EVOM™ Manual Meter for TEER Measurement with Auto Data Logging

The blank feature is used when you want to subtract out any measurement that is not from the membrane, such as the electrode and fluid resistances.

No, TEER measurement requires an area calculation. To compute TEER, multiply the measured resistance by the appropriate surface area (below). For example, a 12 mm insert measures 565 Ω, the TEER is 565 Ω × 1.13 cm2 = 638.5 Ω- cm2. Here are the surface areas generally applicable to different transwell/insert formats: 6 well plate (24 mm inserts) 4.52 cm2, 12 well plate (12 mm inserts) 1.13 cm2, 24 well plate (6.5 mm inserts) 0.33 cm2, 96 well plate (4.3 mm inserts) 0.14 cm2. For Automated TEER Measurements, consider using the WPI REMS Automated TEER Measurement System.

Clear any data in memory by opening settings, store menu then press new plate, that will clear any prior readings. Return to the main screen, open the preview screen, select each well to measure (the selection turns green), place the electrode, then measure. When you’re done measuring the selected wells, open the settings, press the store screen menu, then press store new to save the plate data to the USB drive.

Take the EVOM™ Manual out of the laminar hood after use. Next time, turn on the UV inside the hood. Once the hood is disinfected by UV, turn off UV, next spray 70-100% ethanol or isopropanol onto a paper towel and wipe the EVOM™ Manual. Do not spray alcohol directly onto EVOM™ Manual.

You can expect to see a change of raw resistance values. However, you subtract the blank values (blank Transwell with no cells) from the sample values (Transwell with cells). This way, you subtract the blank value with increased volume from samples with increased volume. Thus, any change of resistance contributed by increased volume is omitted. Consistently use the same volumes for all your samples in an experiment.

Drift–Readings that continuously increase or decrease significantly (either voltage or resistance) over time. Example: At 1000 Ω, the reading is increasing 100 Ω/ minute. (A drift of 10 Ω/minute is acceptable.) Excessive drift may be caused by changes in the pH or temperature, or the electrode needs cleaning.

There are a few things that can be a possible cause of this drift.

• Ensure that the electrodes are fully immersed in culture media solution, and the fluid temperature in the plate is consistent by equilibrating at room temperature or using a plate warmer.
• Another common cause of drift is the electrode tips may have deposits of cell culture media constituents
• The electrode (tips) requires enzymatic cleaning (Tergazyme or Enzol) periodically up to 1x per week depending on the use.
• Handheld electrodes also must be kept as motionless as possible during a measurement.
• Excessive movement will cause the measurement to fluctuate.
• Additionally, in a 5% CO2 environment, a loss of CO2 causes the media pH to change, and the resistance reading may change. This is mainly applicable in the context of continuous measurement for an extended period (hours, as compared to a few minutes).

Temperature is known to affect TEER values. We recommend that you maintain a consistent temperature to obtain consistent values. Since the readings are obtained in cell culture media/ buffer. We recommend that you use a water bath with a fixed temperature to warm the media/buffer to be used during the experiment. A consistent media/buffer temperature ensures a consistent experimental condition. We recommend taking the well plate, containing cells grown on culture inserts, out of the incubator for at least 20 minutes to stabilize the well plate at room temperature before making measurements. 

If you are using an EndOhm chamber, make sure you maintain the same fixed distance between the top and bottom electrodes to obtain consistent read outs. If you are using a chop-stick electrode (STX2), try to hold it in a vertical position while obtaining results. Consistency in maintaining the same holding position of the chop-stick electrodes while performing an experiment is expected to show consistent read outs.

We recommend using the same fluid with the same ionic concentration both in the apical (e.g., top of a cell culture insert) or basolateral side (e.g., lower part of the cell culture insert sitting inside a well of a 12 well-plate). During the measurement, if you are using 1X PBS buffer in the apical side, we recommend using 1X PBS buffer in the basolateral side. We also recommend that both fluid levels (inside and outside of cell culture inserts) be at the same height in order to minimize pressure differentials. During experiments, the apical well/side is filled first with fluid to prevent dislodging of the membrane from the filter by hydrostatic pressures.

Application of consistent volumes of the fluid (media/buffer) during all experiments will reduce data variability.

The EVOM2 works on the principle that once you measure what we call the “blank” well, this first resistance measurement contains the summation of the electrode resistance, the electrode gap and the resistance due to the volume and the molarity of the liquid media. (Any electrode charge differences are negated by the EVOM2's measurement method of reversing the polarity and averaging the results.)

The successive periodic measurements of the well are a plot of the growth of the membrane by a resistance measurement, and once this resistance graph has plateaued, we can say that the membrane has reached confluence. The EVOM2 system works just like a Voltage clamp amplifier and Ussing system, but without the special Ussing chamber.

The EVOM2 system is not as accurate as an Ussing can be, but the purpose of the EVOM2 system is to determine if a membrane is confluent, not perform detailed analysis. (Some membrane permeability analysis can be studied by the EVOM2  system, but as a percent of change rather than an absolute value of change.)

Several experimental variables influence TEER results, such as:

• Temperature,
• Electrode condition and positioning,
• Cell type and culture conditions,
• Medium composition

Because cells grow and form a tight monolayer. Initially TEER is low after seeding, then increases as cells multiply and cover membrane gaps, forming a confluent barrier.

TEER is widely used to evaluate cell barrier function and permeability in: drug permeability and absorption studies, blood-brain barrier research, toxicity and cytotoxicity testing, and tissue and cell culture monitoring.

No — TEER is non-destructive. It allows repeated measurements over time to monitor barrier integrity without harming cells.

High TEER → Strong, intact cell barrier.

Low TEER → Weak or permeable cell layer.

In some models (e.g., alveolar cells), buffer/media may be required for accurate measurement.

No. TEER is resistance normalized by cell growth area (Ω·cm²), calculated from the raw resistance reading.

Do NOT hold the electrode by the cable. It can physically break the internal connections gradually.

Hold the electrode by the arrowed region (plastic).

Limit liquid immersion or liquid spray level somewhere up to here (maximum). You do not want the liquid to get inside and reach up to internal the cables or connectors that’s why. You can wipe with the rest of the electrode with a paper towel sprayed with isopropanol or ethanol (do not spray directly).

If you experience instability at 500 Ω, the reading jumps from 450 to 550 Ω and does not settle down (an instability ±5 Ω is acceptable in the 500 Ω range). In the higher ranges, up to ±1000 Ω is acceptable at the 100K range. Electrodes showing instability may require enzymatic cleaning.

• The most common causes of reading instability can be fixed by fully immersing the tips in solution or performing enzymatic cleaning.
• The electrode tips are not fully immersed in adequate conductive liquid (media or buffer). Add extra liquid to bring the liquid level up to the electrode tips. (Use consistent apical and basolateral volumes to make consistent comparisons.) The electrode tips (sensing region) may have deposits of cell culture media constituents, this can be resolved with enzymatic cleaning.

Yes, we have two sets of EndOhms. The Legacy EVOM2 EndOhms (ENDOHM-6G, ENDOHM-12G, ENDOHM-24G-SNAP) use the 53330-01 cable, and the newer EndOhms (EVM-EL-03-01-0x) which are compatible with the EVOM™ Manual use the 99916 cable.