Facile and sensitive detection of mercury ions based on fluorescent structure-switching aptamer probe and exonuclease Ⅲ-assisted signal amplification.

Hg is highly toxic to human health and ecosystem. In this work, based on the unique fluorescent property of 2-Aminopurine (2-AP), the formation of T-Hg-T mismatch structure and the signal amplification of exonuclease III (Exo III) assisted target cycle, a fluorescent probe for facile and sensitive detection of Hg is constructed. The hairpin-looped DNA probe is rationally designed with 2-AP embedded in the stem and thymine-rich recognition overhangs extended at the termini. The cleavage of the double stranded DNA stem with stable T-Hg-T pairs catalyzed by Exo III is prompted to happen upon recognition of trace Hg. Under the optimal reaction conditions, there is an excellent linear relationship between Hg concentration and fluorescence intensity in the range of 7.5-200 nM with a detection limit of 0.38 nM. In addition, the detection results of Hg in Songhua River water and fish samples are satisfactory. The fluorescent probe avoids labeling additional quenchers or quenching materials and has strong anti-interference ability. Thus, the fluorescent probe has a broad prospect in practical application.