transepithelial electrical impedance (teei) monitoring in a431 cells using electrode array

<meta charset="utf8"></head><body>Método TEEI para el análisis de electroporación y predicción de entregas en celdas A431

Electroporation is a technique in which cells are exposed to an electric field, creating temporary pores in the cell membrane through which cargos, including proteins, RNA, and DNA, can pass1,2. The most widely used version is bulk electroporation (BEP). BEP is performed by filling a cuvette with an electrolyte containing millions of cells, exposing the electrolyte to high voltage, and allowing cargo to enter the cells through diffusion or endocytosis1. There are many advantages to BEP, including high throughput and numerous commercially available systems. However, there are limitations to the BEP delivery. Inconsistent cell positioning relative to the electrodes and electric field shielding from adjacent cells causes significant variability in electric field exposure during BEP3,4. The high voltage required for BEP also has a significant negative impact on cell viability5. Since its inception in 20116, there has been growing interest in an electroporation method called porous substrate electroporation (PSEP), though it is sometimes referred to by other names, including localized electroporation and nano- or micro-electroporation1,7,8. In contrast to the cell suspension of BEP, PSEP is conducted on cells that are adherent to a porous substrate. Not only is an adherent state preferred for the majority of human cell lines9, but the pores in the substrate also focus on the electric current, localizing the transmembrane electrical potential (TMP) to specific regions of the cell membrane10,11. This localization allows for a significant reduction in applied voltage, decreasing damage and increasing cell viability. This combination of effects helps control cell membrane pore development, resulting in a more consistent and efficient delivery1,5,12.
A recent study introduced a PSEP device with a six-well, gold-plated electrode array for holding commercially available porous membrane inserts13 (Figure 1A,B), a practice that was first introduced by Vindis et al.14. The device can apply pulses and measure the electrical impedance across the cell monolayer, known as the transepithelial electrical impedance (TEEI), in real-time13. The user interface of the device allows complete control over the electroporation waveform and polarity. Importantly, real-time impedance measurements can be used to predict delivery outcomes without the need for expensive reagents or fluorescent markers, a concept known as label-free delivery15.
The PSEP platform consists of two major custom electrical components: the main body of the device, which houses the pulse generator and TEEI measurement equipment, and the electrode array, where the porous substrates are inserted, and the electroporation occurs. Diagrams for all custom electronics and 3D-printed components can be found at GitHub:&#160;https://github.com/YangLabUNL/PSEP-TEEI. In addition to the custom electronics, a computer is also required for the platform to function properly. The custom software requires MATLAB (version 2021a or later) to run, and Microsoft Excel to store and access data for analysis. The program controls the custom electronics and provides the graphical user interface (GUI) for adjusting settings. These programs were also made available at GitHub: https://github.com/YangLabUNL/PSEP-TEEI.
Preliminary data suggests this process is possible for different types of adherent cells (Figure 1C), but this article will only discuss the preparation of A431 cells using parameters that were found to be optimal for this cell line by Brooks et al.13. Additionally, because the propidium iodide (PI) cargo is cytotoxic, two experiments are performed, the first with a high concentration PI transfection media to quantify delivery efficiency, and the second with only cell culture media to measure TEEI over longer timescales. These experiments use identical electroporation waveforms, allowing the results to be correlated (Figure 1D).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/66971/66971fig01.jpg" /> 
Figure 1: Electrode array assembly diagram and foundational data. (A) CAD model of an insert inside a well of the electrode array. (B) CAD model of the electrode array. (C) Impedance increase due to PSEP for select cell lines, n = 3 per cell line. Error bar: standard error of the mean. (D) Delivery efficiency vs. TEEI increase correlation data. Delivery efficiency was calculated by dividing the number of cells labeled in both PI and calcein images from delivery experiments by the total number of cells identified with Hoechst. Cell count was determined using a custom CellProfiler pipeline, n = 6 per voltage. Error bar: (x- and y-axis) standard error of the mean. This figure is reproduced from Brooks et al.13 with permission. <a href="https://www.jove.com/files/ftp_upload/66971/66971fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<meta charset="utf8"></head><body>Autor destacado: Optimización de la electroporación de sustratos porosos a través de micro y nanocanales para mejorar el monitoreo y la caracterización de etapas i

Electroporación basada en sustrato poroso con monitoreo de impedancia eléctrica transepitelial

Our research is focused on improving porous substrate electroporation. Research has shown major benefits from using micro and nano channels to localize electroporation. But there are still questions to be answered, especially regarding monitoring and characterizing effects during the intermediate stages of the process.Some of the most recent developments include our use of trans-epithelial electrical impedance monitoring, as well as using nano channel based electroporation to create exosomes or measure tension in cell membranes. PSEP experiments still rely heavily on before and after fluorescent imaging to determine delivery and cell viability outcomes. Additionally, many PSEP based studies under report pulse parameters and very little research has been done to verify optimal parameters for common cell types.The primary research gap we address is the lack of reporting on the effects of PSEP during the cell recovery stage. However, our analysis of TEEI measurements correlated TEEI change with viability and delivery efficiency, which allowed us to identify optimal PSEP waveform parameters as well. Our primary focus moving forward will be to identify the mechanisms causing the TEEI increase.Ideally, those findings will help us fine tune the PSEP process for an even more efficient delivery.

Monitoreo de impedancia eléctrica transepitelial (TEEI) en celdas A431 mediante guía de electrodos

transepithelial-electrical-impedance-teei-monitoring-a431-cells-using

Research

JoVE Journal

Bioengineering

Transepithelial Electrical Impedance (TEEI) Monitoring in A431 Cells Using Electrode Array

29 Views. To begin, pipette 1.5 milliliters of the 0.1 milligram per milliliter propidium iodide solution into each well in the electrode array. Place an insert into each well in the electrode array, fitting the feet of the insert into the alignment grooves so the insert is flush with the upper surface of the well. Screw the top electrode printed circuit board to the top of the electrode array wells and connect the electrode array to the porous substrate electroporation, or PSEP device.Place the...