A multifunctional fluorescent aptamer probe for highly sensitive and selective detection of cadmium(II)

Abstract

We report a highly sensitive and selective strategy for Cd(II) assay using a singly labeled multifunctional probe consisting of a Cd(II)-specific aptamer (CAP), which acted as a recognition element for Cd(II) and a signal reporter. The presence of Cd(II) can induce the conformational switching of the CAP, accompanied by a change in fluorescence intensity. Thereby, a fluorescence strategy for Cd(II) assay was established. The proposed method has a detection limit of 2.15 nM, which is much lower than the detection limits reported in related literature. This strategy involves only an aptamer probe, and the use of such a G-based quencher avoids the dual labeling of the CAP with fluorophore/quencher units. It is obviously more convenient and economical than the other aptamer-based biosensors for Cd(II) detection. The mechanism by which Cd(II) induces the CAP to change from a random coil sequence to a stem-loop structure was studied in a series of control experiments. This strategy would be helpful in the design of a sensitive analytical platform for various target assays in environmental and biomedical fields. Graphical Abstract The presence of Cd leads to the conformational change of CAP from a random coil sequence to a stem-loop structure, resulting in a quenching in the fluorescence.

Methionine-Capped Gold Nanoclusters as a Fluorescence-Enhanced Probe for Cadmium(II) Sensing

“…As displayed in Figure 5 A, the fluorescence intensity increased significantly with the increasing solution pH, and reached its maximum when pH reached 8.0. A possible explanation for this is that the pH influences the Cd 2+ ion speciation in solution [ 37 ]. Therefore, pH 8.0 was selected as the optimum pH value for Cd 2+ ion detection.…”

Bio-Recognition in Spectroscopy-Based Biosensors for *Heavy Metals-Water and Waterborne Contamination Analysis

“…In another arrangement, Y.F. Zhu et al proposed a singly-labeled bifunctional probe consisting of a Cd 2+ -specific aptamer (CAP), capable to act as the recognition element for Cd 2+ and the signal reporter [66]. The Cd 2+ presence induces the switching of the CAP coil conformation to a stem-loop structure, which brings the four guanosine bases at the 5′ end close to 6-Fam at the 3′ end, resulting in fluorescence quenching.…”

Fluorescent Sensors for the Detection of Heavy Metal Ions in Aqueous Media

“…The intensity (or lifetime) of that emission varies with the concentration of the target analyte [31]. So far, several materials, such as porphyrins [32], metal-organic frameworks [33], DNAzymes [34], fluorescent aptamers [35], quantum dots [36], or organic dyes [37] have been developed for the monitoring of heavy metal ions in water. This review is focused on the recent advances in sensors that employ the last three kinds of materials: the first section is devoted to the different techniques based on fluorescent aptamers, the second one is dedicated to the sensors fabricated with quantum dots and, finally, the third one analyzes the devices developed using organic dyes.…”