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 (Hg2+) 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 Hg2+, the specific coordination between Hg2+ and T could result in the assembly of primer DNA on the electrode, which successfully triggered the HCR to form the hemin/Gquadruplex 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 O-2. 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 Hg2+ detection with the dynamic concentration range spanning from 1.0 ng L-1 to 10 mg L-1 Hg2+ and a detection limit of 0.5 ng L-1 (2.5 pM) at the 3S(blank) level, and it also demonstrated excellent selectivity against other interferential metal ions. (C) 2013 Elsevier B.V. All rights reserved.