It is important to design new ways with high specificity and sensitivity to detect lead (II). Here, ‘8–17’ DNAzyme was used as a Pb 2+ -dependent probe with high sensibility and selectivity based on chemiluminescence (CL). When Pb 2+ was present, the substrate strand was cleaved and the active hemin/G-quadruplex DNAzyme structure was formed in the presence of another sequence which contained two parts, one could be complementary with part of the substrate strand and the other was a G rich subunit. The active hemin/G-quadruplex DNAzyme structure could catalyze luminol oxidation and quantitative analysis of Pb 2+ was carried out according to the CL of luminol. Results showed that CL intensity of luminol at 452 nm had a linear relation with the concentration of Pb 2+ in the range from 5 nM to 1 μM, and the limit of detection was 0.79 nM ( S / N = 3). This method was also used to detect the contents of Pb 2+ in lake water and tobacco and the results (62.4 ± 4.0 nM and 15.2 ± 2.2 nM, respectively) were extremely closed to those of inductively coupled plasma-mass spectrometry (ICP-MS) (57.0 ± 1.4 nM and 14.5 ± 0.91 nM, respectively).
Wang Junyang,Liu Zheng,Li Ying,Yang Chuanyu,Ma Xinyue,Li Hongxia,Sun Chunyan
Based on a Pb 2+ -specific 8–17 DNAzyme-induced catalytic hairpin assembly (CHA), a simple signal-on fluorescence strategy for lead ion detection was established. 8–17 DNAzyme was used as the recognition element of Pb 2+ , which catalyzed the cleavage of the RNA base embedded in the DNA substrate strand, while releasing part of the substrate strand (S’) as CHA initiator. And two hairpin probes (H1 and H2-FQ) were designed according to the sequence of S’ for CHA, in which H2-FQ was labeled with the fluorophore FAM and quencher BHQ-1 as fluorescent “molecular switch” based on fluorescence resonance energy transfer (FRET). In the presence of Pb 2+ , the CHA reaction was triggered to form a large number of H1-H2 complexes, enabling enzyme-free isothermal amplification and a signal-on fluorescence strategy. In the concentration range of 0.5–1000 nM, the fluorescence signal increases with the increase of Pb 2+ concentration. The quantitative detection limit of Pb 2+ by this method is 0.5 nM, which has better detection performance compared with the FQ-labeled 8–17 DNAzyme method. The established biosensor exhibits good specificity and can be effectively used for the detection of Pb 2+ in real samples of river water and grass carp. Through ingenious nucleic acid sequence design, DNAzyme and CHA reactions are integrated to realize the enzyme-free isothermal amplifications and sensitive detection of Pb 2+ , which holds potential versatility in food supervision and environmental monitoring. Graphical abstract
危险品化学品经营许可证（带存储）