on the surface of GCE. Electrochemical impedance spectroscopy was used to monitor the growth of the film. The amount of Cyt c and MnO₂ nanosheet in the bilayer increased linearly with the number of the bilayer.