Label-free electrochemical detection of DNA using ferrocene-containing cationic polythiophene and PNA probes on nanogold modified electrodes

A label-free electrochemical method for the detection of DNA–PNA hybridization using a water-soluble, ferrocene-functionalized polythiophene transducer and single-stranded PNA probes on the nanogold modified electrode is investigated. Nanogold modified electrodes can largely increase the immobilization amount of ss-PNA capture probe and lead to an increase of the electrical signal. The ferrocene-containing cationic polythiophene do not interact electrostatically with the PNA probes due to the absence of the anionic phosphate groups on the PNA probes. But after DNA–PNA hybridization, cationic polythiophene is adsorbed on the DNA backbone, giving a clear hybridization detection signal in differential pulse voltammetry (DPV). Very good discrimination against non-complementary DNA and four-base mismatch DNA is observed. These studies show that the proposed method can provide an alternative for expanding the range of detection methods available for DNA hybridization.