Fabrication Of New Amperometric Biosensor

Biosensors based on enzyme-modified electrodes are valuable in clinical diagnosis, bromatology, environmental monitoring and biochemical analysis. This thesis involves the following subjects relating to hydrogen peroxide biosensor.1) A novel application of Iron(Ⅱ)-Tetra(5, 6-dihydro-1, 4-dithijn) porphyrazine (FePz(dtn)₄) on the Hydrogen Peroxide Biosensor. FePz(dtn)₄ was fixed on the glass carbon electrode by electrodeposition method, and then using colloidal Au to adsorb horseradish peroxidase, polyethylene butyral was used to embed modified electrode. Cyclic vohamrnetry was employed to demonstrate the feasibility of electron transfer between peroxidase and electrode. Linear calibration for H₂O₂ was obtained in the range from 3.5×10^-6-7.35×10^-3mol/L, with the correlation coefficient 0.9994, and the limit is 1.0×10^-6 mol/L at a signal-to-noise ratio of 3. The sensor had good sensitivity, selectivity and stability.2) Poly(4-vinyl-N-carboxymethylpyridine) (QPVP) was well applied to solubilize multiwall carbon nanotubes(MWCNTs). A very simple and effective strategy for preparation a novel hydrogen peroxide biosensor based on electro- deposition QPVP-MWCNT composite doped with HRP in the aqueous solution containing MWCNTs, QPVP and HRP was reported in this paper. The QPVP-MWCNT composite and the fabricated process of biosensor were characterized by UV-visible absorption spectroscopy, scanning electron microscopy, and cyclic voltammetry. Experimental conditions influencing the biosensor performance such as pH, potential were optimized. Under optimized conditions, HRP-QPVP-MWCNT/Au electrode exhibited excellent electrocatalytic activity for the reduction of H₂O₂. The linear range is from 5.0×10^-6 to 8.0×10^-3M with a detection limit of 2.1×10^-6 M (S/N=3).3) Poly(4-vinyl-N-carboxymethylpyridine)(QPVP) was well applied to solubilize multiwall carbon nanotubes (MWCNTs), then a very novel and effective strategy for immobilizing MWCNTs on the gold electrode based on electro-deposition reported in this paper. MWCNTs strengthen the ablity of the electrons' circulation and fixed the nano-Au by chemisorption at the same time. Furthermore, horseradish peroxidase (HRP) was absorbed on the electrode surface through the gold nanoparticles. The performance and factors influencing the performance of the biosensor were studied, Under optimized conditions, HRP/nanoAu/HRP/nanoAu/QPVP-MWCNT/Au electrode exhibited electro-catalytic activity for the reduction of H₂O₂. The linear range is from 9.0×10^-7 to 3.8×10^-3 M with a detection limit of 3.1×10^-7M (S/N=3).4) A convenient and effective strategy for fabrication of hydrogen peroxide biosensor based on sodium alginate (SA), and polyvinyl butyral (PVB) as matrices was reported in this paper. The horseradish peroxidase (HRP) and SA were electro-co-deposited onto gold electrode surface, and the HRP-SA/Au electrode was further coated with PVB. The interaction between the HRP and SA was characterized by UV-vis absorption spectroscopy, and the fabricated process of biosensor was characterized by electrochemical impedance spectroscopy (EIS). The electrochemical characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. Experimental conditions influencing biosensor performance, such as pH, and applied potential were investigated. The biosensor showed a linear response to H₂O₂ over a concentration ranges from 7.0×10^-6 to 4.1×10^-3 M with a detection limit of 1.8×10^-6M based on a signal-to-noise ratio of 3 under optimum conditions.