The Construction And Application Of The Biosensor Based On Novel Carbon Nanotubes Composites

In recent years, it was reported that fast developments for the application of biosensor in the environmental science, food safety and clinical analysis, accompanied with the development of electrochemical chemistry. The carbon nanotubes, as a special nanomaterials, played important role for the fabrication of biosensor. Aiming at the applying of carbon nanotubes composite in the fabrication of sensor, this study reported several kinds of carbon nanotubes composite, which was used successively in the fabrication of several biosensor including enzyme-modified electrodes and immunsensor.First, this study investigated the fabrication process of carbon nanotubes-methylene blue nanocomposite and its application in the construction of reagentless enzyme-modified electrode. The carbon nanotubes-methylene blue nanocomposite in the solution phase has been characterized by the UV-vis spectrometry, and result suggested the methylene blue can be stably absorbed the surface of carbon nanotubes. The modified electrode based on this nanocomposite gave a couple of well-defined oxidation-reduction peaks. Compared with the only methylene blue modified electrode, the reduction peak of nanocomposite modified electrode has been increased, and oxidation peak current decreased, suggesting the special function of carbon nanotubes-methylene nanocomposite on the surface of electrode. Moreover, the experimental result showed that the catalytic ability of current modified electrode to substrate compound hydrogen peroxide. The Km of catalytic reaction reached to 3.56mmol/L, detection limit was1.0μmol/L. In addition, the probable interference co-existed under physiological conditions in the solution such as ascorbic acid, cystemine didn't produce obvious effects for determination.Combination with the polymer and noble mental nanoparticle on the surface of carbon naotubes will widen the applying range of carbon nanotubes in the fabrication of biosensor, enhance the performance of biosensor. The carbon nanotubes doped with polymer and mental naoparticle was synthesized through adding the polyethyleimine. Not only the electrostatic properties of the nanocomposite surface have been changed, but the conducting properties of the carbon nanotubes were also enhanced. Based on the electrodeposition technique, the chitosan-prussian blue membrane was easily fabricated. Then, the carbon nanotubes-PEI-Au nanocomposites and glucose oxidase can be fabricated by the layer-by-layer technique. Thus, the glucose biosensor was constructed. The presence of carbon-nanotubes-PEI-Au effectively increased the immobilization amount of Glucose oxidase and assured the stability of inner Chitosan-Prussian blue layer. Finally, the fabricated biosensor can measure the glucose of human serum with high sensitivity.Furthermore, we have developed the alternate strategy of electrodeposition and self-assembly, and successively fabricated a multilayer, ordered and stable nanocomposites film. First, a layer of Prussian blue nanoparticles was deposited onto the surface of Au electrode. Due to negative charge of Prussian blue and positive charge of composites, the alternate assembly process was carried out feasibly based on electrostatic interaction as driving force. The experiment result confirmed the nanocomposites film was high ordered and functionalized. Furthermore, the stability of Prussian blue as electron mediator was enhanced and assured by multilayer structure. Moreover, the nanocomposites demonstrated the high catalytic ability to hydrogen peroxide as substrate. The detection limit was 80nmol/L, and the sensitivity was 2274 (μA/mmol/Lcm2), the response time is lower than 3 seconds, which implied satisfied performance of current fabricated multilayer.Through the alternate technique for electrodeposition and self-assembly, a novel immunosensor for the determination of CEA was also developed. The ordered growing mode of the multilayer film was confirmed by SEM and cyclic voltammetry. The present method effectively circumvented the drawbacks of one-step electrodeposition and illustrated the potential of this alternate strategy of electrodeposition and self-assembly in the construction of functional composite films. The resulting immunosensor demonstrated several advantages, including high sensitivity, a low detection limit and long-term stability. Moreover, the construction process was simple, and the reproducibility of the electrodes was satisfactory. Thus, the present work demonstrated the potential application of the strategy of alternate electrodeposition and self-assembly in the development of novel biosensors.