Impedance Spectroscopy to Measure Placental Barrier Integrity

Abstract

Various placenta models have been developed, including in-vivo, ex-vivo, and in-vitro approaches, aiming to provide a better understanding of the placental barrier and its interactions with medicinal drugs during pregnancy. The in-vitro model and specifically the placenta-on-a-chip models have shown significant promises as an alternative to conventional in-vitro, in-vivo, and ex-vivo models for investigating the fetal exposure to drugs administered to pregnant mothers. The use of non-invasive techniques allows for continuous monitoring of barrier integrity without damaging the cells. One technique allowing such monitoring is called bioimpedance spectroscopy to measure the transepithelial/transendothelial electrical resistance (TEER) and the electrical capacitance of cell membrane. The aim of this thesis is to (i) Design and optimize a low cost, effective and reproducible impedance measuring device to assess the placenta barrier permeability changes; (ii) Measure and track electrical properties of a monolayer of epithelial cells to validate the setup; (iii) Capture and process syncytialisation data from TEER to correlate with the cell fusion index obtained from immunofluorescence imaging and (iv) Propose a Lab-on-a-Chip (LOC) design to mimic a physiological placental barrier in-vitro. We show that the developed impedance spectroscopy system is suitable to measure and track barrier permeability. The measurements confirmed the formation of a confluent monolayer at Day 4. The electrical resistance tripled for treated samples showing the formation of a confluent layer. This resistance remained constant for treated samples reflecting the intact cell barrier and retention of the barrier's integrity over the next 3 days. The resistance of the untreated samples remained in an increasing linear trend due to its lack of fusion and multiple layer formation. The measurements show that, at Day 4, the electrical capacitance of the cells decreases for treated sample as opposed to untreated samples. This reflects that the surface area of the BeWo b30 cells decreases when the samples were treated with forskolin.