Abstract
Barrier tissue protects the body against external factors by restricting the passage of molecules. The gastrointestinal epithelium is an example of barrier tissue with the primary purpose of allowing the passage of ions and nutrients, while restricting the passage of pathogens and toxins. It is well known that the loss of barrier function can be instigated by a decrease in extracellular calcium levels, leading to changes in protein conformation and an increase in paracellular transport. In this study, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetra acetic acid (EGTA), a calcium chelator, was used to disrupt the gastrointestinal epithelial barrier. The effect of EGTA on barrier tissue was monitored by a novel label-free method based on an organic electrochemical transistor (OECT) integrated with living cells and validated against conventional methods for measuring barrier tissue integrity. We demonstrate that the OECT can detect breaches in barrier tissue upon exposure to EGTA with the same sensitivity as existing methods but with increased temporal resolution. Due to the potential of low cost processing techniques and the flexibility in design associated with organic electronics, the OECT has great potential for high-throughput, disposable sensing and diagnostics.
Highlights
Understanding and controlling the barrier function of epithelial tissue is of great importance for pharmaceutical research and drug development, as well as having applications in diagnostics and fundamental research
Upon a decrease of extracellular calcium concentration due to the presence of EGTA, the organic electrochemical transistor (OECT) rapidly senses the breach in the epithelial cell layer in a concentration dependent manner
We validated these results by comparison with traditional techniques such as immunofluorescence, transepithelial resistance (TER) measurement and a Lucifer Yellow permeability assay, and found that the data correlates with the results obtained using the OECT
Summary
Understanding and controlling the barrier function of epithelial tissue is of great importance for pharmaceutical research and drug development, as well as having applications in diagnostics and fundamental research. Manipulating barrier function is primarily applicable in targeted drug delivery, which involves the specific transport of a molecule across the lumen to the underlying tissue. The function of some proteins such as cadherins, are sensitive to the concentration of extracellular calcium Cadherins, found in both the adherens junction and the desmosome contain multiple calcium binding domains [14]. We use Caco-2 cells grown on permeable transwell filters When cultured in this format, these cells are known to form polarized monolayers with an apical brush border, similar to that found in the human colon [17]. To mimic this effect in vitro, we exposed Caco-2 monolayers to EGTA (Ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetra acetic acid), a specific calcium chelator. We validate the OECT results with traditional characterization techniques, including immunofluorescence staining of junctional adhesion proteins, permeability assays and measurement of transepithelial resistance (TER)
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