| 1. Amperometric Detection of Glucose with Glucose Oxidase Immobilized in alginateAlginate (ALG), have been demonstrated as attractive material for the immobilization of biomolecules onto physical transducers, due to their hydrophilic, swelling, and porosity properties. A biosensor has been prepared with N ,N—Dimethylformamide(DMF) and alginate(ALG) as immobilization matrix. The influence of concentration of ALG and the thickness of membrane and quantity of the enzyme to the biosensor response have been discussed in detail. Amperometric Detection of Glucose with an unmediated sensor at 0.6V (vs.SCE) results in a rapid response, a wide linear range of 5×10-6 1×10-2 M, as well as good operational stability. The results indicated that the apparent Michaelis-Menten constant (KMapp) for the sensor was found to be 6.37 mM and the activation energy for enzymatic reaction is calculated to be 24.8 kJ mol-1.In addition, effects of pH value, applied potential, temperature and electrode construction were investigated and discussed.2. Electrochemical study of alginate modified layered double hydroxides composite matrix: Potential application in the development of amperometric biosensorsA new type of amperometric glucose biosensor based on alginate/layered double hydroxides organic-inorganic composite film was described. This hybrid material combined the advantages of organic biopolymer, alginate, and inorganic layered double hydroxides. Glucose oxidase (GOD) immobilized in the material maintained its activity well as the usage of glutaraldehyde was avoided. The composite films have been characterized by Fourier transform infrared (FT-IR). The results indicated that GOD retained the essential feature of its native structure in the composite film. The enzyme electrode provided a linear response to glucose over a concentration range of 1×10-5 - 2×10-3 M with a sensitivity of 70 mA M-1 cm-2 and a detection limit of 1μM based on S/N=3. Furthermore, the biosensor exhibited excellent long-term stability, and satisfactory reproducibility.3. Studies on direct electron transfer and biocatalytic properties of hemoglobin in poly(acrylonitrile-co-acrylic acid) matrixHemoglobin (Hb) immobilized in poly(acrylonitrile-co-acrylic acid), a new type of biologic film was achieved. The Hb/PAA-co-PAN film exhibited a pair of well-defined and quasi-reversible cyclic voltammetric peaks for Hb Fe(III)/Fe(II) redox couple in a pH 7.0 phosphate buffer. The formal potential of Hb heme Fe(III)/Fe(II) couple varied linearly with the increase of pH in the range of 4.0-8.0 with a slope of -53.5 mV pH-1, which implied that a proton transfer is accompanied with each electron transfer in the electrochemical reaction. Position of Soret absorption band of Hb/PAA-co-PAN film suggested that the Hb kept its secondary structure similar to its native state in the PAA-co-PAN matrix. The Hb in PAA-co-PAN matrix was act as a biologic catalyst to catalyze reduction of hydrogen peroxide. The electrocatalytic response showed a linear dependence on the H2O2 concentration ranging from 5×10-5～2.1×10-3M with a detection limit of 5×10-5M at 3 . |
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