Download Prof. Sabeth Verpoorte

Physikalisches Kolloquium
21. Juni 2004, 17:00 c.t., H6
Prof. Sabeth Verpoorte
Institute for Drug Exploration
University of Groningen
Though nucleic acid analysis has been a significant driver for development of the
microfluidics field, less attention has been paid to the integration of sample preparation into
these devices. Integrating operations such as DNA extraction, enrichment, and fragmentation
would facilitate the realization of truly integrated microsystems for DNA analysis. This paper
will describe work carried out recently in our lab exploring DNA sample handling in open
microchannels.
The preconcentration of DNA (48 kbp) has been demonstrated in open-channel devices.
Micro recirculating flows (RF) can be generated at low Reynolds number (Re < 0.01) by
opposing electro-osmotic (EOF) and pressure-driven flows (PF) in a device with divergent
and convergent elements. It was observed that charged polystyrene beads could be trapped in
RF. Furthermore, the electrokinetic mobility, ek, of the beads strongly influenced the
electric field (E) and pressure (P) conditions under which trapping occurred. This study
investigated the E and P conditions required to accomplish trapping of DNA using RF in
glass devices. It is proposed that RF could be used to extract DNA from mixtures containing
other substances, since DNA could be selectively trapped and concentrated under conditions
where other substances, like proteins, would flow out of the trapping channel.
Fragmentation of genomic λDNA down to an average size of 1500 bp using shear forces has
also been demonstrated. DNA samples were pumped through channels with narrow flow
constrictions to accelerate fluid flows at these elements. The DNA molecules are subjected to
stress in the resulting force fields, causing them to uncoil and fracture. Average fragment size
decreased as constriction width was reduced. The fragmentation process took only a few
seconds. A better understanding of this type of process will certainly aid in the eventual
development of useful analytical microsystems for cheap, fast DNA analysis.