High-resolution electrophoretic separation and integrated-waveguide excitation of fluorescent DNA molecules in a lab on a chip
Résumé
By applying integrated waveguide laser excitation to an optofluidic chip, fluorescently labeled DNA molecules of 12 or 17 different sizes are separated by capillary electrophoresis with high operating speed and low sample consumption of ~ 600 picoliters. When detecting the fluorescence signals of migrating DNA molecules with a photomultiplier tube, the limit of detection is as low as 2.1 picomolar. In the diagnostically relevant size range (~150-1000 base-pairs) the molecules are separated with reproducibly high sizing accuracy (> 99%) and the plug broadening follows Poissonian statistics. Variation of the power dependence of migration time on base-pair size - probably with temperature and condition of the sieving gel matrix - indicates that the capillary migration cannot be described by a simple physical law. Integrated waveguide excitation of a 12-µm narrow microfluidic segment provides a spatio-temporal resolution that would, in principle, allow for a 20-fold better accuracy than is currently supported by state-of-the-art electrophoretic separation in microchips, thereby demonstrating the potential of this integrated optical approach to fulfill the resolution demands of future electrophoretic microchips.
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