Impact of Molecular Surface Charge on Electrical Impedance Spectroscopy Biosensing
Poster Mar 08, 2015
Y. Ram, T. Yoetz-Kopelman, A. Freeman and Y. Shacham-Diamand
Electrical Impedance Spectroscopy (EIS) is a powerful tool for detection and characterization for biorecognition events at the surface. It enables to perform measurements with high sensitivity without damaging biologic samples.
Employing a redox couple as probe in impedance measurements is beneficial, since it is highly sensitive to changes in the surface charge that can either increase or decrease the resistance to electrochemical charge transfer.
The goal of this work is to use EIS for biodetection of proteins, and to gain physical understanding of the detection mechanism.
The Avidin-Biotin interaction was used for the binding of biotinylated HRP to the surface of the electrode without the need to use SAM, to modify the proteins or to add a blocking layer.
Since [Fe(CN)6]3−/[Fe(CN)6]4- were used as the redox couple, it was found advantageous to use an amide-modified form of Avidin which is less positive than the original molecule. Thus, the change in resistance is much higher.
This work shows that the charge of the analyte is much more influential than its size when using EIS in comparison to two other common techniques - Cyclic Voltammetry and ELISA. In addition, detection of biotinylated HRP was achieved for concentrations in the nanomolar range.