DNA hybridization detection by electrochemical impedance spectroscopy using interdigitated gold nanoelectrodes

A DNA biosensor is presented that is based on gold interdigitated nanoelectrodes of 100 nm width and 250 nm pitch. A single-strand oligonucleotide acts as the capture probe. Because of its nanometer dimensions, the device shows improved sensitivity when compared to similar systems. This encouraged us to perform a direct and unlabelled detection. After incubation with the DNA target, the impedance spectrum was recorded between 1 kHz and 10 MHz to obtain the net capacitance change. The use of a biotinylated DNA signalling probe permitted the integration of an amplification stage in a sandwich format that employs streptavidin-modified gold nanoparticles. The strategy was preliminarily tested by detecting the breast cancer related BRCA1 gene, where the noncomplementary, wild and mutated forms were easily differentiated at a concentration level of 3 μM (corresponding to a 30 pmol quantity).