A Sensitive and Label-Free Pb(II) Fluorescence Sensor Based on a DNAzyme Controlled G-Quadruplex/Thioflavin T Conformation

Abstract

Pb(II) can cause serious damaging effects to human health, and thus, the study of Pb2+ detection methods to sensitively and selectively monitor Pb(II) pollution has significant importance. In this work, we have developed a label-free fluorescence sensing strategy based on a Pb(II) DNAzyme cleavage and the ThT/G-quadruplex complex. In the presence of Pb(II), a G-rich tail was cut and released from the substrate strand, which then would form a G-quadruplex structure by combination with ThT dye. The fluorescence signal increase was then measured for sensitive Pb(II) quantification with a limit of detection of 0.06 nM. Our sensor also demonstrated high selectivity against six different metal ions, which is very important for the analysis of complex samples.

Fluorescence and Naked-Eye Detection of Pb²⁺in Drinking Water Using a Low-Cost Ionophore Based Sensing Scheme

“…Comparisons and a brief overview of literature shows that laboratory instrumental techniques nmol L −1 (200 ppt), using a polyguanine (G(33))/terbium ions (Tb(3+)) conjugate [23]. The best fluorescence detection we found to date are another DNAzyme technique showing a detection limit of 0.06 nmol L −1 (12 ppt) [24]. Additionally, there are convenient commercial colorimetric test sticks for Pb 2+ detection, for example MQuant TM from Merck.…”

Fluorescence and Naked-Eye Detection of Pb2+ in Drinking Water Using a Low-Cost Ionophore Based Sensing Scheme

“…One among the top-notch fluorescence techniques for Pb 2+ ions demonstrated a detection limit of 1 nmol L −1 (200 ppt), using a polyguanine (G(33))/terbium ions (Tb(3+)) conjugate [23]. The best fluorescence detection we found to date are another DNAzyme technique showing a detection limit of 0.06 nmol L −1 (12 ppt) [24]. Additionally, there are convenient commercial colorimetric test sticks for Pb 2+ detection, for example MQuant TM from Merck.…”

Advanced Selection Methodologies for DNAzymes in Sensing and Healthcare Applications

“…In addition, because there is no risk of binding-site modification, they tend to be more popular than labeled aptasensors. This approach has been applied by many groups to develop an array of label-free biosensors against a vast range of target molecules ( Table 2) [66][67][68][69][70]. These DNAzyme-based biosensors are of great interest for real-time detection of heavy metals in water samples.…”

“…More recently, different fluorescence modules have been developed for applications in real-time detection. The bichromophore approach is commonly used for fluorescence-based DNAzymes [68,70], and amplification methodologies such as PCR and RCA have also been investigated to enhance the detection limit of fluorescence-based aptasensors. In this respect, immuno-PCR (IPCR) has been proposed as a promising technique for the future [134].…”

“…The fluorescence signals generated can be monitored using different systems such as anisotropy, bichromophores, fluorescence resonance energy transfer (FRET), and antisense con-formational triggers [68,70]. The detection sensitivity of DNAzyme-based point-of-care devices can be enhanced by incorporating advanced techniques such as real-time PCR and rolling circle amplification (RCA) (Box 4).…”