Background noise reduced
In the new chip, the amplifiers are smaller, permitting the signals of all 20,000 electrodes to be amplified and measured at the same time. However, the smaller amplifiers have higher noise levels. So, to make sure they capture even the weakest nerve impulses, the researchers included some of the larger and more powerful amplifiers into the new chips and employ a nifty trick: they use these powerful amplifiers to identify the time points, at which nerve impulses occur in the cell culture dish. At these time points, they then can search for signals on the other electrodes, and by taking the average of several successive signals, they can reduce the background noise. This procedure yields a clear image of the signal activity over the entire area being measured.
In first experiments, which the researchers published in the journal Nature Communications, they demonstrated their method on human iPS-derived neuronal cells as well as on brain sections, retina pieces, cardiac cells and neuronal spheroids.
Application in drug development
With the new chip, the scientists can produce electrical images of not only the cells but also the extension of their axons, and they can determine how fast a nerve impulse is transmitted to the farthest reaches of the axons. “The previous generations of microelectrode array chips let us measure up to 50 nerve cells. With the new chip, we can perform detailed measurements of more than 1,000 cells in a culture all at once,” Hierlemann says.
Such comprehensive measurements are suitable for testing the effects of drugs, meaning that scientists can now conduct research and experiments with human cell cultures instead of relying on lab animals. The technology thus also helps to reduce the number of animal experiments.
The ETH spin-off MaxWell Biosystems is already marketing the existing microelectrode technology, which is now in use around the world by over a hundred research groups at universities and in industry. At present, the company is looking into a potential commercialisation of the new chip.