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The purpose of the paper was to develop highly sensitive, fast, easy, affordable biosensor base on the specificity of antigen-antibody recognization. Several new bio-sensor technologies based on electrochemical technology were established by self-assembly and electrostatic adsorption. The dichlorophenoxyacefic acid (2,4-D) can be detected accurately, rapidly and conveniently by these technologies. The main results are shown as bellow:(1) A novel amperometric reagentless immunosensor has been constructed for the detection of 2,4-D. In this reagentless immunosensor,2,4-D was fixed on gold electrode surface which is modified by L-cysteine and the multi-layer horseradish peroxidase (HRP)/nano-Au. The results showed good linearity with the content of 2,4-D in the range of 5ng/mL-5000ng/mL.The linear equation is y=0.0199x+21.811, and the correlation coefficient R is 0.9968, with a detection limit at about 0.1ng/mL. This reagentless immunosensor, was found to be highly reproducible.In addition, no other electronic media and bio-molecular markers were used in this sensor.The detection results by using the sensor was found to be consistant with HPLC results.(2) The impedance reagentless immunosensor for the detection of 2,4-D was also studied. This method is realized mainly through porous nano-gold modified layer directly fixed 2,4-D antibody, which is formed by electro-deposition nano gold in the glassy carbon electrode surface. The results showed good linearity with the content of 2,4-D in the range of 0.5ng/mL-5000 ng/mL.The linear equation is y=0.045x+62.55, and the correlation coefficient R is 0.9970, with a detection limit at about 0.1ng/mL. This method is different from other immunosensors, because it can directly obtain the 2,4-D concentration information through the impedance changes. No antigen or antibody tags were needed in the sensor. Therefore, the interference was reduced.(3) A novel free competition immunosensor for the detection of 2,4-D was developed.2,4-D-BSA fixed upon gold electrode surface which is modified by self-assembly 1,6-F 2 Mercaptans and electrostatic adsorption nano-Au, and highly-specific competition immune response on electrode surface. The detection sensitivity was improved by using HRP labeled goat anti-mouse IgG to enlarge the signal. The results showed good linearity with the content of 2,4-D in the range of 0.5ng/mL-2500ng/mL.The calibration curve is y=-18.45x+71.59,and the correlation coefficient R is 0.9960, with a detection limit at about 0.05ng/mL.
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