A Sensitive and Label‐Free Ratiometric Fluorescent Aptasensor for Rapid Quinine Detection in Environmental and Food Samples

Abstract Quinine (QN), a widely used alkaloid in food and pharmaceuticals, can pose health risks at elevated levels, necessitating the development of sensitive and rapid detection methods. Here, we report a label‐free, ratiometric fluorescent aptasensor for the sensitive and selective detection of QN. The sensing platform integrates a quinine‐specific DNA aptamer (Apt QN ) with crystal violet (CV), a triphenylmethane (TPM) dye exhibiting near‐infrared (NIR) emission, and fluorescein isothiocyanate (FITC) as an internal reference. Upon QN binding, CV is competitively displaced from the aptamer complex, resulting in fluorescence quenching, while FITC emission remains stable, facilitating self‐calibrated quantification. The aptasensor exhibits high sensitivity, rapid response within one minute and robust analytical performance in complex samples, such as lake water and soft drinks. This cost‐effective and efficient sensing strategy provides a reliable approach for QN monitoring in food safety and environmental applications.