A research group led by Prof. Chizuji Transom and Associate Prof. Masatoshi Taniguchi at the Institute of Industrial Science, Osaka University, has succeeded in identifying a molecule of the nucleic acid bases that make up DNA (Deoxyribonucleic Acid), using an electro-assay method. This method, which is completely different from the current DNA sequencing detection principle, has the advantages of being ultra-high-speed, label-free and low-cost, and is highly valuable for applications in fields such as customized personal medical treatment, precise searches for criminals, and ultra-high-speed testing for viruses. The paper was published in the online edition of Nature Nanotechnology. The development of medical drugs based on personal genetic information, the rapid apprehension of criminals based on precise DNA testing, and the ultra-high-speed and high-precision examination of influenza viruses require the development of rapid and low-cost DNA sequencing methods. The basic principle for realizing next-generation DNA sequencing is to configure nano-electrodes in nano-cavities and measure the arrangement of nucleic acid bases of a piece of DNA by electrodetection. But the development of the technology to recognize a molecule by electrophoresis is extremely difficult, and there have been no examples of validation of the principle.
The team used nanofabrication to create electrodes with a 1-nanometer electrode spacing, a method that can be controlled with a precision of 0.01 nanometers between nanoelectrodes. A molecule of a nucleic acid base was then sandwiched between the electrodes, and three nucleic acid base molecules were measured to show abnormal current values after being energized, proving that the type of nucleic acid base molecule can be identified in one molecular unit by electroassay. This method is the world's first successful verification of the basic principles of next-generation DNA sequencing.
The researchers placed nano-electrodes into four nucleic acid base molecules that make up elements of DNA, namely adenine, guanine, cytosine, and thymine, which were dissolved in aqueous solution. In measuring the time variation of the current between the electrodes, it was found that each of the three nucleic acid base molecules other than adenine had a different current value, and that different nucleic acid base molecules could be recognized based on the difference in current values. When two nucleic acid base molecules were mixed in equal amounts, the characteristic current peaks of the two nucleic acid base molecules could be observed, verifying that the corresponding nucleic acid base molecules could be recognized according to the current values.