Research On Electrochemical Detection Technology Based On DNA Probe

With the rapid development of genetic engineering, the conventional methods of analysis and detection has been unable to meet the current needs. Many new detection devices and analysis methods should be emerge as the times require, electrochemical DNA biosensor was one of them. The principle of electrochemical DNA biosensor is detected the molecular recognition process provided by DNA probe, followed by a transducer to measure the result of the conversion to the electrochemical signal can be identified.The detection of specific DNA fragments or small protein protein is very important in the diagnosis of gene related diseases, monitoring environment and military anti-terrorism. Study of electrochemical DNA biosensor is to meet the needs of high sensitivity detection, high selectivity detection and convenient and fast detection of specific DNA segments or small molecular proteins. In recent years, many kinds of sensing methods, which can be divided into acoustic sensors, optical sensors and electrochemical sensors, can be broadly divided into acoustic sensors, optical sensors and electrochemical sensors. Due to the characteristics of the electrochemical detection method has high sensitivity, low energy consumption, convenient and low cost. In recent years, electrochemical DNA biosensor become a very active research field and has been developing rapidly.In the present work we research the DNA biosensor systematically, which modified electrodes with the apter and DNA dendritic polymer, and for the detection of specific DNA sequences or 8- hydroxy- 2 '- deoxyguanosine. The details of my work as follows: 1. A label-free electrochemical aptasensor for 8-hydroxy-2 ?-deoxyguanosine detectionA label-free electrochemical aptasensor for the determination of 8-hydroxy-2-deoxyguanosine(8-OH-dG) was described here. This method was based on the conformational change of 8-OH-dG-aptamer(Apt) in the presence of 8-OH-dG. The G-rich Apt was self-assembled on the surface of gold electrode by Au-S bond. The assembly process of the aptasensor was characterized using cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS). The conformation of Apt changed fromflexible single stranded structures to compact G-quadruplex in the presence of 8-OH-dG, which hindered the negatively charged [Fe(CN)6]4- approach to the electrode. The switchable surface provided a sensing platform for the free-label detection of 8-OH-dG. Upon 8-OH-dG binding to the immobilized Apt, a significant decrease in the oxidation current of [Fe(CN)6]4- was observed due to the Apt conformational change. The aptasensor showed a detection limit of 0.315 nM and a wide linear range between 1.75 nM and 3.675?M for 8-OH-dG. The aptasensor displayed high stability as well as high specificity against uric acid, a strong interferent for the detection of 8-OH-dG. 2. Highly sensitive electrochemical biosensor based on nonlinear hybridization chain reaction for DNA detectionIn the present work we constructed an ultrasensitive detection platform for specific DNA based on nonlinear hybridization chain reaction(HCR) by triggering chain-branching growth of DNA dendrimers. HCR was initiated by target DNA(t DNA) and finally formed dendritic nanostructures by self-assembly. The electrochemical signal was drastically enhanced by capturing multiple catalytic peroxidase with high-ordered growth. Electrochemical signals were obtained by measuring the increase in reduction current of oxidized 3, 3?, 5, 5?-tetramethylbenzidine sulfate(TMB), which was generated by HRP in the presence of H2O2. This method exhibited ultrahigh sensitivity to tDNA with detection limits of 1.0 fM. Furthermore, the biosensor was also capable of discriminating single-nucleotide difference among concomitant DNA sequences. 3. Electrochemical biosensor based on nonlinear hybridization chain reaction for DNA detectionAs a result of horseradish oxidase(HRP) is influenced by the reaction temperature, We proposed an ultrasensitive detection platform for specific DNA based on nonlinear hybridization chain reaction(HCR) by triggering chain-branching growth of DNA dendrimers. HCR was initiated by target DNA(tDNA) and finally formed dendritic nanostructures by self-assembly. The electrochemical signal was drastically enhanced by capturing multiple RuHex with high-ordered growth. Electrochemical signals were obtained by measuring the increase in reduction current of RuHex. This method exhibited ultrahigh sensitivity to tDNA with detection limits of 0.33 fM. Furthermore, the biosensor was also capable of discriminating single-nucleotide difference among concomitant DNA sequences. 4. Electrochemiluminescence biosensor based on nonlinear hybridization chain reaction for DNA detectionWe demonstrated an ultrasensitive detection platform for specific DNA based on nonlinear hybridization chain reaction(HCR) by triggering chain-branching growth of DNA dendrimers. HCR was initiated by target DNA(tDNA) and finally formed dendritic nanostructures by self-assembly. Owing to multiple Electrochemical luminescence properties of pyridine ruthenium were captured on the DNA dendrimers, the electrochemiluminescence signal was drastically enhanced. This method exhibited ultrahigh sensitivity to tDNA with detection limits of 3.3 fM. Furthermore, the biosensor was also capable of discriminating single-nucleotide difference among concomitant DNA sequences.