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The Study Of Electrochemical DNA Sensor For Detection Of Mercury Ions

Posted on:2017-02-11Degree:MasterType:Thesis
Country:ChinaCandidate:N XuFull Text:PDF
GTID:2308330485457097Subject:Biomedical engineering
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Recently, heavy metal contamination in aquatic environment is increasingly more serious, which has made a great negative impact on human health and environment. As it is difficult to solve the problems of heavy-metal pollution, more efforts should be made to control it, and even nip it in the bud. Thus it is of great significance for ecosystem and human health to monitor heavy metal ions on site. With the development of sensor technology, microelectronic integration technique and DNA molecular technique, attentions of researchers were attracted to have developed novel sensors for in-situ and on-line heavy metals detection.In this paper, we developed an integrated three-electrode sensor based on microelectrode array (MEA) firstly. Using differential pulse stripping voltammetry (DPSV) techniques, the sensor could be used to analyze of Hg2+ quantitatively. And based on thymine-Hg2+-thymine (T-Hg2+-T) coordination chemistry, two electrochemical sensors were developed for mercury (II) detection, through electrochemical impedance spectroscopy (EIS) techniques. This biosensor showed a high selectivity and a low detection limit of Hg"+with a good reproducibility.The major work and innovative work of this paper are listed below:1) A novel electrochemical hybrid-type DNA biosensor is designed to detect Hg2+.The first one is hybrid-type DNA biosensor. The sensor consists of the probe DNA and the immobilized DNA which is immobilized on the electrode. Firstly, the immobilized DNA is immobilized on the electrode through Au-S bound. And then under certain conditions, the immobilized DNA can hybridize with the probe DNA. Because the probe DNA is rich in thymine bases, it can specifically bind with Hg2+and formed T-Hg2+-T complex. In the presence of Hg2+, the probe DNA separated from the fixed probe and the gold electrode surface, which thus caused the change of the electrochemical impedance. The results reveal that the sensor showed a sensitive response to Hg2+ in linear concentration ranges from lnM to lOnM, with the detection limit of 0.2 nM. For Hg2+ detection, this sensor showed a good reproducibility.2) A novel electrochemical "hairpin-like" ssDNA biosensor is designed to detect Hg2+The second is a "hairpin-like" ssDNA biosensor. The sensor is simple to prepare, only consists of a T-rich single-stranded DNA. And ssDNA can be immobilized on gold electrode surface as self-assembled monolayer, which is easier to operate. In the presence of Hg2+, the ssDNA can form "hairpin-like" structure by T-Hg2+-T mismatch. Using EIS techniques, the impedance changes of gold electrode can be detected before and after the Hg2+ is added, which provide a rapid quantitative analysis of Hg2+. The detection limit of the sensor is as low as 0.4nM and its linear range of Hg2+ concentration is from 2nM to 10nM. It also has a good reproducibility.By optimizing experimental parameters, such as the immobilizing time of ssDNA, the backfilling or co-immobilizing condition of MCH and hybridization temperature, not only the time required for detection is shortened, but also the quality of immobilized ssDNA and Hg2+ detection performance of the electrode surface is improved3) An integrated three-electrode electrochemical sensor based on microelectrode array (MEA) is developed.Based on microelectronic processing techniques, an integrated three-electrode electrochemical sensor based on microelectrode array (MEA) is developed. The sensor mainly consists of Au-MEA, Ag electrode and Pt electrode. Au-MEA is designed as the working electrode, Pt electrode is designed as the counter electrode, Ag electrode is designed as the reference electrode. Using DPSV, heavy metals, Hg2+ can be detected quantitatively.
Keywords/Search Tags:detection of heavy-metal mercury ions, DNA electrochemical biosensor, microelectrode array, T-Hg2+-T mismatch
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