A reagentless aptasensor based on intrinsic aptamer redox activity for the detection of tetracycline in water

•A label-free electrochemical aptasensor has been designed for the determination of tetracycline (TET) in water.•The 5′The anti-TET aptamer displayed an unexpected electroactivity.•Cyclic voltammetry was used to detect TET at concentrations ranging from 0.05 μg/L to 20 μg/L, with a detection limit of 0.035 μg/L.•The aptasensor was successfully used for the detection of TET in natural waters, with recovery rates close to 100%.