Microfluidic systems for DNA extraction, purification and concentration

由于遗传信息可以导致开发有效的治疗方法以改善人类健康，因此开发具有成本效益的全基因组测序方法非常重要。大多数生物分子，如蛋白质和DNA，都带有电荷，可以通过施加电场很容易地在流体中传输，这种现象被称为电泳。微流控技术基本上可以将化工厂缩小到几厘米的规模，并广泛用于基因组测序和绘图。然而，样品的制备仍然必须使用一个劳动密集型的过程，包括化学处理、洗涤和离心循环。微流体系统可以通过从蛋白质和其他细胞碎片中分离DNA来制备样品，这将比目前使用的技术更快、更便宜、更少出错。该研究项目结合了理论和实验研究，研究了在微流体装置中使用电场来捕获和分离细胞样本中的DNA所面临的挑战。当聚合物受到剪切流动时，它会拉伸并旋转以与流动成一定角度对齐。如果在与流体流动相反的方向上施加电场，带电的聚合物将垂直于电场的轴线迁移。这种作用在毛细管的横截面内产生了DNA的强烈不均匀分布，并且可以通过适当调整流场和电场来利用微流控装置捕获DNA。这种迁移是长而灵活的带电分子所特有的，而DNA是活细胞中唯一的这类分子。因此，DNA被困在装置内，而其他分子，如蛋白质，则通过。该提案旨在通过实验和数值模拟来验证多电解质迁移是由电诱导流动驱动的假设，从而更好地理解DNA（或其他多电解质）在流和电场联合作用下的迁移。该研究将确定在各种条件下横流迁移的大小，以优化用于全血样本DNA提取和浓度的微流控装置的设计。如果DNA可以成功地从裂解物中纯化出来，这将是在单个微流控芯片上集成样品制备和分析的重要一步。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.