Figure 3.

Presence of non-adsorbed streptavidin protein modulates the measured impedance. (a) Various concentrations of streptavidin were injected onto our sensor surface sequentially: (1) water, (2) 250 ng/ml streptavidin, (3) 25 ug/ml streptavidin, (4) 25 mg/ml streptavidin. Between every step that protein was added we dried out the measurement well. As the concentration of protein in the solution decreases, the measured impedance increases getting closer and closer to the baseline value. (b) Impedance response of polystyrene beads injected onto sensor resulting in increase in impedance. (c) Impedance change plotted with error bars over three measurements per point.