Recyclable Target Metal-Enhanced Fluorometric Naked Eye Aptasensor for the Detection of Pb 2+ and Ag + Ions Based on the Structural Change of CaSnO 3 @PDANS-Constrained GC-Rich ssDNA

• Published in: ACS omega 2021-11, Vol.6 (45), p.30580-30597
• Main Authors: Amalraj, Arunjegan, Pavadai, Rajaji, Perumal, Panneerselvam
• Format: Article
• Language: English
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.1c04319

Reliable, label-free, and ultraselective detection of Pb and Ag ions is of paramount importance for toxicology assessment, human health, and environmental protection. Herein, we present a novel recyclable fluorometric aptasensor based on the Pb and Ag -induced structural change of the GC-rich ssDNA (guanine cytosine-rich single-strand DNA) and the differences in the fluorescence emission of acridine orange (AO) from random coil to highly stable G-quadruplex for the detection of Pb and Ag ions. More interestingly, the construction and principle of the aptasensor explore that the GC-rich ssDNA and AO can be strongly adsorbed on the CaSnO @PDANS surface through the π-π stacking, hydrogen-bonding, and metal coordination interactions, which exhibit high fluorescence quenching and robust holding of the GC-rich ssDNA. However, in the presence of Pb , the specific G-rich ssDNA segment could form a stable G-quadruplex via G4-Pb coordination and capture of AO from the CaSnO @PDANS surface resulting in fluorescence recovery (70% enhancement). The subsequent addition of Ag ion induces coupled cytosine base pairs in another segment of ssDNA to get folded into a duplex structure together with the G-quadruplex, which highly stabilizes the G-quadruplex resulting in the maximum recovery of AO emission (99% enhancement). When the Cys@Fe O Nps are added to the above solution, the sensing probe was restored by complexation between the Cys in the Cys@Fe O Nps and target metal ions, resulting in the fabrication of a highly sensitive recyclable Pb and Ag assay with detection limits of 0.4 and 0.1 nM, respectively. Remarkably, the Cys@Fe O Nps can also be reused after washing with EDTA. The utility of the proposed approach has great potential for detecting the Pb and Ag ions in environmental samples with interfering contaminants.