Received on March 25, 2009
Accepted on August 28, 2009

Molecular Diagnostics and Genetics

Microsystem for Isolation of Fetal DNA from Maternal Plasma by Preparative Size Separation

¹ Fluidics & Simulation, Institut für Mikrotechnik Mainz GmbH, Mainz, Germany, and Nanobiotechnology and Bioanalysis Group, Department of Chemical Engineering, University of Rovira I Virgili, Tarragona, Spain
² Fluidics & Simulation, Institut für Mikrotechnik Mainz GmbH, Mainz, Germany
³ Nanobiotechnology and Bioanalysis Group, Department of Chemical Engineering, University of Rovira I Virgili, Tarragona, Spain, and Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain

^* To whom correspondence should be addressed. E-mail: drese{at}imm-mainz.de.

BACKGROUND: Routine prenatal diagnosis of chromosomal anomalies is based on invasive procedures, which carry a risk of approximately 1%–2% for loss of pregnancy. An alternative to these inherently invasive techniques is to isolate fetal DNA circulating in the pregnant mother's plasma. Free fetal DNA circulates in maternal plasma primarily as fragments of lengths <500 bp, with a majority being <300 bp. Separating these fragments by size facilitates an increase in the ratio of fetal to maternal DNA.

METHODS: We describe our development of a microsystem for the enrichment and isolation of cell-free fetal DNA from maternal plasma. The first step involves a high-volume extraction from large samples of maternal plasma. The resulting 80-μL eluate is introduced into a polymeric microsystem within which DNA is trapped and preconcentrated. This step is followed by a transient isotachophoresis step in which the sample stacks within a neighboring channel for subsequent size separation and is recovered via an outlet at the end of the channel.

RESULTS: Recovered fractions of fetal DNA were concentrated 4–8 times over those in preconcentration samples. With plasma samples from pregnant women, we detected the fetal SRY gene (sex determining region Y) exclusively in the fragment fraction of <500 bp, whereas a LEP gene (leptin) fragment was detected in both the shorter and longer recovery fractions.

CONCLUSIONS: The microdevice we have described has the potential to open new perspectives in noninvasive prenatal diagnosis by facilitating the isolation of fetal DNA from maternal plasma in an integrated, inexpensive, and easy-to-use microsystem.