Label-free capacitance DNA sensing

This paper presents the use of direct capacitance measurements for label free hybridization detection of ssDNA immobilized directly on a gold interdigitated array of microelectrodes (IDAM). Thiol modified 18 bases long Poly-dT ssDNA molecules were immobilized on the Au IDAM surface without the use of any isolative self assembled monolayer (SAM). Afterwards a Poly-dA ssDNA solution was deposited on the immobilization area to induce molecular hybridization. IDAM capacitance measurements were taken throughout the cleaning, immobilization and hybridization procedure to detect the presence of the immobilized ssDNA on the electrode surface and furthermore hybridization. Capacitance measurements using a potassium phosphate (KH₂PO₄ 0.1mM pH=9.9) electrolyte covering the electrode array demonstrate an increase of 5.837 pF and 8.409 pF after immobilization and hybridization respectively. These results provide a simple technique for transduction of bio-molecular identification which could potentially be applied for the identification of other biological markers.