Electrically contacted enzyme based on dual hairpin DNA structure and its application for amplified detection of Hg2+

In the present study, based on a dual hairpin DNA structure, a novel system of electrically contacted enzyme and its signal amplification for ultrasensitive detection of Hg2+ was demonstrated. In the presence of Hg2+, with the interaction of thymine–Hg2+–thymine (T–Hg2+–T), DNA sequence dully labeled with ferrocene (Fc) at 5′ end and horseradish peroxidase (HRP) at 3′ end, hybridized to the capture probe and formed the dual hairpin structure on the electrode. Fc unit acts as a relay that electrically contacts HRP with the electrode and activates the bioelectrocatalyzed reduction of H2O2. And based on the bioelectrocatalyzed signal amplification of the presented system, Hg2+ could be quantitatively detected in the range of 10−10–10−6 M with a low detection limit of 52 pM. And it also demonstrated excellent selectivity against other interferential metal ions.