| Although Ru(bpy)32+/TPA system (TPA = tripropylamine) has played a crucial role in the development of Electrochemiluminescence (ECL) and its applications, much effort has been devoted to develop new ECL labels to improve the sensitivity. In fact, although many neutral Ir(III) complexes have been demonstrated to display high ECL efficiencies in organic solutions usually with a degree of efficiency much higher than Ru(bpy)32+, their applicative field has been restricted by their very poor water-solubility and lack of active group for biological labeling. DNA is one of important genetic material to the life and is in charge of storing genetic information transferring genetic information. Studies of its structure and function contribute to realize the essence of the phenomenon of life at the molecular level , which has important significance in the field of the modern life sciences and medicine.Tumors, one of the most threatening diseases of the human being, plays an essential role in modern medicine. In recent years, many assay methods and sensors as currently popular techniques are being developed for the detection of tumor-related biomarkers. In this work, several new ECL neutral tris-chelate iridium(III) complexes were synthesized , study their application in the construction of new DNA biosensor and cell detecting. The details are given as follows:In this work, several neutral tris-chelate iridium(III) complexes, which were prepared and their investigations of the structure, optical, and electrochemical properties are reported. Using tri-n-propylamine (TPA) as an oxidative-reductive co-reactant, their ECL properties were studied in acetonitrile (CH3CN) and mixed CH3CN/H2O (50:50, v/v) solutions, respectively. Meanwhile, the influencing factors of ECL efficiencies, including working electrode, pH, and surfactant were investigated. A remarkable ECL enhancement (up to about 13.5 times), in comparison with the commonly used Ru(bpy)32+ (2,2'-bipyridyl) ruthenium(Ⅲ), is observed from Ir(FPP)2(acac) (where FPP is 2-(4-fluorophenyl)-4-phenylpyridine, acac = acetylacetone) at Pt disk electrode. At the same time, an increase in ECL efficiency is also observed in surfactant media. This study provided a new method for further improving and tuning the ECL efficiency by designing new iridium complexes with the appropriate cyclometalated or ancillary ligands.A new Ir complex was synthesized, its UV-vis absorption, fluorescence, electrochemistry and ECL characteristics were explored. Recently, circular amplifications based on DNA polymerase and endonuclease were confirmed that they were effective means for improving sensitivity. Encouraged by the above experiment results and to demonstrate the generality of Ir complex as a luminescent reagent, the above developed nanoprobe was designed to construct a protocol based on strand-displacement DNA polymerization and nicking endonuclease assisted cycle。The detection limit of 8.2×10?17 M could be estimated by using 3σruler, which is one of the most sensitive methods for detection and analysis of DNA to the best of our knowledge. Also, a simultaneous control experiment was carried out by labeling with Ru complex. The detection limit of 9.7×10?15 M was calculated according to 3σ. It is obvious that the sensitivity of the proposed protocol is improved 2 orders of magnitude by replacing conventional Ru complex. To further reveal the difference in sensitivity of biosensor between employing Ir complex and Ru complex label, the ECL responses of the biosensor with the same concentration of target DNA were tested. It could be found that, in the presence of the same concentration of target DNA, the ECL signal labeled with Ir complex is about 200 times higher than that based on Ru complex. It was found there was no matrix effect on the responses of detection when added blood is less than 6% in volume。However, a significant decrease of the signal was observed after adding more than 8% of blood. Herefore, 6% of human blood in volume was used in the following experiments. The study has presented a new luminescence labeling reagent for ECL, and it has been successfully applied to construct ultrasensitive biosensor. More importantly, base on the reagent, the sensitivity of biosensor for target DNA detection is improved more than 200 times compared to that employing the well-known ECL reagent Ru complex. As evidenced by our research, this assay allows us to determine cancer cell down to 6 cells and exhibits a significant specificity for Ramos even in 6% real human blood sample. It is expected that the easily synthetic, air-stable and very efficient phosphorescent emitter can be used in more fields for biological assays and clinical diagnoses. |
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