switchSENSE® is a novel biophysical research technology that works with electrically actuated DNA nanolevers on chip-based gold microelectrodes. In brief, by alternating electric potentials applied to the gold microelectrode one can either attract or repel the negatively charged backbones of double stranded DNA nanolevers grafted to the sensor surface. This generates an oscillating orientation change of the DNA nanolevers, called switching. By observing the fluorescence emission of a fluorescent dye at the distal end of the DNA nanolevers, it is possible to assess the position of the DNA nanolevers relative to the gold surface. The intensity of the fluorescent light emitted by the dye reports on the distance to the gold surface due to a distance dependent radiation-free energy transfer to the gold. In other words, the closer the fluorophore is positioned to the quenching gold surface, the less light it emits. Thus, at positive (attractive) potentials, the DNA nanolevers align horizontally with the electrode’s surface, positioning the fluorescent dye close to the gold surface resulting in low fluorescence intensity. On reversing the electrode potential to a negative (repulsive) potential, the DNA nanolevers gradually move into an upright orientation, which is accompanied by a gradual increase of fluorescence intensity. A schematic of the DNA switching process is shown in Figure 1.

Figure 1: Alternating electric potentials either repel or attract surface grafted DNA nanolevers, which stimulates a voltage driven conformation switching. Due to the presence of the quenching gold surface, this switching can be observed using the fluorescence intensity of a dye that is attached to the distal end of the DNA nanolevers. At an upright orientation, the fluorophore exhibits the highest fluorescence intensity as the distance to the gold surface is maximum. For orientations of the DNA nanolevers closer to the gold surface, the emission is significantly decreased due to the enhanced quenching effect resulting from short gold/fluorophore distances.