%0 Journal Article %A Cardinell, Brittney A. %A Spano, Mark L. %A La Belle, Jeffrey %D 2019 %I Begell House %K cortisol, stress, point-of-care technology, electrochemistry, electrochemical impedance spectroscopy %N 3 %P 207-215 %R 10.1615/CritRevBiomedEng.2019026109 %T Toward a Label-Free Electrochemical Impedance Immunosensor Design for Quantifying Cortisol in Tears %U https://www.dl.begellhouse.com/journals/4b27cbfc562e21b8,3cc2283a1f3a0874,7fa3645f078e02e1.html %V 47 %X Cortisol is a viable biomarker for monitoring physiological, occupational, and emotional stress and is normally present in tear fluid at approximately 40 nM, or higher as a result of stress. We present characterization and quantification of cortisol via several electrochemical methods versus the standard enzyme-linked immunosorbent assay, commonly known as ELISA. We also present a prototyped design of a disposable test strip and handheld sensor based on label-free electrochemical impedance spectroscopy to quantify cortisol levels in tear fluid within approximately 90 seconds. Electrochemical characterization of the cortisol molecule was conducted using cyclic voltammetry, amperometric i-t, and square wave voltammetry. Lower limits of detection for these techniques were not sufficient to quantify cortisol and phycological tear ranges: 0.1 M, 0.23 M, and 193 M for cyclic voltammetry, amperometric i-t, and square wave voltammetry, respectively. However, electrochemical impedance spectroscopy (EIS) was to be the best mode of cortisol quantification and comparison to ELISA technique (detection range of ~ 138 pM – 552 nM). The initial EIS biosensor obtained a lower limit of detection of 59.76 nM with an approximate 10% relative standard deviation. The cortisol assay and tear collection prototype presented here offer a highly reproducible and ultra-low level of detection with a label-free and rapid response. %8 2019-05-17