Neurological Biosensor Chip MeasuresElectrical Activity in Living Cells

Originally Published MDDI April 2003

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Neurological Biosensor Chip Measures Electrical Activity in Living Cells

In February, researchers in Germany announced their success in directly connecting a newly developed biosensor chip with living nerve cells. They were then able to read electrical signals produced by the cells. According to scientists at Infineon Technologies (Munich), the newly developed Neuro-Chip will allow new insights to be gained into the biologic function of neurons, nerve tissue, and organic neural networks. They believe that the device ultimately will lead to improved testing during drug development. The technology will be used to assess the effects of new pharmaceutical compounds on living neurons, contributing to greater efficiency and productivity in research. Infineon collaborated with the Max Planck Institute of Biochemistry (MPI; Martinsreid, Germany) to develop the technology.

Infineon's efforts were focused on semiconductor technology development, and MPI provided specialized expertise in the field of neuron-chip interfacing. MPI director Peter Fromherz explains, “That our long-lasting basic research on neuron-semiconductor interfaces [has led to] a high-tech chip is like a dream coming true.” 

The Neuro-Chip integrates 16,384 sensors in a 1-mm2 array pattern. Each sensor is separated by 8 µm. This density is approximately 300 times greater than that of traditional methods for studying neurons. Classic techniques use glass substrates with vapor-deposited metallic lanes to contact the neuron. Because the typical size of neurons is 10–50 µm, low-density sensors may not establish a reliable contact. The high-density sensor array ensures that each neuron in a sample is contacted by at least one sensor.
 
Electronic circuitry surrounding the sensors amplifies and processes the neuron signals, which are extremely weak. Individual neurons are placed in a nutrient solution above the sensor array, which keeps the neurons alive and allows nerve tissue reconstruction. Conventional research methods can damage neurons. The new method, on the other hand, allows undisturbed observation of nerve tissue over several weeks. 

Because the Neuro-Chip surveys several neurons at the same time, more statistically relevant data are available. The chip also enables recording of the operating sequence of electrical activity within nerve tissue over a defined time. More than 2000 single values can be recorded every second for each of the chip's 16,384 sensors. The generated data can then be converted into a color image for visual analysis. These data can be used to determine how complete nerve tissues react to electrical stimulation or to certain chemical substances in a given period of time.

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