We propose a novel detection method for a duplex formation of DNA on a solid substrate. In this method, DNA monolayers are prepared on a gold thin film, and then the substrate is treated by an etching process. Since the DNA monolayer can act as a resist layer, the thickness of the gold film in the regions covered by DNA monolayers is larger than that in the region without the monolayer. Furthermore, the difference in the resistance effect of ss- and ds-DNA monolayers induces the difference in the thickness of the gold thin film after the etching. The resistance effect of the ss-probe DNA monolayer increases as a result of the formation of a duplex with the target DNA. The sequence-specific hybridization adsorption of the target DNA can be detected visually by measuring the light transmittance of the gold film, or with the naked eye. Using this method, we succeeded in detecting two base pair mismatches in a 30-base pair nucleotide.
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