Femtomolar Level-Specific Detection of Lead Ions in Aqueous Environments, Using Aptamer-Derivatized Graphene Field-Effect Transistors

The detection of lead ion (Pb2+) contamination in aqueous media is relevant for preventing endemic health issues as well as damage to cognitive and physical health. Existing home kit tests are unable to achieve clinically relevant sensitivity and specificity. Here, a label-free graphene field-effect transistor sensor for detecting Pb2+ at the femtomolar (fM) level, discriminating between confounding ions, is reported. The sensing principle is based on electrically monitoring Pb2+-binding-mediated conformational changes of a specific aptamer tethered to graphene, modeled through the Hills-Langmuir mechanism. A record sensitivity-through a limit of detection of similar to 61 fM, for Pb2+ was demonstrated. For model verification, specific discrimination of Pb2+ from other ions at the 1 picomolar (pM) level was shown. The reported work provides motivation for development of portable, label-free, point-of-care devices with both high specificity and sensitivity.