Lead(II)-Induced Allosteric G-Quadruplex DNAzyme as a Colorimetric and Chemiluminescence Sensor for Highly Sensitive and Selective Pb2+ Detection

摘要

The lead ion (Pb2+) has been proven to induce anconformational change of K+-stabilized G-quadruplexnDNAzyme and inhibit the peroxidase-like activity [Li,nT.; Wang, E.; Dong, S. J. Am. Chem. Soc. 2009, 131,n15082-15083]. This provides a rationale for utilizingnPb2+-induced allosteric G-quadruplex DNAzyme tonprobe aqueous Pb2+. Here, we choose a commonnG-quadruplex DNAzyme named PS2.M to develop annovel Pb2+ sensor with two detection means: colorimetrynand chemiluminescence (CL). In the presence ofnK+, PS2.M (with hemin as a cofactor) exhibits ansuperior DNAzyme activity and effectively catalyzes thenH2O2-mediated oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-n6-sulfonic acid) diammonium salt (ABTS)nor luminol, which results in a color change or generatesnCL emission. Upon the addition of Pb2+, K+-stabilizednPS2.M is induced to convert to the Pb2+-stabilizednstructure with higher stability but lower DNAzymenactivity, which is reflected by an obvious increase innDNA melting temperature but a sharp decrease innreadout signal. This allows us to utilize PS2.M fornquantitative analysis of aqueous Pb2+ using thenABTS-H2O2 colorimetric system and luminol-H2O2nCL system. In each case, the readout signal is linearlyndependent on the logarithm of Pb2+ concentrationnwithin a certain range. Nevertheless, two sensingnsystems provide different sensitivity for Pb2+ analysis.nWith colorimetry, Pb2+ can be detected at a level of 32nnM (∼7 ppb), whereas the detection limit of Pb2+ is 1nnM (0.2 ppb) when utilizing the CL method. In additionnto high sensitivity, the above sensing systemsnexhibit good selectivity for Pb2+ over other metal ions.nThese results demonstrate the facility and effectivitynof our introduced DNAzyme-based sensor for quantitativenPb2+ analysis.