A chronocoulometric DNA sensor based on screen-printed electrode doped with ionic liquid and polyaniline nanotubes.

A chronocoulometric DNA sensor was constructed based on doped screen-printed electrode (SPE). Polyaniline nanotubes (PANINTs) and ionic liquid (IL) [C12mim][PF6] were doped into the commercial graphite ink (Electrodag 423SS) for the printing of the SPE, and chitosan was covered on the electrode surface. A homogeneous, stable and highly conductive electrode surface was thus obtained. A chronocoulometric DNA sensor was established based on this SPE. The target DNA sequences were specifically recognized by the capture probes immobilized on the SPE surface and the reporter probes labeled on reporter Au nanoparticles, which also carried bio-bar-code DNA sequences. The signals were generated through chronocoulometric interrogation of [Ru(NH3)6]3+ ions that bound to the DNA strands (mainly bio-bar-code DNAs) via electrostatic interactions. The target DNA could be quantitatively detected in the range from 1.0 x 10(-16) M to 1.0 x 10(-14) M, and a detection limit of 8.0 x 10(-17) M was found. Selectivity against three-mismatched DNA was found in this sensor.