Study On Novel Electrochemical Biosensing Technology Based On Homogeneous Reaction

Recently, food hygiene and safety and the detection of toxins has gradually become a hot issue. So far detection technologies with high sensitivity for the detection of food mycotoxins is in urgent needs in order to guarantee food safety. In order to solve some prombles existed in the traditional biosensing techniques, such as high cost, low sensitivity, and complex operation, two novel electrochemical detection methods have been developed for selective and sensitive detection of toxins in food based on the advantages of the label-free homogeneous solution reaction and high specificity of aptamers. The main contents are as follows:(1) In chapter 2, a novel electrochemical aptasensor has been designed for the detection of AFB1 ( aflatoxin B1),this sensor realizes electrochemical detection of AFB 1 in a homogeneous solution,with sensing signals amplified by an Exonuclease I-based target recycling strategy. In the presence of analyte AFB1,the formation of aptamer-AFB1 complex would result in not only the dissociation of aptamer from the double-strand DNA but also the digestion process of cleaving the released Fc-labeled DNA into mononucleotides by exonuclease I, the cleaved Fc-labeled mononucleotide diffuses easily to the negative ITO electrode,generating an increased electrochemical signal.(2) In chapter 3, based on the integration of "signal on/off" and"labeling/label-free" strategies, another novel electrochemical aptasensor for multiple toxins analysis has been proposed. Two types of toxin-related oligonucleotides were immobilized on the Au electrode surface via self-assembly of the terminal thiol moiety, they could provide "turn on"signal through the DNA conformational changes resulted from target binding with aptamer. In the developed strategy, the stabilized dsDNA cannot bind to the electrode surface, whereas in the presence of toxins,the dissociation of the stabilized dsDNA conformational leads to the generation of signal indicator labeled single stranded DNA as a readout signal for the sensing events.This strategy has been demonstrated to exhibit good selectivity, high sensitivity, low cost with a detection limit of 0.04ng/mL and 0.01ng/mL to OTA(ochratoxin A) and AFB1 respectively.