Advanced imaging for DNA analysis based on scanning near-field optical/atomic-force microscopy (SNOAM)

Scanning near-field optical/atomic-force microscopy (SNOAM) was first applied to detect fluorescence hybridization of DNA immobilized on nano-particle media. Hybridization can also be used to determine the sequence of unknown DNA. 100-nm in diameter of polystyrene sphere carboxylate was used as the nano-particle media. Template DNA including target sequence was chemically modified with animo group at the 5'-end of single-stranded DNA. Amine-coupling reaction made covalent bond between template DNA and carboxyl group on the surface of the media. Single-stranded DNA of specific base sequence labeled either fluorescent dye, that is used to detect the complementary base sequence by hybridization. Simultaneous imaging the colloidal particles showed us topography and near-field fluorescence images of them. All particles were observed in the topographic image, however, some particles were realized in the fluorescence image. This result indicated that fluorescent hybridized DNAs on the surface of the media were visualized specifically. High density arrays or integration of media is a fast and effective means of accessing the gene variation. However, in this study, detection of hybridized fluorescent DNA conjugated with particle is a major purpose rather than arrangement technique.