Carbon Nanoparticles Luminol ECL System And Its Application In The Inhibition Of DNA Testing

Nucleic acid is the large molecules that contain genetic information of living organisms. It has a relatively complicated structure, so developing accurate and fast detection methods is an important research topic in the biology field. So far, all of DNA detection methods, polymerase chain reaction (PCR) and gene chip are on development of mature. But these two kinds of detect methods need expensive equipments and complex technology, which limit their wide applications. Therefore, a lot of DNA detect methods were developed based on DNA hybridization, mainly including fluorescence, chemiluminescence, electrochemistry and electrochemiluminescence.Electrochemiluminescence (ECL) is a technique that combines chemiluminescence and electrochemistry. The chemiluminescence reaction is initiated by an electrochemical reacton at electrode surface. Such an electro-initiated reaction introduces a large number of additional advantagges, such as wide linear range, high selectivity and sensity, good controllability, rapid and convenient operation, simple equipment, intersecting with many other subjects. At present, it has been widely used in biology, medical science, gene, immunoassay and environment, etc.In this paper, it was found that Cdots had an obvious inhibition effect on luminol electrochemiluminescence (ECL) system, maybe due to the electronic transfer between CDots and the excited state of luminol. It was also reported that single-stranded DNA (ssDNA) could be adsorbed on the CDots’s surface via π-π stacking interactions, while double-stranded DNA (dsDNA) did not possess this feature. Based on those findings, a simple and cheap DNA ECL detection system was developed.This thesis consists of two parts, review and research work. The first part is the review, mainly introducing the development, definition and analytical performance of ECL, the principle and application of luminol and Ru(bpy)32+ECL system, development and analytical methods of DNA sensors, analytical applications of nanomaterials in the ECL field, the synthesis and application of carbon nanoparticles, finally, the research purpose and significance of this paper.The research section contains two subunits.Subunit2.1, the investigation on immobilizatioin-free detection of DNA by luminol-carbon nanoparticles ECL system.Step pulse was used to trigger a luminol ECL reaction and Cdots had an obvious inhibition effect on it. It was further found that the inhibited luminol ECL signal by CDots was recovered by probe DNA. However, this ECL signal was decreased by hybridization. Under the optimal experimental conditions, the linear range of the proposed method for determination of DNA is2.5×10-12～1.0×10-10mol/L and the detection limits is1.8×10-13mol/L. The detection process is conducted in solution, so it did not need to label and immoblize DNA probe. The proposed method is simple and fast for the determination of DNA.Subunit2, study on DNA sensor based on luminol-carbon nanoparticles ECL system.Based on the detection system used in section2.1, we found that the ECL signal decreases with the increase of the concentration of target DNA. Therefore, in our this research work we immoblized probe DNA on the electrode surface and Cdots could be adsorbed on probe DNA via π-π stacking interactions, which led to the further decrease of inhibited ECL of luminol. However, with the addition of complementary DNA, the electrostatic repulsion between dsDNA and CDots made CDots keep away from the surface of electrode, which resulted in the increase of the inhibited luminol ECL signal. The linear range of the proposed method for determination of DNA is1.0×10-10～7.5×10-9mol/L and the detection limits is5.2×10-11mol/L. The sensing system can also be used to detect a long base sequence, such as the number of base sequence of DNA is45and55.This paper use DNA hybridization technology, inhibition effect of Cdots on luminol ECL and different inhibition effects between ssDNA and dsDNA, to establish two different detection methods for DNA. This does not only provide a new way for the fabrication of DNA sensor, but also realize the application of Cdots in the ECL field.