Novel aptamer fluorescence assays for malachite green and leucomalachite green detection

Simple fluorescence aptasensors were established for malachite green (MG) and leucomalachite green (LMG) detection using G-quadruplex dyes thioflavin T (ThT) and thiazole orange (TO), respectively. ThT and TO, initially non-fluorescent in aqueous solution, exhibited fluorescence upon binding to target-specific aptamers, resulting in the stabilization of G-quadruplex structures. The specific binding between G-quadruplex and MG could induce conformational changes, which caused a pronounced quenching of fluorescence emitted by the intercalator, providing a possibility for detection. The developed assays demonstrated a good linear relationship in the range of 0–1000 μg L -1 for MG and 0–250 μg L -1 for LMG, with low limits of detection of 5.4 × 10 -3 μg L -1 and 0.1 μg L -1 respectively. More importantly, satisfactory detection results in water and fish samples were obtained. Noteworthy was that the uncomplicated fluorescent aptasensors operated effectively without the need for any modifications. The experimental process was facile and realized in homogeneous solution, which exhibited quick responsiveness after simple mixing.