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TEER Measurement |
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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.
Multi-96
Resistance measurement with 96-well PAMPA (parallel artificial membrane
permeability assay) plates
Non-cell based 96-well PAMPA assays have been designed for predictive
drug candidate testing. To ensure that the donor/acceptor fluxes are
not due to porous or unstable hexadecane layers, the stability of the
hexadecane membrane can be tested at the end of the incubation period
by electrical resistance measurements.
To conduct the measurement a PAMPA plate is transferred to MULTI-96.
Like the other Endohm models (designed for individual cell culture
cups), the base of MULTI-96 is a fluid- filled receptacle for the PAMPA
plates, also serving as the bottom half of the electrode pair.
Inserting the top electrode into each well allows the user to obtain
the resistance of the synthetic membrane layer of that well. MULTI-96
provides a stable and reproducible reading of tissue culture
resistance. EVOMX is recommended for use with MULTI-96.
ENDOHM
TEER measurement of endothelial cell cultures in individual cups
Compatible with EVOM and EVOMX
Improved accuracy of 1-2 Ohm
Accommodates 6mm, 12mm, 24mm cups and Costar Snapwell cup
Sterilized with EtO, alcohol or a bactericide
Using WPI's EVOM resistance meter, Endohm chambers provide reproducible
resistance measurements of endothelial tissue in culture cups. Transfer
cups from their culture wells to the Endohm chamber for measurement
rather than using hand-held electrodes. The chamber and the cap each
contain a pair of concentric electrodes: a voltage-sensing
silver/silver chloride pellet in the center plus an annular current
electrode.
The height of the top electrode can be adjusted to fit cell culture
cups of different manufacture. Endohm's symmetrically apposing circular
disc electrodes, situated above and beneath the membrane, allow a more
uniform current density to flow across the membrane than with STX2
electrodes. The background resistance of a blank insert is reduced from
150 Ω (when using WPI's hand-held STX2 electrodes) to less
than 5 Ω.
With Endohm's fixed electrode geometry, variation of readings on a
given sample is reduced from 10-30 Ω with STX2 electrodes
(depending on the experience of the user) to 1-2. Compared with other
resistance measurement methods, Endohm with EVOM offers a much more
con-venient and economic solution to "leaky tissue" measurement.
Because of the uni-form density of the AC square wave current from
EVOM, errors owing to electrode polarization or membrane capacitance
are largely eliminated.
Endohm together with EVOM offers the most accurate and economical
endothelial ohmmeter now avail-able. To date, cups from Costar,
Millipore, ICN Biomedicals, and Falcon have been tested. Endohm
chambers may be sterilized with EtO, alcohol or a bactericide (also
Cidex, Microsurgery section); not autoclavable.
Automated TEER Measuring System
The REMS AutoSampler automates measurements of electrical resistance of
transepithelial, transendothelial or Caco-2 cell membranes being grown
to confluence on microporous filters of high throughput screening (HTS)
24- and 96-well microplates. It is a PC-controlled, tissue resistance
measurement system that offers reproducibility, accuracy, flexibility
and ease-of-operation for this kind of measurement.
Automated measurement of tissue resistance in cell culture microplates
provides the important advantages of speed, precision, decreased
opportunity for contamination and the instant availability of measured
resistance data on a computer. These measurements are useful in
applications such as drug bioavailability studies and studies on the
mechanisms of drug transport.
The main components of the REMS AutoSampler include: the robotic
sampler that moves the electrode over each well of the microplate, the
electrode which is located on the robotic arm, a base plate for the 24-
and 96-well tray, a Windows-based data acquisition card, the REMS
interface unit and the REMS software to operate the system on a
Windows-based computer.
The REMS AutoSampler automates TEER measurements previously made with
WPI's EVOM Epithelial Voltohmmeter. Automated tissue resistance
measurements up to 20 kΩ can be performed on 24- or 96-well
HTS microplates. Microplates presently supported include the Corning
Costar HTS Transwell-24, Falcon HTS Multiwell insert systems, and
Millipore Multiscreen™ CaCo 96-well plate.
The REMS AutoSampler is designed to facilitate integration with other
robotic systems. Special locating bars are installed on the REMS base
platform that allow other system robots to place an HTS tray into a
precise location on the REMS base.
The REMS AutoSampler will automatically measure and record tissue
resistance from a user-specified matrix of culture wells on the
microplate. According to the specified sequence, the robotic arm moves
over the identified wells taking TEER measurements. By means of a x-y-z
locating system, the electrode-containing arm is positioned precisely
and reproducibly over each well.
The ability of the REMS AutoSampler to reproducibly and precisely
locate the electrode results in highly reproducible TEER measurements.
TEER measurements are stored in the computer as the electrode moves
from one well to the next. The Windows-based software provides
user-friendly features to acquire, display and store the tissue
resistance measurements.
The REMS electrode is very compact and robust in design. Each of two
rod-shaped probes, 1.5 mm in diameter, consists of a pair of
electrodes: one electrode for injecting current and the other for
measuring the voltage. The use of two pairs of electrodes eliminates
the error caused by the electrode-liquid interface.
To take a measurement, the robot inserts one probe into the center of
the filter well and the other into the opening slot of the 24- or
96-well plate. The use of AC current to measure resistance provides
several advantages over DC current, including:
Absence of offset voltages on measurements;
There is a zero net current being passed through the membrane and
therefore it is not adversely affected by a current charge;
No electrochemical deposition of electrode metal.
The REMS AutoSampler also features a rinse and calibration check
station. If occasional rinsing of the REMS electrode is required it may
be sent to a rinse station by pressing the rinse station button on the
menu bar. The rinse station can also function as a calibration check
station when fitted with a calibration cell containing a synthetic
membrane (WPI's optional CALICELL-HTSF).
The use of this calibration cell, which mimics a confluent epithelial
membrane's resistance in fluid, provides a quick and effective test to
determine when the REMS measurement system is fully initialized
following start-up and to check its functionality during operation.
Give your HTS system the ability to perform REMS TEER
measurements
WPI's REMS TEER measurement system is also available in a fully
customizable package that does not include the robot. The REMS-KIT is
designed to enable manufacturers and users of robotic and HTS systems
to incorporate TEER measurement capability into their own automated
protocols. Essentially the REMS-KIT provides the same TEER measuring
system as the REMS but without the robot positioner.
Control over TEER measurement is accomplished using the DDE protocol.
Virtually any Windows-compatible programming language that uses the DDE
protocol (including LabView and Visual Basic) can be used.
The REMS-KIT is designed for use with Corning Costar HTS Transwell-24,
Falcon HTS Multiwell Insert System and Millipore MultiscreenTM CaCo
96-well plates. The system includes the following components:
- REMS TEER electrode with 5-ft cable
- Dummy TEER electrode for training robot
- REMS TEER measurement electrode interface unit
- Windows PCI A/D data acquisition card
- Interface software using the DDE protocol
- Instruction Manual
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Last Updated ( Tuesday, 12 January 2010 )
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