Integrated analysis is now possible on a single chip (Credit: Robin Lui) Click image to magnify

A new microfluidic device that can perform sample preparation, polymerase chain reaction (PCR), and microarray detection functions on a single device has been developed by US researchers.

Robin Hui Liu, Jianing Yang, Ralf Lenigk, Justin Bonanno, and Piotr Grodzinski of the Microfluidics Laboratory, at Motorola Labs, in Tempe, Arizona, report in the April issue of Analytical Chemistry how they have attacked, what they call, the most challenging problems facing researchers developing microfluidic applications: on-chip sample preparation integrated with back-end DNA detection.

Most current microfluidic or microarray devices pursue single functionality and use purified DNA or homogeneous input samples. However, according to Liu, practical applications in clinical and environmental analysis require processing of samples as complex and heterogeneous as whole blood or contaminated environmental fluids. At present, sample preparation is carried out "off-chip" using conventional laboratory methods; this, however, results in something of an analytical bottleneck. Liu and his team wanted to utilize 'real' samples and so set about developing an integrated device.

An integrated chip could allow environmental samples to be analyzed in the field (Credit: David Bradley)

He and his colleagues have built a microfluidic device that can perform the whole front-end sample preparation steps; including target-cell capture using immunomagnetic beads, cell pre-concentration and purification, cell lysis, DNA amplification, and electrochemical detection of low abundance DNA. Samples as crude as blood can be studied with the automated device. Indeed, the system is entirely self-contained with no external pressure sources, fluid storage, mechanical pumps, or valves necessary for fluid manipulation, so sample contamination sources are eliminated, Liu explains.

The team demonstrated the utility of their device in the detection of pathogenic bacteria in up to millilitre whole blood samples and were able to carry out single-nucleotide polymorphism (SNP) analysis directly on diluted blood. "This is the first time that a fully integrated device has been demonstrated to perform the whole sample preparation, PCR, and DNA microarray detection from a complex biological sample such as whole blood," Liu told Reactive Reports.

Anal Chem, 2004, 76, 1824 - 1831; http://dx.doi.org/10.1021/ac0353029