Hybridization-Based Unquenching of DNA Hairpins on Au Surfaces:  Prototypical “Molecular Beacon” Biosensors

There is a keen interest in developing techniques for rapid genetic analysis that do not require labeling of an analyte. Here we demonstrate that fluorophore-tagged DNA hairpins attached to gold films can function as immobilized "molecular beacons". Two DNA hairpins incorporating portions of the Staphlococcus aureus FemA and mecR methicillin-resistance genes were attached to a gold substrate. Upon exposure to the complement, a approximately 26-fold increase in fluorescence intensity was measured corresponding to a 96 +/- 5% quenching efficiency. Studies with nonspecific DNA indicate that DNA hairpins immobilized on a gold surface retain their ability to bind complementary DNA sequences selectively.