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

Abstract

Hg²⁺ 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-Hg²⁺-T mismatch structure and the signal amplification of exonuclease III (Exo III) assisted target cycle, a fluorescent probe for facile and sensitive detection of Hg²⁺ 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-Hg²⁺-T pairs catalyzed by Exo III is prompted to happen upon recognition of trace Hg²⁺. Under the optimal reaction conditions, there is an excellent linear relationship between Hg²⁺ 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 Hg²⁺ 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.

Keywords: 2-Aminopurine; Aptamer; Exonuclease III; Mercury ions; Signal amplification.