Dual dye-labeled G-quadruplex aptasensor for detection of thallium(I) using ratiometric fluorescence resonance energy transfer

Abstract

A fluorescent probe was developed for ratiometric detection of thallium ions in mineral water samples by modifying a G-rich aptamer (PS2.M - 7) with a fluorescence donor (Cyanine-3, Cy₃) and a quencher (Cyanine-5, Cy₅). The probe had a random coil structure that changed into a G-quadruplex structure upon binding with Tl⁺. This change in structure decreased the distance between the donor and acceptor moieties, which resulted in fluorescence resonance energy transfer between Cy₃ and Cy₅. Under optimized conditions, the limit of detection and linear concentration range for Tl⁺ were 30.1 μM (3σ) and 10 μM-10 mM (R² = 0.9981), respectively. This simple and cost-effective fluorescence sensor provided satisfactory results for detection of thallium ions in spiked mineral water samples.

Keywords: Aptamer; Fluorescence resonance energy transfer; Fluorescence sensor; G-quadruplex; Thallium detection.