An Extended-Gate Ion-Sensitive Field-Effect Transistor Based on Aptamer Capture for Ultrasensitive Detection of Tetracycline in River Water Samples

The widespread use of tetracycline (TC) has resulted in its frequent occurrence in aquatic environments because of incomplete metabolism and continuous release, raising increasing concerns regarding water quality and environmental safety. Reliable determination of trace TC in real water samples remains challenging owing to its low concentration and the complex sample matrix. In this work, an aptamer-functionalized extended-gate ion-sensitive field-effect transistor (EG-ISFET) was developed for sensitive TC detection. The sensing interface was constructed by immobilizing a TC-specific aptamer on a Ta2O5 extended gate. Upon target recognition, aptamer folding redistributes the interfacial charge, thereby modulating the surface potential of the extended gate and producing a measurable field-effect response. The proposed sensor exhibits a broad linear detection range from 1 pM to 1 μM with a detection limit of 0.33 pM. To facilitate practical applications, a compact plug-and-play point-of-care testing (POCT) platform integrating the EG-ISFET sensor was further developed for rapid on-site analysis. The portable system demonstrated satisfactory accuracy and reliability for the determination of TC in river water samples, highlighting its potential for environmental monitoring and point-of-use water quality assessment.