Rapid detection of DNA hybridization on surface plasmon resonance based microarrays

The detection of DNA hybridization in medical diagnostics ought to be rapid, sensitive and specific. A platform technology based on surface plasmon resonance (SPR) is presented. We use TOPAS^® chips with integrated optics and combined with microfluidics. Applying a nanoliter dispenser, thiol-modified single-stranded probe DNA (anti-tag) is deposited on the gold surface of the chips to create a DNA microarray. We fabricate chips with sufficiently high probe density, which is a key factor for DNA chips and can be controlled by adding MgCl₂ to the immobilization solution. This technology offers the possibility of detecting PCR products comprising a single-stranded tag sequence being complementary to an anti-tag sequence of immobilized probes on the microarray. Consequently, this universal platform can be applied for detection of DNA hybridization based on the tag/anti-tag system. We demonstrate detection of specific hybridization of different 300 base pairs-long PCR products by SPR within less than five minutes. We checked for expected cross hybridizations with seven base pairs-long sequences at different positions in the tag/anti-tag sequence. Depending on the distance to the sensor surface we could observe crosshybridization if the according complementary sequence part is more distant from the surface. The initial binding rates (response units/min) at different PCR product concentrations were determined. Within five minutes a PCR product concentration of 2.6 nM is sufficient for distinct detection without crosshybridizations.