The Research Of Immunosensor Based On Electrostatic Absorption Immobilization Of Biomolecules

Electrochemical immunosensors are widely used for the assay of biological analytes. The advantages of this approach including their simple-design, high-sensitivity and low-cost attract substantial research efforts directed to the developments of some new electrochemical immunosensors in the last two decades. However, the method of immobilization, the prevention or elimination of nonspecific interactions, the reproducibility and the reusability still remain to be the key steps. The four parts of this thesis were all used electrostatic absorption to immobilizing biomolecules.1, Carrageenan which is the negatively charged natural polyelectrolyte, antibody is aggregated to the surface of the carrageenan-carbon paste electrode by electrostatic adsorption, such an immunosensor based on carrageenan-embedded in carbon paste electrode for transferrin assay has been constructed. The sensor exhibits a linear response to the transferrin in the concentration ranged from 1.5 μg mL-1 to 60 ug ml/-1, the regression equation can be expressed as follows:I = - 0.5146c + 59.06, correlation coefficient is 0.9960.2, It has been shown that gold nano-particles (colloid Au) can be used as a platform to immobilize antibodies by adsorption. Additionally, gold nano-particles can reduce the redox potential and catalyze the electrochemical redox reaction of some compounds on the electrode interface. Considering these characteristics of gold nano-particles, we designed a fluorescence immunosensor by immobilization of IgG antibody to a nano-Au monolayer modified chitosan-entrapped carbon paste. Using HPPA as substrate, HRP catalyze HPPA and form HPPA-dimer, which results in fluorescence increase of the substrate solution. The concentration of IgG antibody can be determined by fluorescence increase of HPPA-dimer. The sensor exhibits a linear response to IgG in the concentration ranged from 1.12 ng mL-1 to 24.8 μg mL-1, the regression equation can be expressed as: I = -69.04c + 133.5, correlation coefficient is 0.9800.3, In chapter IV, HRP was immobilized on electrode surface involving strong electrostatic absorption interaction between the enzyme and nano-zirconia dioxide. The concentration of H2O2 can be detected by determining the redox current of p-hydroquinone, which was oxidized by H2O2 in the presence of HRP. The linear response to hydrogen peroxide ranged from 3.6×10-6 to 7.2×10-3 mol L-1 was obtained.The equation can be expressed as: I = 8.488 × 10-4c + 0.4892, the correlation coefficient is 0.9960.4, Carrageenan, which is the negatively charged natural polyelectrolyte and HRP enzyme were entrapped in the carbon paste electrode, thus a strong-negatively enzyme electrode has been constructed. The concentration of H2O2 can be detected by determining the redox current of p-hydroquinone, which was oxidized by H2O2 in the presence of HRP. The sensor exhibits a linear response in the concentration ranged from 3.6×10-7 to 7.2×10-3 mol L-1. The regression equation can be expressed as: I = 2321c + 11.85, correlation coefficient is 0.9990.