Virus-poly(3,4-ethylenedioxythiophene) composite films for impedance-based biosensing

Composite films composed of poly(3,4-ethylenedioxythiophene), PEDOT, and the filamentous virus M13-K07 were prepared by electrooxidation of 3,4-ethylenedioxythiophene (EDOT) in aqueous solutions containing 8 nM of the virus at planar gold electrodes. These films were characterized using atomic force microscopy and scanning electron microscopy. The electrochemical impedance of virus-PEDOT films increases upon exposure to an antibody (p-Ab) that selectively binds to the M13 coat peptide. Exposure to p-Ab causes a shift in both real (Z RE) and imaginary (Z IM) impedance components across a broad range of frequencies from 50 Hz to 10 kHz. Within a narrower frequency range from 250 Hz to 5 kHz, the increase of the total impedance (Z total) with p-Ab concentration conforms to a Langmuir adsorption isotherm over the concentration range from from 6 to 66 nM, yielding a value for K d = 16.9 nM at 1000 Hz.