title: Lead(II)-induced allosteric G-quadruplex DNAzyme as a colorimetric and chemiluminescence sensor for highly sensitive and selective Pb2+ detection.
abstract: The lead ion (Pb(2+)) has been proven to induce a conformational change of K(+)-stabilized G-quadruplex DNAzyme and inhibit the peroxidase-like activity [Li, T.; Wang, E.; Dong, S. J. Am. Chem. Soc. 2009, 131, 15082-15083]. This provides a rationale for utilizing Pb(2+)-induced allosteric G-quadruplex DNAzyme to probe aqueous Pb(2+). Here, we choose a common G-quadruplex DNAzyme named PS2.M to develop a novel Pb(2+) sensor with two detection means: colorimetry and chemiluminescence (CL). In the presence of K(+), PS2.M (with hemin as a cofactor) exhibits a superior DNAzyme activity and effectively catalyzes the H(2)O(2)-mediated oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) or luminol, which results in a color change or generates CL emission. Upon the addition of Pb(2+), K(+)-stabilized PS2.M is induced to convert to the Pb(2+)-stabilized structure with higher stability but lower DNAzyme activity, which is reflected by an obvious increase in DNA melting temperature but a sharp decrease in readout signal. This allows us to utilize PS2.M for quantitative analysis of aqueous Pb(2+) using the ABTS-H(2)O(2) colorimetric system and luminol-H(2)O(2) CL system. In each case, the readout signal is linearly dependent on the logarithm of Pb(2+) concentration within a certain range. Nevertheless, two sensing systems provide different sensitivity for Pb(2+) analysis. With colorimetry, Pb(2+) can be detected at a level of 32 nM (approximately 7 ppb), whereas the detection limit of Pb(2+) is 1 nM (0.2 ppb) when utilizing the CL method. In addition to high sensitivity, the above sensing systems exhibit good selectivity for Pb(2+) over other metal ions. These results demonstrate the facility and effectivity of our introduced DNAzyme-based sensor for quantitative Pb(2+) analysis.
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022, People's Republic of China.
authors.forename: Tao
authors.initials: T
authors.lastname: Li
authors.forename: Erkang
authors.initials: E
authors.lastname: Wang
authors.forename: Shaojun
authors.initials: S
authors.lastname: Dong
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects; D000818:Animals; D001483:Base Sequence; D052160:Benzothiazoles / Q000378:metabolism; D015374:Biosensing Techniques / Q000379:methods*; D002417:Cattle; D002942:Circular Dichroism; D003124:Colorimetry; D021881:DNA, Catalytic / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054856:G-Quadruplexes / Q000187:drug effects*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D007854:Lead / Q000032:analysis* / Q000494:pharmacology*; D008163:Luminescent Measurements; D008165:Luminol / Q000378:metabolism; D009841:Oligonucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013451:Sulfonic Acids / Q000378:metabolism; D014867:Water / Q000737:chemistry
chemical_list: D052160:Benzothiazoles; D021881:DNA, Catalytic; D009841:Oligonucleotides; D013451:Sulfonic Acids; D014867:Water; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D007854:Lead; D008165:Luminol; D006861:Hydrogen Peroxide