Detection of microarray-hybridized oligonucleotides with magnetic beads.

The efficiency of hybridization analysis with oligonucleotide microarrays depends heavily on the method of detection. Conventional methods based on labeling nucleic acids with fluorescent, chemiluminescent, enzyme, or radioactive reporters suffer from a number of serious drawbacks which demand development of new detection techniques. Here, we report two new approaches for detection of hybridization with oligonucleotide microarrays employing magnetic beads as active labels. In the first method streptavidin-coated magnetic beads are used to discover biotin-labeled DNA molecules hybridized with arrayed oligonucleotide probes. In the second method biotin-labeled DNA molecules are bound first to the surface of magnetic beads and then hybridized with arrayed complementary strands on bead-array contacts. Using a simple low-power microscope with a dark-field illumination and a pair of complementary primers as a model hybridization system we evaluated sensitivity, speed, and cost of the new detection method and compared its performance with the detection techniques employing enzyme and fluorescent labels. It was shown that the detection of microarray-hybridized DNA with magnetic beads combines low cost with high speed and enhanced assay sensitivity, opening a new way to routine hybridization assays which do not require precise measurements of DNA concentration.