Detection of Small Molecule Analytes with Biosensors based on Electrochemical Impedance Spectroscopy

Author

Madhavi L. Pali, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2019

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Suni, Ian

Abstract

Several different approaches were studied to improve and understand the sensitivity and detection limit that could be obtained for biosensors that utilize electrochemical impedance spectroscopy (EIS) for signal transduction. The first project involves the detection of fish hormones by applying Electrochemical impedance spectroscopy (EIS) & Quartz crystal microbalance (QCM) techniques. Detection of three fish hormones, cortisol, insulin-like growth factor 1 (IGF-1), and vitellogenin is studied by both electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM), and the EIS (QCM) detection limits are 7.9 (0.50) μM, 3.0 (2.4) nM, and 43 (13) pM, respectively, in PBS buffer. Thus, the two detection methods, EIS and QCM, have similar sensitivity, but QCM is four times more in magnitude while it comes to sensitiveness consideration, which is consistent with the published literature. The molecular weights of cortisol, IGF-1, and vitellogenin are 362.5 Da, 7.3 kDa, and 440.5 kDa, respectively. For both EIS and QCM, the sensitivity and detection limit improve dramatically with increasing molecular weight, reflecting the larger change in polymer-protein film thickness at the Au electrode upon recognition and binding of larger analytes. Potential applications to the understanding of fish physiology are discussed, including hormone detection in fish blood plasma, and ambient water.