Extraction of DNA molecules using crossed field electrophoresis in micropillar array

Abstract

This thesis presents a DNA(Deoxyribose Nucleic Acid) extractor based on an electrophoresis using periodic crossed electric fields in a micropillar array. The DNA extractor immobilizes target DNA molecules in the micropillar array by adjusting the period of the crossed electric fields, thus providing a starting-point independent target DNA extraction method without separation time mornitoring process. DNA molecules longer than 20 kbp(kilo base pare) are reoriented in the micropillar array when the direction of the electric field is changed. The reorientation time, depending on the DNA molecule size, results in the size-dependent mobility of DNA molecules for a given electric field. Under the crossed field, the DNA molecules, whose reorientation time is longer than the period of the crossed field, are trapped in the micropillar array. The trapped DNA molecules are extracted after a given time interval. In the present study, we applied the electric fields, crossed at 120°, to the DNA molecules in the micropillar array distributed in 120° direction. The DNA extractor, having nanometer entropic barriers, was fabricated by micromachining processes. The velocity of three different DNA molecules has been measured at E=5V/0.8cm in the fabricated DNA extractor. This resulted in the reorientation times of 4.80±0.44sec, 7.12±0.75sec, and 9.88±0.30sec for λ DNA(48.5 kbp), DNA from micrococcus(115 kbp), and T4 DNA(169.8 kbp), respectively. We found that T4 DNA, whose reorientation time is approximately 10 seconds, cannot come out of the micropillar array when the crossed electric field of 5V/0.8cm is applied alternately at a 10 second interval. We have demonstrated that the present DNA extractor separates DNA molecules longer than a critical value. This critical value can be adjusted by the magnitude and the period of the crossed electric field applied in the micropillar array.