AVS 50th International Symposium
    Homeland Security Topical Conference Thursday Sessions
       Session HS-ThM

Paper HS-ThM1
Direct Electrical Detection of Specific Protein Binding at Surfaces

Thursday, November 6, 2003, 8:20 am, Room 309

Session: Detection of Biological Agents and Self-Cleaning of Contaminated Surfaces
Presenter: T.L. Lasseter, University of Wisconsin, Madison
Authors: T.L. Lasseter, University of Wisconsin, Madison
W. Cai, University of Wisconsin, Madison
W. Yang, University of Wisconsin, Madison
R.J. Hamers, University of Wisconsin, Madison
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Most biological analyses ultimately rely on optical methods of detection. Here, we show that the binding of proteins to surfaces can be detected electrically in a completely label-free manner using electrochemical impedance spectroscopy. Experiments have been conducted on several different substrates including gold, glassy carbon, and silicon. In each case, we covalently linked biotin to the surface, and then investigated the changes in electrical impedance when the surface was exposed to avidin over the frequency range from 5 mHz to 1 MHz. The changes in impedance are most apparent at low frequencies, < 1 Hz. By using fluorescently-labeled avidin, we also correlated the magnitude of the observed electrical changes with the intensity of the observed fluorescence from the surface. Measurements of the impedance changes as a function of avidin concentration show that the detection limit from these electrical measurements is comparable to or even better than the detection limit observed from fluorescence spectroscopy. Finally, circuit modeling of the interface is being use to relate the electrical changes observed to the physical structure of the interface.