Entropy-driven catalytic reaction-induced hairpin structure switching for fluorometric detection of uranyl ions.

An ultra-sensitive and "turn-on" method is demonstrated for the determination of uranyl ion. The assay is based on hairpin-to-DNAzyme structure switching that is induced by an entropy-driven catalytic reaction. An UO22+-specific DNAzyme is cleaved by UO22+ to produce a DNA fragment. This fragment initiates the entropy-driven catalytic reaction to produce a large number of a sequence "R". The sequence R initiates the circular cleavage of FAM-labeled hairpins by switching the hairpin to Mg2+-specific DNAzyme structure. This causes the recovery of green fluorescence. The method works in the 20 pM to 800 pM concentration range and the limit of detection is 4 pM. Graphical abstract Entropy driven catalytic reaction induced hairpin structure switching for fluorometric detection of uranyl ions.