Target-mediated base-mismatch initiation of non-enzymatic signal amplification network for highly sensitive sensing of Hg2+
Because of its adverse environmental effects, the establishment of convenient methods for monitoring Hg2+ with ultrahigh sensitivity is important to human health. With a new target-mediated base-mismatch initiation of signal amplification network strategy, we describe the development of a simple fluorescent sensing approach for detecting Hg2+ in water samples with high sensitivity. The assistant DNA probes trigger catalytic hairpin assembly (CHA) of two elaborately designed hairpins for the formation of many Mg2+-dependent DNAzymes via T-Hg2+-T base mismatch hybridization. Subsequently, the fluorescently quenched signal probes are cyclically cleaved by these DNAzymes to recover fluorescence and to release lots of secondary target sequences, which synchronously trigger CHA of the two hairpins to form the signal amplification network to yield drastically enhanced fluorescence for detecting Hg2+ with high sensitivity at 7.9 pM. Moreover, two mismatched bases are incorporated into the hairpin probes to reduce the background noise to further enhance sensitivity. The developed sensing method exhibits excellent selectivity toward Hg2+ and works well for real water samples. The successful implementation of our amplification strategy for the detection of Hg2+ can make such sensing method a non-enzymatic and convenient signal amplification means for detecting other biomolecules.