Gene Detection by Light-to-electric Converting Intercalator and Its Application to DNA

在本研究中，我们发展了一种新的检测系统的DNA双链体使用光电转换。检测DNA双链体形成的原理如下。1)制备了单链DNA修饰的金电极。2)当双链DNA形成时，钌络合物将嵌入并将集中在电极表面。3)然后将可见光照射到电极上，观察到钌配合物激发产生的光电流。我们将多吡啶钌配合物负载DNA嵌入配体用于DNA检测。Ru（bpy）_3作为对照化合物。Ru（bpy）_2dppz作为钌配合物，带有DNA嵌入部分。此外，我们还合成了NDI-Ru_2作为插层剂负载钌配合物。将固定有DNA的金电极浸入含有光电转换插入剂Ru（bpy）_3、Ru（bpy）_2dppz、NDI-Ru_2的溶液中，用紫外分光光度法测定了插入剂Ru（bpy）_3、Ru（bpy）_2dppz、NDI-Ru_2的荧光强度。当可见光照射到电极表面时，在作为电子给体的叔胺存在下发生连续光电流。双链DNA形成后，Ru（bpy）_2dppz的光电流增加了36%，NDI-Ru_2的光电流增加了86%。这一结果表明，金属嵌入剂是通过其对DNA双链体的亲和力而富集在金电极表面的。在NDI-Ru_2的情况下，由于NDI作为电子受体，电子通过萘二酰亚胺从钌顺利地转移到金电极上。总之，我们可以区分双链和单链DNA之间的光电流的大小使用钌嵌入剂。

In this research we developed a novel detection system of DNA duplex using a light-to-electric conversion. The principle of the detection of DNA duplex formation is as follows. 1) The gold electrode modified by single stranded DNA was prepared. 2) When double stranded DNA is formed, ruthenium complex will intercalate and will be concentrated on the electrode surface. 3) Then the visible light is irradiated to the electrode, photocurrent caused by excitation of ruthenium complex will be observed.We used a polypyridyl ruthenium complex carrying DNA intercalating ligand for DNA detection. Ru(bpy)_3 was used as a control compound. Ru(bpy)_2dppz was used as a ruthenium complex carrying a DNA intercalating part. Furthermore, we synthesized NDI-Ru_2 as a threading intercalator carrying ruthenium complex. This type of compound has a smaller dissociation rate from DNA duplex, because it has threading intercalating part connected to two bulky groupsA DNA-immobilized gold electrode was dipped into the solution containing the light-to-electric converting intercalator (Ru(bpy)_3, Ru(bpy)_2dppz, NDI-Ru_2). When the visible light was irradiated to the surface of the electrode, continuous photocurrent occurred in the presence of tertiary amine as an electron donor. The amount of photocurrent increased by 36% in the case of Ru(bpy)_2dppz, 86% in the case of NDI-Ru_2 after the formation of double-stranded DNA. This result suggested that the metallointercalator was concentrated on the surface of gold electrode by its affinity to DNA duplex. In the case of NDI-Ru_2, we consider that electron was smoothly transferred from ruthenium to gold electrode through naphthalenediimide because NDI acts as an electron acceptor. In conclusion, we could discriminate between double stranded and single stranded DNA from the magnitude of the photocurrent using a ruthenium intercalator.