Novel Electrochemical Detection Scheme for DNA Binding Interactions Using Monodispersed Reactivity of Silver Ions

This work demonstrates a label-free strategy for probing the interaction of DNA with small organic molecules. A solid-phase monolayer of silver deposited on a gold quartz-crystal electrode that is modified with DNA is used as the probe template. Results indicate that, by oxidizing the silver monolayer and in the presence of immobilized DNA molecules, highly reactive oxides of silver ions are generated in-situ, causing a change in the electronic properties of the immobilized dsDNA molecules. By scanning in the reverse direction, current is measured which is attributed to the reduction of the oxide layers. If a low molecular weight, organic DNA binding molecule is introduced into the medium, a structural change in the DNA may occur that is evidenced by a corresponding change in the redox properties of the silver monolayer. This ultimately presents a barrier to the interfacial charge transfer and related “site-blocking effects” of the organic molecules. The variation in the redox current is proportional to the concentration of the DNA binding molecule. The limit of detection was on the order of parts per trillion, which is remarkably lower than previously reported in the literature. Experimental evidence is provided from cyclic voltammetry, differential pulsed voltammetry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy.