Control of antibody-antigen binding or dissociation by electric field

The development of a biosensor with adequate sensitivity generally requires a biospecific interaction with high binding affinity. The affinity constants for most antibody-antigen interactions are determined largely by the dissociation constants, k(d), with little variation observed in rates of association. Additionally, surface immobilization typically results in a reduced k(d). In this case, the sensor binds analyte kinetically irreversibly preventing response to changes in analyte concentration or reuse. Regeneration of the sensor surface is difficult, at best. On the other hand, a higher dissociation rate which would lend itself to a linear and reusable sensor, results in lower affinity and poor sensitivity. Consequently, most biosensors are disposable devices and quantitation is obtained using multiple single-use sensors. In this work, a new reusable biosensor platform which provides simultaneous fluorescence detection and electrochemical control of biospecific binding has been developed. Biotin was covalently attached to a transparent indium tin oxide (ITO) electrode, which also served as an integral part of a total internal reflection fluorescence (TIRF) flow cell. TIRF was used to monitor biospecific interactions while electrochemical polarization was employed to control the interactions. Two possible mechanisms of the electric field effect involving interactions with induced and permanent dipoles of proteins will be discussed.