Development of electrochemical telomerase assay aiming for cancer diagnosis in the early stage

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Telomere DNA, which is repeated sequence of TTAGGG existing in the termini of a human chromosome, is known to form an unique tetraplex structure. Artificial ligand, which can bind to such structural DNA and stabilized its structure, is an important in the view point of new anticancer drug. We found that ferrocenylnaphthalene diimide (FND) could bind to tetraplex DNA and stabilized its complex. Furthermore, we reveled that FND could be used for an electrochemical telomerase assay. This drove from the electrochemical detection of the selective concentration of FND on the telomere DNA extended by telomerase. In this study, we did the series of the experiments to obtain the detailed information of its binding manner for tetraplex DNA. The result suggested that this ligand could bind the tetraplex DNA through the stacking interaction with the upper or bottom of its three G-quartet planes. We also synthesized the series of the FND derivatives and evaluated their binding behaviors with tetraplex DNA. Their binding affinities were varied depending on their linker chains between the ferrocene and naphthalene diimide parts. These experiments were carried out in the presence of potassium ion as electrochemical experiment, where tetraplex structure was not determined unambiguously (Most recently, our experimental result and the previously papers suggested its unambiguous structure of hybrid type). We did the binding experiments in the presence of sodium ion, where tetraplex structure was determined as basket-type structure unambiguously and showed the similar binding behaviors in the case of potassium ion. To improve the binding affinity for tetraplex DNA, ferrocenylperylene diimide was newly synthesized and was studied on the binding with tetraplex DNA. These results obtained here should provide the information in the development of new tetraplex-selective ligand suitable for electrochemical telomerase assay.