A novel strategy for dual-channel detection of metallothioneins and mercury based on the conformational switching of functional chimera aptamer

A novel strategy for dual-channel detection of metallothioneins (MTs) and Hg2+ has been proposed. In the absence of Hg2+, the functional chimera aptamer (FCA) designed can form an intact G-quadruplex with flexibility, which was demonstrated to have peroxidase-like activities upon hemin binding. In the presence of Hg2+, the formation of T-Hg2+-T complex results in the conformational switching of FCA, which lost the peroxidase-like activities and cannot catalyze the oxidation of ABTS by H2O2. Upon addition of MTs in this solution, MTs could interact with Hg2+ to form a MTs-Hg2+ complex, leading to the recovery of the G-quadruplex DNAzyme. The color and absorbance of the sensing system were also changed accordingly. In the optimizing condition, Delta A was directly proportional to the concentration ranging from 8.84 nM to 1.0 mu M for Hg2+, and 7.82 nM to 0.462 mu M for MTs with the detection limits of 2.65 nM and 2.34 nM, respectively. The proposed dual-channel method avoids the label steps in common methods, and allows direct analysis of the samples without costly instruments, and is reliable, inexpensive and sensitive. (C) 2015 Elsevier B.V. All rights reserved.