How It Works
The ECIS in Action
Introduction (Back to Top)
Testing drugs, chemicals, cosmetics, and other products on animals is necessary but not entirely palatable, and not just for humane reasons. Animal upkeep is expensive, results are not always reliable, and a lot of work is involved in getting a single data point.
About ten years ago, Molecular Dynamics Inc. (formerly of Menlo Park, CA, now of Crawley, UK), came up with a solution: the silicon microphysiometer. This device employed pits and valleys etched in silicon for testing the physiologic response of single cells to chemicals and drugs. Unfortunately, the microphysiometer did not revolutionize pharmaceutical testing as was originally hoped, most likely due to the unfamiliar format and limited capability of the device, which measured lactate release from cells.
Now, a Rensselaer Polytechnic Institute (RPI; Troy, NY) Industrial Incubator company has taken single-cell testing to a new level. Applied Biophysics (ABP), founded by Nobel Prize-winning physicist Ivar Giaever and RPI senior researcher Charles Keese, has commercialized a technology that may finally take the animal out of animal testing. ABP's Electric Cell-Substrate Impedance Sensing, or "ECIS 100" for short, uses electrical response to study complex cell behavior.
"Using the new electric biosensor instead of the traditional petri dish and microscope to study cells offers unprecedented sensitivity and detailed results, while presenting researchers with a noninvasive technique for testing animal cells," says Giaever. The ECIS provides data as frequently as every quarter-second to follow a cell's behavior. "By electronically eavesdropping on cells, we can examine and measure the activity of live cells over time. This is an entirely new way of doing tissue culture. Because the system is computer-based, highly quantitative data can be gathered in real time, 24 hours a day, with minimal lab time and personnel involved."
Most importantly, the ECIS gives more reliable, more comprehensive data than animal testing. According to Giaever, fundamental cell measurements impact many areas of cell research, including in vitro toxicology, pharmacology, and understanding a cancer cell's metastatic potential. Live cells are electronically cultured in tiny trays equipped with eight holding bays with its own low alternating current delivered via a tiny gold electrode. When electricity is present a cell will spread out over the electrode, which opens it up for real-time measurements. Scientists can also use the instrument to learn how other cells react to repair a wounded cell.
The ECIS 100 is a complete, ready-to-use system that includes both a dedicated tissue culture incubator and a dedicated computer. The software runs on a Windows 98 platform and manages all data acquisition, storage, and analysis.
How It Works (Back to Top)
In ECIS, cells are cultured upon small gold electrodes, and their impedance is measured as a function of time with a low AC current. The impedance can be sampled as often as every 1/4 second to as slow as once an hour. The measured impedance reflects the activities of cells on the electrodes. Cell densities ranging from a heavy confluent layer to single isolated cell can be used. With unprecedented sensitivity, ECIS measures the changes in cell morphology and motion as a function of time.
In the ECIS, cells grow on and around a gold electrode (center, green-colored in photo).
These fundamental measurements impact many areas of cell research including:
- dynamics of cell attachment and spreading
- determination of the barrier function of endothelial and epithelial layers
- in vitro toxicology
- single cell studies
- G protein-coupled receptor signal transduction
- metastatic potential of cells
- cell receptor-ligand interactions
The ECIS in Action (Back to Top)
ECIS has shown tremendous potential for in vitro toxicology. Following is a preliminary study of the toxic effects of acetaminophen on HEPG2 liver cells.
Each well was precoated with laminin and then rinsed 2x with medium. Acetaminophen solutions were first added to each well (300 microliters) and then the same volume of cell suspension (giving 1.5 x 105/cm2). Electrode number 8 (the gray trace) is the control receiving no acetaminophen. The highest concentration of the compound completely blocks cell attachment and spreading, while the other concentrations have intermediate effects.
Acetaminophen concentrations in each well:
1.............10,000 microgram/ml acetaminophen
2...............5,000 microgram/ml acetaminophen
3...............2,500 microgram/ml acetaminophen
4...............1,250 microgram/ml acetaminophen
5..................625 microgram/ml acetaminophen
6..................313 microgram/ml acetaminophen
7..................155 microgram/ml acetaminophen
Frequency is 4000 Hz, amplitude is 1 Volt and sampling time is 1 minutes
Ivar Giaever and Charles Keese in their laboratory.
Giaever and Keese founded Applied Biophysics Inc. at the Rensselaer Incubator Center in 1993. Since then, they've licensed the ECIS technology for commercial use and have sold more than 20 systems worldwide. Giaever recently presented his research at the American Association for the Advancement of Science annual meeting in Anaheim, CA, in January.
For more information: Ivar Giaever, President, Applied BioPhysics Inc., 1223 Peoples Ave., Troy, NY 12180-3535. Tel: 518-276 2165. Fax: 518-276 6380. Email: firstname.lastname@example.org.
By Angelo DePalma