| Biosensor is a novel and developing technique that linking biology,iatrology,physics, chemistry and electronic technology in recent years.It provides a sensitive and selective tool for the quantitative determination of analytes in various fields,such as clinical diagnostics,biotechnology, environmental protection,and food industry.The name biosensor is a device composed of a biological recognition element and a transducer.To design the biosensor,the crucial aspect is the deposition of biorecognition molecule,such as an enzyme,antibody(antigen),sequence of DNA,in high amounts with retention of their specific activity.At the same time,the selection of the suitable electroactive probes also deeply affects the performance of biosensor.In this thesis,the felicitous way of the immobilization of the biomolecules and the selection of the electroactive probes has been discussed and describled as follows:1.A novel glucose biosensor based on layer-by-layer(LBL) self-assembling of chitosan(CS) and glucose oxidase(GOD) on Prussian blue(PB) film has been studied.A cleaned gold electrode was first deposited with PB by applying a constant potential.Subsequently,GOD layer has been assembled alternately with CS layers,to construct the multilayer films of {GOD/CS} bilayers.The method was simple and controllable.Analytical conditions,such as the number of the {GOD/CS} bilayers,pH and applied potential were also investigated.The amperometric glucose biosensor showed a fast response time(within 10 s) and a linear calibration range from 6.0×10-6～1.6×10-3 mol/L with a detection limit of 3.1×10-6 mol/L for the detection of glucose(s/n=3).With the low operating potential,the glucose biosensor showed little interference to the possible interferents in the determination,including ascorbic acid,acetaminophen and uric acid,exhibiting an excellent selectivity.2.An effective electrochemical singnal amplification strategy based on polyaniline nanofibers (PANFs) and gold nanoparticles(GNPs) was proposed to amplify the electrochemical singnal of redox probe of thionine(Thi) adsorbed through electrostatic interaction on a nation(Nf) modified gold electrode,and the amplified electrochemical signal was designed to detect the concentration of carcinoembryonic antigen(CEA),as a model protein,in solution.The PANFs and GNPs construct a conductive layer,which was employed not only to enhance the electron transfer for the oxidation-reduction current signal amplification,but also to offer a high surface area and good biocompatibility for augmenting the immobilization density of carcinoembryonic antibody (anti-CEA) with well remained bioactivity.Different electrochemical signal amplification strategies were investigated as comparison,and the proposed method showed the best performance.The morphology of the PANFs was characterized by scanning electron microscope(SEM) and the good biocompatibility of the complex layer was proved by quartz crystal microbalance(QCM) experiment. The factors influencing the performance of the resulting immunosensor were studied in detail.Under optimal conditions,the proposed immunosensor exhibited a good electrochemical behavior to CEA in a concentration range from 0.1 to 120 ng/mL.3.A simple and effective method to shift the electroactivity of potyaniline(PANi) films to neutral pH conditons by electropolymerization of aniline in the presence of 3-mercaptopropanesulphonate(MPS) on Au electrodes.The electrochemical behavior and catalytic ability for the ascorbic acid in neutral solution was investigated by cyclic voltammetric method. Result indicates that the film shows very good stability and electroactivity in neutral solution.For further application,the stable electroactivity of the PANi/MPS film was design for the detecting of carcinoembryonic antigen(CEA),an important tumor marker,in solution.The factors influencing the performance of the resulting immunosensor were studied in detail.Under optimal conditions,the immunosensor was highly sensitive to CEA with a detection limit of 0.03 ng/mL(S/N=3) and the linear range with two concentration intermittences was from 0.05 to 10 ng/mL and from 10 to 120 ng/mL,respectively.
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