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					Centrifugal (CD) Microfluidic Solid-Phase Extraction

Dane Van Domelen

Mentor: Professor Marc J. Madou

The BioMEMS research group at UC Irvine is developing microfluidic compact disks
(CDs) with specialized chambers, valves, and microchannels to automate rapid disease
detection. After the recent development of a cell lysis CD that efficiently extracts
cellular material from 70-µL blood samples, the focus has shifted to purifying target
DNA—in particular, the bacteria Group B Streptococcus (GBS). This research project
explores purification of GBS in clinical samples via solid-phase extraction, using large
functionalized beads (300 µm to 1200 µm in diameter). By introducing a sample
containing GBS ssDNA to functionalized beads, then rinsing to remove nonspecific
binding, and finally eluting the captured DNA to a separate detection chamber, GBS
DNA may be isolated and concentrated to detectable levels without employing PCR
amplification. Two CD designs were developed to test this hypothesis: a column CD, in
which the sample flows once through a column of tightly packed functionalized beads at
a rate that promotes maximum GBS capture; and a mixing CD, which mimics traditional
slow-tilt rotation by allowing continuous movement of the beads within the sample.
While the column and mixing CD designs have been optimized for flow rates (<4 µL/min
observed) and sample-bead interactions, respectively, preliminary testing has shown that
the beads excessively adsorb all types of DNA. As a result, further testing of the solid-
phase extraction CDs will be delayed until our collaborators at Université Laval improve
the surface chemistry of the beads and adequate DNA capture specificity is demonstrated.
Once the beads are ready, testing will reveal whether CD-based solid-phase extraction
provides sufficient GBS purification at realistic concentration levels.

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