Label-Free Femtomolar Detection of Target DNA by Impedimetric DNA Sensor Based on Poly(pyrrole-nitrilotriacetic acid) Film

An ultrahigh performance impedimetric DNA sensor is presented showing detection limits in the femtomolar range. This electrochemical setup was constructed initially by electrogeneration of poly(11-pyrrol-1-yl-undecanoic acid N alpha-,N-alpha-bis(carboxymethyl)-L-lysine amide) (poly-(pyrrole-NTA)) film. The latter was then modified by the coordination Of Cu2+ ions onto the chelating NTA centers followed by the immobilization of the ssHIV-DNA previously modified by a polyhistidine tag by affinity, binding. The immobilization of the DNA probe and hybridization with the complementary target ssHIV-DNA were investigated using fluorescence microscopy and quantified with quartz crystal microbalance experiments leading to DNA probe and duplex coverage of 1.7 x 10(-11) and 7.7 x 10(-12) mol cm(-2), respectively. The duplex formation was corroborated by amperometric measurements through the duplex labeling by a glucose oxidase. In the presence of hydroquinone as redox indicator, the DNA sensor was applied to the impedimetric detection of target DNA, without a labeling step. A linear quantification of the HIV DNA target was carried out in the range 10(-15) to 10(-8) mol L-1.