Selective extraction of size-fractioned DNA samples in microfabricated electrophoresis devices.

We have designed and constructed a microfabricated device for separation of double-stranded DNA fragments using a crosslinked sieving medium and spatially selective extraction of the desired fraction. Based on measuring the width and spacing of migrating bands, a narrow side channel is constructed perpendicular to the separation channel to collect the DNA fragments of interest. This selective collection technique was tested using a 100 base pair double-stranded DNA ladder. We successfully demonstrate selective extraction of the desired fragment with minimal interference from the adjacent bands in an electric field of 31 V/cm. We also achieve extraction of multiple DNA fragments using an array of microelectrodes in this side channel. The device uses cross-linked polyacrylamide gel matrix, allowing the separation to be performed in a distance of 1 cm or less and at a low electric field strength. Together with on-chip electrode, this design is amenable to integration with reaction chambers into a single device for portable genetic-based analysis.