Impedimetric or Ion-Sensitive Field-Effect Transistor (ISFET) Aptasensors Based on the Self-Assembly of An Nanoparticle-Functionalized Supramolecular Aptamer Nanostructures

Two electrical methods (Faradaic impedance spectroscopy and ion-sensitive field-effect transistor (ISFET)) are applied to sense aptamer-substrate complexes. The methods utilize anticocaine aptamere fragments that self-assemble in the presence of cocaine, to a supramolecular aptamer fragments/cocame complex on the electrode surface or ISFET gate. One of the aptamer fragments is assembled on a Au electrode or the ISFET gate. The second thiolated aptamer fragment is used to modify Au NPs that are used as amplifying labels for the two detection schemes. The impedimetric and ISFET methods enabled the analysis of cocaine with detection limits of 1 x 10(-5) M and 1 x 10(-6) M. respectively.