DNAzyme-guided polymerization of aniline for ultrasensitive electrochemical detection of nucleic acid with bio-bar codes-initiated rolling circle amplification

A novel and versatile amplified electrochemical strategy for ultrasensitive detection of nucleic acid has been developed on the basis of polyaniline (PANI) as the redox label which was guided and deposited by multiple HRP-mimicking DNAzyme as a powerful catalyst and template generated by bio-bar codes-initiated rolling circle amplification (RCA). The “sandwich-type” DNA biosensor was fabricated with the thiol-functionalized capture DNA first immobilized on an Au electrode and hybridized with one end of target DNA, the other end of which was recognized with a signal DNA probe that on the bio-bar codes, respectively. After the RCA reaction, multiple HRP-mimicking DNAzyme were successfully formed, which subsequently catalyzed the oxidation of aniline to PANI and lead to a readily measurable “turn-on” electrochemical signal. As a result of multiple amplification effects, the constructed platform exhibited a good linear response toward nucleic acid over a wide range of concentration from 6.0 fM to 1.0 nM.