DNA Purification of Biothreat Agents Using a Micropillar Chip

Processing large volume liquid samples for PCR-based infectious agent testing is ubiquitous among a wide variety of environmental samples. A number of different extraction protocols and devices are available to purify the nucleic acids from these complex samples. However, most of these approaches are optimized for specific kinds of samples and typically involve benchtop equipment and highly skilled personnel. Among the most common purification techniques are those that utilize a combination of chaotropic agents and random surfaces of glass (packed beds of micro-beads, fibers, particles, etc.) in a simple disposable plastic device. As an alternative surface, we have exploited the glass-surface properties of oxidized single crystal silicon in high-surface-area microstructures for silicon oxide-mediated nucleic acid extraction, purification, and concentration from large volume samples. One particular microstructure, a silicon pillar chip, provides highly-ordered and controlled surface interactions. The high aspect ratio (∼40) of the pillars provides an immense surface area within a relatively small volume, thus allowing for the capability to concentrate nucleic acids by several orders of magnitude. Here, we report on the effectiveness of this microfluidic chip in processing Francisella DNA in wastewater. The flow-through properties of the microfluidic chip enabled the entire procedure to be automated by embedding the chip in a reusable microfluidic cassette.