| Electrochemical immunosensor is a kind of biosenor combines electrochemical analysis with immunoassay. Electrochemical immunosensor has strong specificity, high sensitivity, and has very extensive application in the medical, environmental, food, agriculture and other fileds. The principle of electrochemical immunosensor is similar with traditional immunoassay methods; they are both immobilized the antigen or antibody by physical or chemical method to an interface, with direct or indirect method to detect the target antibody or antigea Prostate specific antigen (PSA) is a kind of serine protease, which is the main biomarker of prostate cancer. In normal serum PS A is commonly less than 4 ng/mL. When the concentration is greater than 10 ng/mL, it can be used as an important factor for diagnosis of prostate cancer. Therefore the ultrasensitive detection for PSA has very important significance in the early detection and diagnosis of prostate cancer. Disperse orange 1 (DO1) is one kind of disperse dyes, disperse dyes is a kind of industrial dye, mainly including azo, anthraquinone and heterocyclic type. The solubility of disperse dyes in water is very small, people need to use dispersing agents to make it form a uniform dispersion and with the chromaticity of dye. If the dyeing fectory do not properly handled the disperse dyes and let make flow into natural water, it can cause huge damages to the aquatic organisms and human body. So the detection of disperse dyes in water has big significance for the environment and the organism. Through electrochemical immunosensor, we can achieve the highly sensitive detection of the above two substances, and it can be extended to the detection of other big and small molecules. It is visible that electrochemical immunosensor has huge potential in modern analytical testing and diverse applications.The main content of this thesis including the following two aspects:(1) We built an amperometric type immunosensor based on multi-walled carbon nanotubes and gold nanoparticle conjugates for the highly sensitive detection of PSA. We first grafted a layer of 1,7-diaminoheptane as a mediation layer on a glassy carbon electrode surface, and then assembled the carboxyl multi-walled carbon nanotubes on the electrode through carboxamide reaction. Because the antibodies have amino groups too, we can use the carboxamide reaction to connect antibodies with multi-walled carbon nanotubes. The signal molecule of the immunosensor is gold nanoparticles conjugated with secondary antibody and 6-ferrocenyl hexanethiol. Gold nanoparticles not only have strong electrical conductivity which can accelerate the electron transfer, but also have large specific surface area that can load plenty of secondary antibody and signal molecules. Carbon nanotubes also have strong signal amplification properity. Thus the stratergy can realize multiple electrochemical signal amplification for the highly sensitive detection of prostate specific antigen.(2) We used impedimetric electrochemical immunosensor for the highly sensitive detection of disperse dye orange 1 (DO1). Firstly we grafted a layer of 1, 7-diaminoheptane on a bare glassy carbon electrode, and then immobilized the anti-DO1 on the electrode surface through carboxamide reaction. Since the antibodies can block of the electron transfer, the electrochemical impedance of the electrode surface increases. When there was target disperse orange 1 in the solution, the electrochemical impedance values would further increase. In addition, a further advantage of this strategy is that the antibodies immobilized on the electrode through carboxamide reaction are in a certain direction, which is superior to other ways through static adsorption method result in randomness direction of antibodies and reduce the efficiency of the immunological recognition. This method can be further extended to the determination of other disperse dyes. |
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