Excessive mercury ions have negative effects on individual health. So, it is of great significance to develop a method for rapid, sensitive and specific detection of Hg2+. In this study, the method for detection of Hg2+ was developed based on specific T-Hg-T mismatche and G-quadruplex. The template sequence mainly included the recognition region which could combine with Hg2+ specifically, the rich G region which could form G-quadruplex, and the speacer 18 partition zone. The target sequence mainly included 5' ends combining area and 3' end T-rich region. Templates and targets could be combined and the elongation was triggered only in the presence of Hg2+. Furthermore, the G-rich sequences were stripped off the templates and could form a single-stranded structure, because Spacer 18 had partition function. The G-quadruplex was formed with the K+and hemin, and catalyzed H2 O2-2,2-azinobis (3-ethylbenzothiozoline)-6-sulfonic acid(ABTS) reaction with color variations. The detection could be done within 35 min, and the Hg2+ concentration exhibited a linear correlation with absorbance at 414 nm within range of 20-500 nmol/ L, with a detection limit of 16. 5 nmol/ L (3σ). The recoveries of Hg2+ spiked in tap water were 98. 5％ - 103. 5％ . The method exhibited the advantages such as simple operation, low cost and short time, and operation value in emergency treatment and real-time environmental detection.

Functional nucleic acids are natural or artificialnucleic acid sequences with specific functions and special structures. Special metal ions are essential trace elements for human health, but excessive metal ions will be harmful to human health. The functional nucleic acids are widely used in the detection of metal ions because of their advantages such as easy modification, low price, high stability and strong specificity. This review describes the function of functional nucleic acid and metal ions, mainly including cutting type, link type, metal ion-mediated base pairing, click chemical type, conformation change type, and other types. Then, biosensor of functional nucleic acid combined with different signal output is introduced. Finally, the research significance and problems of functional nucleic acid in metal ion detection are discussed, and the future development direction and application prospect of functional nucleic acid biosensor are prospected.