manufacturer :       WPI

model :                   EVOM

annotation :           Dokumente engl.

TEER Measurement

Trans Epithelial Electric Resistance (TEER) Measurements

During the last two decades TEER measurements have become universally established as the most convenient, reliable and non-destructive method to evaluate and monitor the growth of epithelial tissue cultures in vitro.
The confluence of the cellular monolayer is quickly determined by a sharp increase in TEER. Recently there has been a significant surge of interest in introducing a combined electrode for resistance measurements in the Millipore 96-well PAMPA (parallel artificial membrane permeability assay) plate.
TEER measurement technology, which was first introduced by WPI in the mid-1980's, has since been perfected and expanded to include a range of TEER related manual and automatic instrumentation.

• Manual TEER measurement of epithelial cells in 24- and 96-well plates
• Battery powered electrically isolated meter
• AC current avoids adverse effects on tissue
• Compatible with Endohm chambers
• STX2 manual electrode enclosed with meter
• STX2 can be sterilized with EtO, alcohol or a bactericide

The EVOM was the first instrument designed specifically to perform routine TEER (Trans Epithelial Electric Resistance) measurement in tissue culture research.
The battery-powered EVOM produces an AC current that avoids adverse effects on tissues, which can otherwise be caused, by a DC current -- including electrode metal deposits.

The EVOM has an easy-to-read LC display and is also available with a BNC recorder output (EVOMX). Input impedance of the EVOM is greater than 1010 ohm, and resistance ranges from 0 to 1999 ohm; and 0 to 20,000 ohm can be monitored using the switchable range setting located on the instrument front panel.

One unique feature of the EVOM is that resistance readings are unaffected by membrane capacitance and membrane voltage. The membrane voltage reading range is ±200 mV. EVOM comes complete with the popular STX2 "Chopstick" electrode set. The STX2 consists of a fixed pair of double electrodes, 4 mm wide and 1 mm thick.
Each stick of the electrode pair contains a silver/silver-chloride pellet for measuring voltage and a silver electrode for passing current. The small size of each electrode is designed to facilitate placement of the electrodes into cell culture wells.
STX2 can be used with all tissue culture inserts currently on the market. For more accurate quantitative measurements and/or for lower resistance measurements (e.g., endothelial tissue cultures) the EVOM can be used in conjunction with the optional Endohm chambers.

• BNC output for Data Acquisition System
• Toggle switch for continuous measurement

EVOMX is a modified version of the EVOM and is recommended for use with STX100 series electrodes. Its measurement switch and circuits have been modified to remain ON continuously.
This enables the user to have one hand free to move the electrode while using the other to note the readings. A BNC recorder output connector is provided on the EVOMX to permit direct recording of TEER measurements to a chart recorder or computer-based data-acquisition system.

STX100 Electrodes

• Designed for 24-well HTS plate (Corning Costar and BD Falcon) and with 96-well plates (Millipore and BD Falcon)
• Improved accuracy down to 5 Ohm
• Sterilized with EtO, alcohol or bactericide

With the development of a High Throughput Screening (HTS) protocol for faster drug discovery, a new line of cell culture filter plates have been introduced by several major cell culture insert manufacturers.
These HTS plates normally have either 24 or 96 individual cell culture inserts "bonded" together as one plate so that it can be handled by a robot apparatus. In response to these developments, WPI has developed an automatic REMS system and a manual electrode, STX100, for TEER measurements using HTS plates.
STX100's design is based on the same reliable design principle as the universally used STX2 electrode, with several important modifications. The size of the electrode tip has been reduced to 1.5 mm to facilitate positioning through the narrower slit of the HTS plate. The STX100 electrode itself is constructed using a stronger material for higher durability and maximum usage applications. The bottom section of the electrode is shaped to fit neatly into the "keyhole" shaped filter well.

This enables the STX100 electrode to produce increased accuracy and reproducibility of TEER readings (±5?) compared to the standard STX2. Several versions of STX100 are available, designed to fit the Corning Costar 24-well HTS plate, the Falcon 24 well HTS plate, the Millipore Multiscreen CaCo 96-well plate, and BD Falcon HTS 96-multiwell plate. Measurement can be directly performed when the HTS plate is in either a common or divided tray, reducing the possibility of contamination as well as mechanical damage to the cultured cells.