Diclofenac aptasensor based on graphene field-effect transistor

Biosensors are analytical tools whose performance is highly influenced by the transducing method and the construction protocol. Graphene field-effect transistors (GFETs) are recognized as sensitive sensors owing to their strong response to changes in surface charge, but their use is limited by complex fabrication and integration processes. In this work, we employ a straightforward method to modify commercially available GFET surfaces via diazonium salt reduction, yielding reproducible and robust interfaces. Using a protective-deprotective strategy to form controlled nanostructured monolayers, a GFET aptamer-based sensor was developed for the detection of diclofenac (DCF). For that purpose, an azide-modified aptamer sensitive to DCF was immobilized on the surface of the functionalized graphene by click chemistry, an orthogonal and biocompatible covalent immobilization strategy. The sensor had a linearity range from 5 to 100 nM, reaching a satisfactory limit of detection of 3.1 nM, comparable to the concentrations of the analyte found in the environment. Moreover, the sensor has good selectivity, stability, repeatability, and performance in river water. This strategy marks the first attempt to develop an aptamer-based GFET sensor for DCF detection.