A dynamic, ultra-sensitive and "turn-on" strategy for fluorescent detection of uranyl based on DNAzyme and entropy-driven amplification initiated circular cleavage amplification

A uranyl detection strategy with ultra-sensitivity was developed based on entropy-driven amplification and DNAzyme circular cleavage amplification. The cleavage of UO22+-specific DNAzyme produces a DNA fragment to initiate the entropy-driven amplification. Two DNA sequences released from the entropy-driven amplification are partly complementary. They can form an entire enzyme strand (E-DNA) of Mg2+-specific DNAzyme. The formed E-DNA can circularly cleave FAM-labeled probes on gold nanoparticles (AuNPs), causing the leaving of FAM from AuNPs and recovery of fluorescent signal. A linear relationship was obtained in the range from 30 pM to 5 nM between fluorescence intensity and concentration of UO22+. The limit of detection was low to 13 pM. This method showed a promising future for practical application in real water samples. (C) 2019 Elsevier B.V. All rights reserved.