Dual-channel detection of metallothioneins and mercury based on a mercury-mediated aptamer beacon using thymidine–mercury–thymidine complex as a quencher

Abstract

A novel dual-channel strategy for the detection of metallothioneins (MTs) and Hg2+ has been developed based on a mercury-mediated aptamer beacon (MAB) using thymidine–mercury–thymidine complex as a quencher for the first time. In the presence of Hg2+, the T-rich oligonucleotide with a 6-carboxyfluorescein (TRO-FAM) can form an aptamer beacon via the formation of T–Hg2+–T base pairs, which results in a fluorescence quenching of the sensing system owing to the fluorescence resonance energy transfer (FRET) from the fluorophore of FAM to the terminated T–Hg2+–T base pair. The addition of MTs into this solution leads to the disruption of the T–Hg2+–T complex, resulting in an increase of the fluorescent signal of the system. In the optimizing condition, ΔF was directly proportional to the concentrations ranging from 5.63nM to 0.275μM for MTs, and 14.2nM to 0.30μM for Hg2+ with the detection limits of 1.69nM and 4.28nM, respectively. The proposed dual-channel method avoids the label steps of a quencher in common molecular beacon strategies, without tedious procedure or the requirement of sophisticated equipment, and is rapid, inexpensive and sensitive.