Advancements in biological and chemical warfare has allowed for the creation of novel toxins necessitating a universal,
real-time sensor. We have used a function-based biosensor employing impedance spectroscopy using a low current
density AC signal over a range of frequencies (62.5 Hz-64 kHz) to measure the electrical impedance of a confluent
epithelial cell monolayer at 120 sec intervals. Madin Darby canine kidney (MDCK) epithelial cells were grown to
confluence on thin film interdigitated gold electrodes. A stable impedance measurement of 2200 Ω was found after 24
hrs of growth. After exposure to cytotoxins anthrax lethal toxin and etoposide, the impedance decreased in a linear
fashion resulting in a 50% drop in impedance over 50hrs showing significant difference from the control sample (~20%
decrease). Immunofluorescent imaging showed that apoptosis was induced through the addition of toxins. Similarities of
the impedance signal shows that the mechanism of cellular death was the same between ALT and etoposide. A revised
equivalent circuit model was employed in order to quantify morphological changes in the cell monolayer such as tight
junction integrity and cell surface area coverage. This model showed a faster response to cytotoxin (2 hrs) compared to
raw measurements (20 hrs). We demonstrate that herein that impedance spectroscopy of epithelial monolayers serves as
a real-time non-destructive sensor for unknown pathogens.
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