Cavitation-microstreaming-based lysis and DNA extraction using a laser-machined polycarbonate microfluidic chip

We for the first time present a microfluidic cavitation-microstreaming-based cell lysis and DNA extraction method. Chemical lysis and DNA extraction have been demonstrated in a microfluidic format but the performance is limited by ineffective mass transport due to low Reynolds number. Here we propose to employ cavitation microstreaming for enhancing chemical lysis and magnetic-bead-based dynamic solid phase extraction (dSPE) of DNA. Cavitation microstreaming condition is optimized by exciting a microfluidic chip at its flexural resonance frequency (f(r)) measured via electrical impedance spectroscopy. Strong circulatory flows around bubbles excited at f(r) yields vigorous agitation, allowing fast lysis, and DNA extraction and purification. The microfluidic device is rapidly fabricated using CO2-laser machining and solvent-assisted thermal bonding of polycarbonate (similar to 25 min). Laser cutting conditions are experimentally determined to achieve a clean sidewall for negligible nonspecific binding and minimal burrs for unobstructed bonding. Solvent exposure and thermal bonding conditions are also experimentally determined for a leakage-free device with excellent dimensional integrity. Our method, although not fully optimized, exhibits an excellent DNA extraction performance, compared to a commercial kit and previous microfluidic methods. High extraction efficiency (76.9 %) and purity (A260/A280 = 1.85) are achieved for a relatively short assay time (similar to 25 min). Notably, DNA from as few as 18 cells is successfully extracted even from a highly diluted cell sample (0.18 cells/mu l). PCR and electrophoresis results confirm the excellent quality of the extracted DNA. Considering these notable performances, and straightforward fabrication and operation, we anticipate our DNA extraction method will be widely used in microfluidic nucleic-acid analysis devices.