The Electrochemical Biosensor Of Oligonucleotides

With the development of the society, people pay more and more attention to their health. This thesis forms new and effective electrochemical biosensors for the diagnosis of diseases.The first chapter introduces the main methods of electrochemical analysis and summarizes the development trend of the electrochemical biosensor.In the second chapter, a facile electrochemical DNA(E-DNA) sensor is developed for sensitive detection of DNA demethylase activity based on enzyme cleavage strategy. The E-DNA sensor is fabricated by a hemi-methylated stem-loop structure DNA with a terminus labeled with ferroceneacetic acid(FcA) as a signal reporter. The hemi-methylated DNA can be demethylated by demethylase and then recognized and cleaved by Bst UI endonuclease, which results in a significant decrease of voltammetric signal of FcA. Through the change of the electrochemical signal, the DNA demethylation level can be identified. Thus, it provides a useful platform for related molecular diagnostics and drug screening.In the third chapter, a triple signal amplification strategy is introduced to develop an electrochemical biosensor for highly sensitive miRNA-21 detection. In this protocol, the probe DNA is used as the miRNA recognizing unit, the DSN is used for the target cycling amplification,while the AuNPs and the HRP enzymatic catalysis signal amplification technique are used to enhance the sensitivity of detection. The triple signal amplification strategy generate significantly amplified amperometric currents variation value(Δi) for the detection of miRNA-21.In the fourth chapter, the GO-Fc nanocomposites are prepared, which show prominent electrocatalytic activity towards the oxidation and reduction of H2O2. The biosensor shows good stability, high sensitivity and selectivity which make it a promising candidate for the reliable and durable detection of H2O2.