Abstract

Non-invasive and high sensitive electrochemical impedance spectroscopy (EIS) has been used for qualitative characterization of stepwise surface preparation process for constructing an immunosensor, starting from plain silicon substrate, 3-aminopropyltriethoxysilane (APTES) silanization, glutaraldehyde functionalization and analytes (rat immunoglobulin G immobilization, followed by protein G-coated gold nanoparticles), using both the horizontal direction (2 terminal) and vertical direction (3 terminal) characterization setup. The investigation demonstrated that 2-terminal setup is able to review the quality of antibody and antigen molecules bonding and distinguish the effects from the underlayers on the immuosensors; while 3-terminal setup is able to correlate the thickness and dielectric constant of each layers. It correlated well to the incubation time of preparing different sensors as well. The two different EIS measurement setups are able to serve different needs for immunosensor characterization and EIS measurement shows higher sensitivities compared with UV-Vis absorption measurement.