Graphene- and aptamer-based electrochemical biosensor

This study investigated the effectiveness of a graphene- and aptamer-based field-effect-transistor-like (FET-like) sensor in detecting lead and potassium ions. The sensor consists of a graphene-covered Si/SiO2 wafer with thrombin binding aptamer (TBA) attached to the graphene layer and terminated by a methylene blue (MB) molecule. K+ and Pb2+ both bind to TBA and cause a conformational change, which results in MB moving closer to the graphene surface and donating an electron. Thus, the abundance of K+ and Pb2+ can be determined by monitoring the current across the source and drain channel. Device transfer curves were obtained with ambipolar field effect observed. Current readings were taken for K+ concentrations of 100 mu M to 50 mM and Pb2+ concentrations of 10 mu M to 10 mM. As expected, I-d decreased as ion concentration increased. In addition, there was a negative shift in V-Dirac in response to increased ion concentration.