Rapid Label-free DNA Quantification by Multi-frequency Impedance Sensing on a Chip.

DNA quantification and characterization are of critical importance in disease diagnosis and clinical analysis, while label-free technology greatly simplifies the sensing protocol as it eliminates the extra step for attaching the indicator to DNA strands. In this work, we present a novel label-free DNA detection methodology based on electrical frequency-dependent impedance. The impedance of DNA strands conjunct with streptavidin-coated magnetic beads was measured at 8 different frequencies using an electrical impedance sensor integrated on a chip. Different concentrations of 300 bp double-stranded DNA samples were used to validate our sensor. The minimum DNA amount that could be successfully detected was 0.77 ng (3.9 amol). Detecting DNA fragments using our sensor could be further reduced from currently 20 minutes to under 15 minutes.