Sensitive pseudobienzyme electrocatalytic DNA biosensor for mercury(II) ion by using the autonomously assembled hemin/G-quadruplex DNAzyme nanowires for signal amplification.

Herein, a novel sensitive pseudobienzyme electrocatalytic DNA biosensor was proposed for mercury ion (Hg(2+)) detection by using autonomously assembled hemin/G-quadruplex DNAzyme nanowires for signal amplification. Thiol functionalized capture DNA was firstly immobilized on a nano-Au modified glass carbon electrode (GCE). In presence of Hg(2+), the specific coordination between Hg(2+) and T could result in the assembly of primer DNA on the electrode, which successfully triggered the HCR to form the hemin/G-quadruplex DNAzyme nanowires with substantial redox probe thionine (Thi). In the electrolyte of PBS containing NADH, the hemin/G-quadruplex nanowires firstly acted as an NADH oxidase to assist the concomitant formation of H2O2 in the presence of dissolved O2. Then, with the redox probe Thi as electron mediator, the hemin/G-quadruplex nanowires acted as an HRP-mimicking DNAzyme that quickly bioelectrocatalyzed the reduction of produced H2O2, which finally led to a dramatically amplified electrochemical signal. This method has demonstrated a high sensitivity of Hg(2+) detection with the dynamic concentration range spanning from 1.0 ng L(-1) to 10 mg L(-1) Hg(2+) and a detection limit of 0.5 ng L(-1) (2.5 pM) at the 3Sblank level, and it also demonstrated excellent selectivity against other interferential metal ions.