Sensitive DNA electrical detection based on interdigitated Al/Al2O3 microelectrodes

The detection of DNA by electrical based methods still faces the challenge of the low amounts of genetic material to be analyzed in order to make the assay useful for biological applications. In this work we present the possibility of detecting DNA strands by measuring a change of capacitance between interdigitated electrodes, of 1, 2 and 3 mum widths and spacing, made of aluminum fingers, coated with a thin alumina layer and constructed over an oxidized silicon wafer, reducing the non-specific precipitation of silver that occurs when using noble metal electrodes like gold. Labeling of DNA was performed by incorporation of biotinylated nucleotides and reaction with anti-biotin antibodies coupled to gold nanoparticles, whose size was increased by silver crystal precipitation. We observed a change in capacitance by a factor of at least two, using DNA solutions down to 0.2 nM, spotted on the electrodes. This method of detection thus appears compatible with the requirements of microarray technology and paves the way for further use in biological applications. (C) 2003 Elsevier B.V. All rights reserved.