Organic field-effect transistor-based biosensors functionalized with protein receptors

An organic field-effect transistor with integrated proteins (Bio-FET) for sensing of sulfate ions is presented. A sulfate receptor was engineered to contain a thiol group for surface-anchoring without affecting its binding activity. The modified receptor was covalently coupled to a maleimide-functionalized polystyrene layer, and integrated as gate dielectric in a dual-gate transducer. The binding of sulfate ions in dry conditions was detected by a shift in the threshold voltage. Combined with surface density measurements by atomic force microscopy, an effective charge of -1.7q per protein was found, as expected from the Bio-FET operation model. (C) 2010 American Institute of Physics. [doi:10.1063/1.3518681]