The Preparation Of Hydrogen Peroxide Electrochemical Biosensor Based On Carbon Nanotubes

Biosensor is a technology of penetrating mutually biological, chemical, materials, medicine, physics and other subjects. Electrochemical biosensors are widely used for the assay of food industrial, environmental and clinical analyses because of the advantages of this approach including their simple-design, inexpensive instrumentation, rapid analysis, high-sensitivity, low-cost and sensitivity. However, in the construction of electrochemical biosensors, the method of immobilizing biological molecules effectively determines the stability, sensitivity and selectivity of biosensors. In this thesis, the electrochemical biosensors based on different immobilization methods and different transducers have been developed for protein determination by electrochemical and spectral detection.Part 1 Preparated the hydrogen peroxide biosensor based on sol-gel, multi-walled carbon nanotube and horseradish peroxidase.A hydrogen peroxide biosensor was constructed by immobilizing of horseradish peroxidase with sol-gel and multi-walled carbon nanotubes. Firstly, multi-walled carbon nanotubes added to sol-gel solution, secondly, the sol-gel with multi-walled carbon nanotube was fixed on the surface of gold electrode by electrodeposition. The horseradish peroxidase was immobilized by adsorption. The immobilization of enzyme was achieved by using of functional sol-gel. Under the optimized conditions, the linear calibration for H₂O₂ was obtained in the range1.0×10^-8 to 2.5×10^-6 M with a detection of 2.3×10^-9This chapter has improved the method of preparing sol-gel used TEOS or TMOS, which greatly reduced the damage to biological molecules because of the reduction of alcohol or methanol. In this article, the deposition time, the amount of the carbon nanotubes and other conditions were optimized, and the properties of this biosensor were studied.Part 2 Preparated the hydrogen peroxide biosensor based on L-Cysteine, single-walled carbon nanotube and horseradish peroxidase. In the chapter, we have developed a hydrogen peroxide biosensor, in which horseradish peroxidase was immobilized onto a functionalized SWNT through noncovalent method and the carboxylic groups of the functionalized SWNT was immobilized onto a amino-terminated L-cysteine self-assembled monolayer (SAM) preformed on the Au electrode for monitoring the hydrogen peroxide of low concentration. Under the optimized conditions, the linear calibration for H2O2 was obtained in the range1.0×10^-15 to 1.0×10^-14 M with a detection of 3.0×10^-16 M at a signal-to-noise ratio of 3, the sensitivity is 5.48×10⁹ A cm^-2 M^-1In this study, we describe the use of a sodium cholate suspension-dialysis method to adsorb the horseradish peroxidase (HRP) onto single-walled carbon nanotubes (SWNTs). We demonstrate that HRP-SWNTs conjugates can be assembled into amperometric biosensors with which L-Cysteine on a gold electrode through the covalent bond of S-Au and was used as a substrate for the immobilization of enzymes. SWNTs were covalently attached from their carboxylic groups using N-(3-dimethylamino)propyl-N-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide (NHS) as a coupling agent onto an amino-terminated L-cysteine self-assembled monolayer (SAM) preformed on the Au electrode. This method may serve as a model to improve the quality of many other analytical biodevices and allow for miniaturization in biosensor development.