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.

Colorimetric assay of lead using unmodified gold nanorods

“…Even with sensitivity and accuracy, there also share some disadvantages, such as timeconsuming, expensive, and/or require sophisticated equipment, etc. To overcome these limitation and drawbacks, a variety of sensors have been developed to rapidly detect lead with high selectivity and sensitivity [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Among them, colorimetric sensors offer a promising approach for facile tracking of metal ions in biological, toxicological, and environmental samples.…”

“…The detection range of the sensor could be tuned from 3 nM to 1 μM [19][20][21][22][23][24][25]. Dong and co-workers reported a DNAzymebased colorimetric sensor for Pb 2+ ; the detection limit was 32 nM [26]. In this paper, we aim to develop an ultrasensitive, environmentally friendly, yet simple method for colorimetric detection of Pb 2+ ion.…”

Potential uses of G-quadruplex-forming aptamers

“…The issue of the high sensitivity of the TBA sequence to various cations is raised in research focused on the detection of K + Cai et al 2010), Pb 2+ and Hg 2+ (Liu et al 2009;Li et al 2010) using various physical methods. TBA sequences were also incorporated in nanopores formed by α-hemolysin (α HL) in bilayer lipid membrane; the addition of cations, especially K + , resulted in the folding of TBA into quadruplexes and reduced the current flowing through the nanopore (Shim et al 2009).…”

Characterization of Metal Ion-Nucleic Acid Interactions in Solution

“…The latter have been shown to discriminate against Mg 2+ , while selecting for Ca 2+ [89][90][91], Cu 2+ [92][93][94], Co 2+ [95], Zn 2+ [96], Mn 2+ [94], Pb 2+ [97], Ni 2+ [98] or a small subgroup of transition metal ions [99]. By the same means extraordinarily selective DNA biosensors for various metal ions have been engineered [100,101] (see also Chapter 8).…”