Trans-Epithelial Electrical Resistance (TEER) is a critical parameter in the field of tissue engineering and cellular biology, providing insights into the integrity and permeability of cellular barriers. This post delves into the fundamental aspects of TEER, including its definition, how it works, and its common applications, aiming to offer a thorough understanding of this vital measurement technique.

What is TEER?

Trans-Epithelial Electrical Resistance (TEER) is a non-invasive, quantitative technique used to measure the integrity of tight junctions in cell cultures. It is an indicator of the permeability of cell layers, such as epithelial and endothelial barriers, which are crucial in maintaining the body's internal environment and facilitating selective transport mechanisms.

TEER Definition

TEER measures the electrical resistance across a cellular monolayer, reflecting the tightness of the junctions between cells. It is typically expressed in Ohm·cm², taking into account both the resistance of the cell layer and the surface area of the insert or well. High TEER values indicate a tight, impermeable barrier, while lower values suggest increased permeability.

How TEER Works

TEER measurement involves applying a small electrical current across the cell layer and measuring the voltage drop, which allows for the calculation of the electrical resistance. This process requires specialized equipment, such as a voltohmmeter and electrode setup, specifically designed for use with cell culture inserts.

1. Electrode Positioning: A pair of electrodes (one apical and one basal) is positioned on either side of the cell monolayer grown on a permeable support.

**Figure 1. Chopstick Electrodes Measurement**: This diagram illustrates using chopstick electrodes for TEER measurement, detailing the resistance components including the ohmic resistance of the cell layer, the cell culture medium, the semipermeable membrane insert, and the electrode-medium interface.

2. Current Application: A small AC current is applied between these electrodes.

3. Voltage Measurement: The resulting voltage drop across the cell layer is measured.

Figure 2. **Impedance Spectroscopy Concept**: Explains TEER measurement based on impedance spectroscopy, providing a clear understanding of impedance components involved in TEER measurement.

4. Resistance Calculation: The resistance is calculated using Ohm's law, with adjustments made for the surface area of the permeable support.

Figure 3. **Equivalent Circuit Diagram**: Offers an equivalent circuit diagram to analyze the impedance spectrum of cellular systems, aiding in the interpretation of TEER measurements

Common Applications of TEER

1. Barrier Integrity Assessment:

TEER is widely used to assess the integrity of epithelial and endothelial barriers in various tissues, including the intestinal, blood-brain, and pulmonary barriers. It helps in understanding how diseases, drugs, or other factors can affect barrier function.

2. Drug Permeability Studies:

In pharmaceutical research, TEER measurements help evaluate the permeability of compounds across epithelial and endothelial barriers, which is crucial for drug delivery and absorption studies.

3. Tissue Engineering:

TEER can monitor the development and maturation of engineered tissues, ensuring that created tissues mimic the natural barriers effectively.

4. Toxicology:

By assessing how substances affect barrier integrity, TEER measurements can indicate potential toxic effects of chemicals and pharmaceuticals on human tissues.

Advantages and Limitations

Advantages:

- Non-invasive and does not require cell labeling.

- Real-time monitoring of barrier integrity.

- Quantitative and reproducible

Limitations:

- Requires specialized equipment.

- Can be influenced by temperature, medium composition, and electrode placement.

- Not suitable for all cell types or conditions.

Conclusion

Trans-Epithelial Electrical Resistance (TEER) offers invaluable insights into the integrity of cellular barriers, serving as a cornerstone in tissue engineering, drug delivery, and toxicology studies. By understanding how TEER works and its applications, researchers can better investigate and manipulate the complex mechanisms governing cellular permeability and barrier function.

While this post provides a comprehensive overview, those interested in further details or specific research applications are encouraged to consult academic papers and textbooks specializing in cellular biology and bioengineering for deeper insights and methodologies.

Stretchable Microelectrode Arrays

The exploration of Trans-Epithelial Electrical Resistance (TEER) as a measure of cellular barrier integrity highlights the evolving landscape of cellular and tissue research. As we delve deeper into understanding the complexities of barrier function and its implications for health and disease, the integration of innovative technologies like soft and stretchable microelectrode arrays (sMEAs) emerges as a pivotal enhancement to research methodologies. sMEAs, by providing a soft and dynamic mechanical environment, offer a more physiologically relevant setting for cells compared to traditional rigid glass MEAs. This advancement ensures that measurements of TEER, and by extension, the insights gained into barrier integrity and permeability, more accurately reflect the natural behavior of cells in vivo. The utilization of sMEAs for recording and stimulation of extracellular electrophysiological activity in both tissue slices and dissociated cell cultures represents a synergistic approach to research that combines the precision of TEER measurements with the physiological relevance of sMEA environments. By adopting sMEAs, available through providers like BMSEED, researchers can enhance the fidelity of their models, ensuring that the data acquired offers a closer approximation to the complex dynamics of cellular barriers in living organisms. This integration of sMEAs into TEER-related studies promises to refine our understanding of cellular barriers, paving the way for breakthroughs in biomedical research and therapeutic development.

Trans-Epithelial Electrical Resistance (TEER): A Comprehensive Guide