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 Pb(2+) 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 Pb(2+) 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 μM to 50 mM and Pb(2+) concentrations of 10 μM 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.