Microfluidic systems for DNA extraction, purification and concentration

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Because genetic information can lead to the development of effective therapies to improve human health, it is important to develop methods for the cost-effective sequencing of an entire genome. Most biological molecules, such as proteins and DNA, carry a charge and can be readily transported through fluids by application of an electric field, a phenomenon known as electrophoresis. Microfluidic technologies can essentially miniaturize a chemical factory to the scale of a few centimeters and are widely used for genome sequencing and mapping. However, the samples still must be prepared using a labor-intensive process, involving cycles of chemical treatment, washing and centrifugation. A microfluidic system that could prepare samples by separating the DNA from proteins and other cellular debris would be faster, cheaper, and less error prone than currently used techniques. This research project combines theoretical and experimental investigations into the challenges involved in using electric fields within microfluidic devices to trap and separate DNA from cell samples. When a polymer is subjected to a shear flow, it stretches and rotates to align at an angle to the flow. If an electric field is then applied in the opposite direction to the fluid flow, a charged polymer will migrate perpendicular to the axis of the fields. This action creates a strongly inhomogeneous distribution of DNA within the cross section of a capillary tube, and it can be exploited to trap DNA within a microfluidic device by suitable tuning of the flow and electric fields. This migration is specific to long, flexible, and charged molecules, of which DNA is the only such class of molecules in living cells. Hence, DNA is trapped within the device, while other molecules, such as proteins, pass through. The proposal aims to develop a better understanding of DNA (or other polyelectrolyte) migration in combined flow and electric fields, by using experiments and numerical simulations to validate the hypothesis that polyelectrolyte migration is driven by electrically-induced flows. The research will determine the magnitude of the cross-stream migration under a wide variety of conditions to optimize the design of microfluidic devices for DNA extraction and concentration from samples of whole blood. If DNA can be successfully purified from the lysate, this will be an important step towards integrating sample preparation and analysis on a single microfluidic chip.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.