Fabrication And Applications Of Glucose And Catechol Biosensors

Biosensor is based on biological recognition units for the main function of the device. The recognition units can identify material of the specific target, and then converts the perception into the recognizable device signal through the special transducer. Biological recognition unit is similar to our human's sensory organs, it can perceive the things around directly, but can not express perception as the specific signal, while the transducer is precisely plays the role as converting the direct perception into recognizable signals. Biosensor is combined by chemical, biological, physical, and many other subjects'advanced technologies, and it has the features of simple operation, high sensitivity, high selectivity, fast analysis and so on. Now, biosensor is not only considered as a hot topic in analytical chemistry, but also has been very widely used in the food industry, environmental monitoring, clinical diagnostics and so on. In this article, we did not only discuss the preparation and application of chemically modified electrode, and the principle and purpose of enzyme and photochemical biosensor, but also did a lot of research for the topics of electrode selection, test methods and other subjects. We adopt some simple, innovative approach to construct catechol and glucose biosensor. Their structure and performances have been investigated by electrochemical characterization techniques such as electrochemical impedance spectroscopy (EIS), CVs in [Fe(CN)6]3-/4-, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), etc.The main points of this dissertation are summarized as follows:(1) We use the bare glassy carbon electrode as the substrate electrode, prepared polytaurine modified electrode by electrochemical polymerization, and then study the determination of catechol. Put the prepared glassy carbon electrode into to a PBS (pH 6.0, 0.1 mol/L) containing 2 mmol/L taurine, and then electropolymerized by cyclic voltammetry at the potential between -1.0 to +2.5 V, with the speed of 100 mV/s in for 8 cycles. The polytaurine film is formed on the surface of the GC electrode, and it shows strongly electrocatalytic affect to the oxidation of catechol. Compared with bare GCE, the peak of the current of polytaurine modified electrode increased remarkably and the△E decreased obviously. The response current of modified electrode to the catechol and the concentration of catechol linearly related at the concentration range between 5×10-6 to 9×10-4 mol/L, and the detection limit of 1.2μM. Furthermore, the proposed biosensor shows very good reproducibility and stability.(2) We used Cu(NO3)2 as the supporting electrolyte and the dendrite-like copper crystals which grow on the Indium-Tin Oxide (ITO) conductive glass as working electrode, thus building a glucose biosensor based on dendrite-like copper crystals nanometer modified electrode. Their structure and performances have been investigated by electrochemical characterization techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD). Dendrite-like copper crystals was constructed by electrochemically depositing onto the ITO conductive glass surface, with high density, uniform morphology; and has obvious secondary structure without containing other impurities. At the low potential, it shows strongly electrocatalytic oxidation performance to glucose. Under the optimal conditions, the response current of modified electrode to the glucose and the concentration of glucose linearly related at the concentration range between 0.05 mM to 0.8 mM, and the detection limit is 0.2μM. The glucose biosensor has the features of high sensitivity, good stability and reproducibility. This method had been tested for the determination of glucose in clinical serum samples, with satisfactory results.(3) Hydrogen peroxide was produced by enzymatic reaction of glucose oxidase and electrochemiluminescence (ECL) could be obtained by the reaction between luminol and hydrogen peroxide. Thus building a glucose biosensor that can determine the concentration of glucose fast and efficiently. Glucose oxidase is cross-linked by glutaraldehyde and BSA, and it is immobilized on MWCNTs modified electrode surface. The result shows that this method is not only able to immobilize GOx efficiently, but also has senitizing effect to the chemiluminescence system. MWCNTs enhanced the catalytic effect of enzyme in chemiluminescence reaction. Under the optimal conditions, a wide linear range of the propose biosensor for the detection of glucose was observed from 0.01 to 10 mM. The detection limit was found to be 5.0×10?6 M. The glucose biosensor has the features of fast response, high stability and reproducibility. This method had been tested for the determination of glucose in clinical serum samples, with satisfactory results.