Aptamer-Engineered Extended-Gate Field Effect Transistor Device for Point-of-Care Therapeutic Drug Monitoring Mengyang Zhang, Junqing He, Youbin Zheng, Guoyue Shi and Min Zhang Abstract Herein, we report a portable point-of-care tesing (POCT) device based on aptamer-engineered extended-gate field effect transistor (EG-FET) for therapeutic drug monitoring of methotrexate. This method owing highly sensitivity, efficiency and convenience contributes to realizing clinic detection for blood drug.