Dynamic control of protein-protein interactions.

The capability to selectively and reversibly control protein-protein interactions in antibody-doped polypyrrole (PPy) was accomplished by changing the voltage applied to the polymer. Polypyrrole was doped with sulfate polyanions and monoclonal anti-human fibronectin antibodies (alphaFN). The ability to toggle the binding and dissociation of fibronectin (FN) to alphaFN-doped polypyrrole was demonstrated. Staircase potential electrochemical impedance spectroscopy (SPEIS) was performed to characterize the impedance and charge transfer characteristics of the alphaFN-doped PPy as a function of applied voltage, frequency, and FN concentration. Impedance measurements indicated oxidation of alphaFN-doped PPy promoted selective binding of FN to alphaFN antibodies and reduction of the polymer films facilitated FN dissociation. Moreover, SPEIS measurements suggested that the apparent reversibility of antigen binding to antibody-doped PPy is not due to the suppression of hydrophobic binding forces between antibody and antigen. Instead, our data indicate that reversible antigen binding to antibody-doped PPy can be attributed to the minimization of charge in the polymer films during oxidation and reduction. Furthermore, alphaFN-doped PPy was utilized to collect real-time, dynamic measurements of varying FN concentrations in solution by repeatedly binding and releasing FN. Our data demonstrate that antibody-doped PPy represents an electrically controllable sensing platform which can be exploited to collect rapid, repeated measurements of protein concentrations with molecular specificity.