Electrochemical Detection Of Dopamine And Its Interaction With Biological Macromolecules

Dopamine detection is of significant importance in physiological research, clinical application and food safety. Chemically modified electrodes have several advantages in that the preparation procedure is simple, the detection is fast with high sensitivity, which aroses the research workers'attentions. In this thesis, a series of studies on the new materials for developing novel modified electrodes and their application. In addition, the binding of dopamine to BSA is also presented. The main points of this thesis are summarized as follows:1. Based on the conductivity of polypyrrole (PPy) and carbon nanotubes (CNTs), tiron-doped PPy and CNTs fabricated on low resistance monolayer-modified glassy carbon electrode. The layer-by-layer modified electrode was sensitive to dopamine. Parameters in?uencing the dopamine response were optimized. High performance of the sensor was obtained such as a wide concentration range from 2.0×10-8 M to 1×10-4 M, low detection limit (3 nM), low background current, high stability and reproducibility. Because of the anion dopant, it showed excellent capacity of resisting ddisturbance.2. With the crosslinking agent of PPy, CNTs-DNA hybrids and tiron modified electrode was fabricated by one step codeposition. It could be used to selectively detect dopamine under physiological pH conditions. The electrode showed such characteristics as biological catalytic activity of DNA, the good conductivity of CNTs and PPy, therefore the sensitivity greatly improved. It presented high stability and reproducibility with a low detection limit (5×10-10 M).3. DNA-functionalized graphene modified electrode was fabricated by cyclic voltammetric reduction of a colloidal solution of graphene oxide and controlled dc potential deposition of DNA. The modified electrode exhibited biological catalytic activity of DNA and excellent conductivity of graphene. The sensor displayed high sensitivity, a wide dynamic range, a detection limit of 3 nM, good reproducibility and long-term stability.4. The binding of dopamine with bovine serum albumin (BSA) was investigated by fluorescence and Fourier-transform infrared (FTIR) spectroscopy. The association constants, thermodynamic parameters, quenching rate constants at three different temperatures and the number of binding sites were also determined. It is a static quenching procedure. Synchronous fluorescence spectroscopy illustrated that dopamie interacted with both tyrosine residues (Tyr) and tryptophan residues (Trp) of BSA. The thermodynamic study and IR spectra confirmed that hydrophobic and hydrogen bonds interactions were both the predominant intermolecular forces during the binding procedure. The structure of the BSA changed when it binded with dopamine.