Preparation And Application Of Electrochemical DNA Biosensors With Signal Amplification

In recent years,electrochemical biosensors have been widely used in analytical chemistry,owing to their simplicity,low cost,fast response and high sensitivity.Taking advantage of DNA,such as diversity,assemblability,foldability,identifiability,electrochemical DNA biosensors not only can be used to detect the DNA damage and hybridization,but also can be used for the detection of proteins,DNA,RNA,small molecules,drugs and so on.However,with the development of analytical field,the concentrations of many target analytes that need to be tested are relatively very low,which needs for the ultrasensitive electrochemical DNA biosensors grow rapidly.So more and more people are committed to the development of a wide range of signal amplification technology,and they combined signal amplification method with electrochemical DNA biosensors to improve the detection ability of electrochemical DNA biosensors.In this thesis,we have developed several novel electrochemical DNA biosensors.We used a variety of methods to achieve the amplification of experimental signals for improve the performance of electrochemical DNA biosensors.The main works are summarized as follows:1.We briefly introduce the concept of sensor,electrochemical biosensor,the classification of electrochemical DNA biosensors,the importance of signal amplification method and the application of signal amplification method in electrochemical DNA biosensors.And we briefly summarizes the research content and significance of this thesis.2.We first report the use of a portable kind of personal glucose meter(PGM)combining a catalytic and molecular beacon(CAMB)system with a cation exchange reaction(CX reaction)for ultrasensitive PDGF-BB assay.It realized the amplification of the detection in three ways,including greater aptamer payload on nanoparticles,CX reaction releasing thousands of Zn2+ and the cycle by the catalyzing cleavage of 8-17 DNAzyme.In this experiment,signal produced by invertase can be detected by using personal glucose meter.Thus,we obtain a portable signal amplification method to detect PDGF-BB.3.In this work,a highly sensitive electrochemical DNA methyltransferase(MTase)activity assay was fabricated.We use DNA-gold nanoparticles(Au NPs)network as signal amplification unit and an easy assembly method by the linkage of benzenedithiol bridge.We introduce the method of DNA-gold nanostructure binding electrode by benzenedithiol to achieve sensitive detection of Dam MTase,which effectively avoids the complicated conditions of electrode and DNA solution.4.By combining advantages of catalyzed hairpin assembly and target DNA-mediated cycle amplification,we fabricated a sensitive electrochemical biosensor for detection of target DNA based on signal amplification.Generated by cycle amplification,the glucose oxidase modified Y type DNA structure transfer electron with carbon nanotube modified electrode produced electrochemical signals,realizing the sensor for sensitive detection of the target DNA.5.In this work,a novel signal on dual-signaling ratiometric electrochemical method was fabricated for fast and flexible detection of M.SssI methyltransfease(MTase)activity.In the presence of M.SssI MTase,catalytic methylation of hairpin DNA H1,which has led to ferrocene near the electrode surface and methylene blue away from the electrode surface,leads to the electrochemical signal changing to detect M.SssI MTase.