A simple and sensitive fluorescent sensing platform for Hg2+ ions assay based on G-quenching

In this work, a novel fluorescence biosensor was demonstrated for detection of Hg2+ ions with relatively high selectivity and sensitivity. The sensing scheme was based on G-quenching induced by Hg2+ ions. In the presence of Hg2+ ions, the single-stranded signal probe which has carboxylfluorescein (FAM) and guanine segment at its 5′ and 3′ ends, respectively, folded into duplex-like structure via the Hg2+-mediated coordination of T–Hg2+–T base pairs. It brought guannine segment close to the dye and caused a remarkable decrease of fluorescence signal. The sensor showed a sensitive response to Hg2+ ions in a concentration range from 0.5 to 10 μM, and a detection limit of 0.5 nM was given. This homogeneous system required only a single-labeled oligonucleotide, operated by concise procedures, and possessed comparable sensitivity as previous approaches. Furthermore, the sensor exhibits a great perspective for future practical applications.