Size Fractionation of Milliliter DNA Samples in Minutes Controlled by an Electric Field of 10 V

DNA size fractionation is an essential tool in molecular biology and is used to isolate targets in a mixture characterized by a broad molecular-weight distribution. Microfluidics was thought to provide the opportunity to create devices capable of enhancing and speeding up the classical fractionation processes. However, this conjecture met limited success due to the low mass or volume throughput of these technologies. We describe the mu LAF (mu-laboratory for DNA fractionation) technology for DNA size selection based on the stacking of molecules on films of similar to 100 mu m in thickness with 10(5) cm(-2 )pores similar to 2 mu m in diameter. Size selection is achieved by controlling the regime of electrohydrodynamic migration through the temporal modulation of an electric field. This technology allows the processing of milliliter-scale samples containing a DNA mass of several hundreds of ng within similar to 10 min and the selection of DNA in virtually any size window spanning 200 to 1000 bp. We demonstrate that one operation suffices to fractionate sheared genomic DNA in up to six fractions with collection efficiencies of similar to 20-40% and enrichment factors of similar to 1.5-3-fold. These performances compare favorably in terms of speed and versatility to those of the current standards.