Elucidation of bio-molecule recognition using semiconductor surface and its application to bioelectronics

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In this study, we aimed at giving a function of molecule recognition to a semiconductor surface by forming structurally controlled organic thin film on it and by detecting adsorption state of biomolecules and supramolecules which adsorb onto it using infrared spectroscopy.We need to use heavy water as substitute for ordinary water because DNA, protein, and cells have IR absorption peaks at the same region as the scissors mode of ordinary water. We cannot use general database because of deuterium substituion reaction at part of fuction groups when heavy water is used. Thus, we made new one by comparing results of experimental IR spectra and an ab-initio calculation. We demonstrated (1) highly sensitive detection of DNA hybridization and (2) elucidation of hybridization of DNA immobilized on silicon surface. We found that hybridization reaction strongly influences the C=O stretching vibration mode of bases by comparing IR spectral changes with the ab-initio calculation. We established electrophoresis in a solution and confirmed that electrical potential effectively draws DNA molecules up to silicon surface to enhance its sensitivity. An IR spectrum of drawn DNA molecules differed from one of floating DNA. This spectral change is attributed to protonization of bases. For the first time, we found that electrochemically reaction near the electrode can induce this phenomenon which is a well-known reaction depending on pH of a DNA solution. We demonstrated (5) highly sensitive detection of DNA hybridization using a porous thin film such as porous alumina and porous silicon. Furthermore, we started developing a method of analyzing functions of cells and we observed "apotosis" which is well-known as a designed death using IR spectroscopy and we could trace chemical changes in a cell until it resulted in the cell death. We now promote this study.