Fabrication of microchambers defined by photopolymerized hydrogels and weirs within microfluidic systems: application...

This paper describes fabrication of serial microchamber arrays within the channels of a microfluidic device. The chambers are defined using a combination of weirs and UV-cross-linked hydrogel plugs (poly(ethylene glycol) diacrylates). This approach permits the microchambers to be addressed by pump-driven pressure in one dimension and by electrophoresis in the other. The function of the device is demonstrated by detecting DNA targets. Single-strand DNA (ssDNA) probes labeled with biotin were immobilized onto microbeads coated with streptavidin. The DNA-functionalized microbeads were packed into each of three microchambers by injection through inlet wells. Three oligonucleotides were designed as probes and four as targets. Hybridization reactions were performed by moving the targets across the array of probe-containing microchambers by electrophoresis. The hybridization of fluorescein-labeled ssDNA targets to complementary probes was observed by fluorescence microscopy. These studies resulted in four key observations: (1) there was no detectable binding of targets to noncomplementary probes; (2) hybridization was 90% complete within 1 min; (3) once captured, the targets could be independently released and recovered from the microbeads by treatment with 0.1 N NaOH; (4) multiple analyses could be performed using a single bead set, but there was degradation in performance after each capture/release cycle.