Electrical Detection of DNA Hybridization using Adjacent Impedance Probing (AIP) Method

Sensitivity and selectivity are two of the most challenging criteria for the development of DNA biosensor devices. These biosensor devices have attracted interest for the rapid identification of pathogens in humans, animals, and plants, for the detection of specific genes in animal and plant breeding and in the diagnosis of human genetic disorders. Traditionally, molecular diagnostic detection has relied on fluorescent or radioactive labels, and signal transduction is performed with equipment that greatly increases size and cost of the whole system. Electronic detection is expected to involve less complicated and smaller instrumentation while detection limits are maintained. Previous efforts on impedance-based DNA biosensors show limitations on repeatability, sensitivity and selectivity. In this work, we introduce the Adjacent Impedance Probing (AIP) technique for DNA hybridization detection. In this novel method, the DNA hybridization site is employed for the bio-recognition event (this site does not necessarily need an underlying conductor surface) and a bare adjacent conductor electrode is employed for generating the largest possible impedance change through the deposition of an insulating material or through chemical passivation induced by the enzymatic reporter reaction. The AIP approach dramatically increases the assay platform’s perfomance vs. the previously employed technique that integrates the impedance electrode and the DNA capture probes. In the case of AIP, the impedance of the bare electrode is lower than that of a conductor surface modified with a self-assembled monolayer (SAM) of probe molecules and will not be subject to the irreproducibility associated with fabrication of such a SAM layer; as a consequence the S/N ratio will increase. The novel detection scheme demonstrated in this work is expected to find real applications for fields in diagnostics and biowarfare agent detection.