The maturation of microchip technology coupled with traditional bioassays has led to recent advances in the field of bioanalytical analysis. Microfluidic devices, one such platform, offer analytical advantages for samples of low concentration and small sample volume due to directed, efficient mass transport of analytes through microfluidic networks. Although significant advances have been made in DNA detection using array devices, there exists a need for a high throughput, diagnostic DNA detection system. One such strategy is to incorporate a selective DNA screening element into a microfluidic device that takes advantage of the aforementioned attributes.

We describe here a method for immobilizing single-stranded DNA (ss-DNA) probe molecules in polyacrylamide hydrogels within plastic microfluidic channels. The plugs are formed by photopolymerization of a solution containing 19:1 polyacrylamide/bisacrylamide and ss-DNA modified at the 5' end with an acrylic acid group. Short illumination times (5 min) are used, and spatial definition is achieved by the size and shape of the light source aperture. Fluorescent-tagged ss-DNA targets are driven through the hydrogel plugs using electrophoresis, and hybridize with complementary ss-DNA probes covalently bound in the hydrogel. The efficient hybridization of ss-DNA targets, coupled with the directed mass transfer associated with of the microchannel result in an effective selective detection element within a microfluidic channel.