Efficient fluorescence turn-on probe for zirconium via a target-triggered DNA molecular beacon strategy

Abstract

It is well-known that Zr 4+ could selectively bind with two phosphate-functionalized molecules through a coordinate covalent interaction to form a sandwich-structured complex (-PO 32--Zr 4+-PO 32--). In this paper, we for the first time converted such interaction into fluorescence sensing systems for Zr 4+ via a target-triggered DNA molecular beacon strategy. In the new designed sensing system, two phosphorylated and pyrene-labeled oligonucleotides were chosen as both recognition and reporter units, which will be linked by target Zr 4+ to form a hairpin structure and bring the two labeled pyrene molecules into close proximity, resulting in a "turn-on" excimer fluorescence signal. Moreover, γ-cyclodextrin was introduced to afford an amplified fluorescence signal and, therefore, provided an improved sensitivity for the target Zr 4+. This allows detection of Zr 4+ with high sensitivity (limit of detection, LOD = 200 nM) and excellent selectivity. The proposed sensing system has also been used for detection of Zr 4+ in river water samples with satisfactory result. © 2012 American Chemical Society.