Construction Of Novel Electrochemical Biosensors Based On Antibody And Aptamer

With the rapid development of life science, bio-analysis plays more and more vital roles in it. Electrochemical biosensors attract particular interests and have developed into one of the most important tools as they have excellent characteristics such as:multiple response mechanisms, high selectivity, high sensitivity, real-time detection and extensive analytes recognition. Pursuing stable molecular recognition system with high selectivity and sensitivity becomes the frontier in the area of electrochemical biosensing. In this thesis, several novel electrochemical biosensors have been developed based on specificity of antibody and aptamer, using nanomaterial, electrocatalytic techniques; and their application in analysis of real biochemical samples have been investigated.In chapter 2, a label-free electrochemical immunosensor for the detection of protein analytes without redox-active centers is for the first time developed based on the combination of gold nanoparticles and the mediated charge transport through the multilayer films that is related to an electrocatalytic process. Given the low detection limit, high sensitivity and selectivity, the success achieved here seems plausibly to serve as a significant step toward the development of versatile label-free immunoassay.In chapter 3, a novel on/off electronic nanoswitch is constructed based on the conformational change of DNA sequence with a single guanine (G)-rich stretch. A thiolated, amine-containing G-rich DNA sequence is immobilized on the surface of gold electrode and is then labeled with redox-active ferrocene molecules. The surface-confined DNA sequence is able to change its configuration between rigid tetramolecular G-quadruplex and flexible single-stranded structures. The large conformational change'enables the probes to perform an inchworm like extending-shrinking motion, which is reflected by the fluctuation in current intensity. Since potassium ion can specifically bind to G-quadruplex, using this reagentless reusable electrochemical sensing platform, the simple, rapid and selective detection of potassium ion can be accomplished without the use of exogenous reagents.