Biosensor chip expands neuroscience horizons

Electronic Products ^ | April, 2003 | Christina Nickolas

[BraveMan]

A biosensor chip that measures electrical activity in living cells promises both new techniques for neuroscience and the ability to develop new drugs by testing them on living neurons.

Infineon Technologies (Munich, Germany) and Max Planck Institute (MPI) of Biochemistry (Munich, Germany) have succeeded in connecting a newly developed biosensor chip with living neurons and in reading electrical signals produced by the cells. Introduced at the recent International Solid State Circuits Conference in San Francisco and named Neuro-Chip, this chip promises to allow neurobiological and neurochemical researchers to gain new insights into the biological function of human neurons, nerve tissue, and organic neural networks.

In addition, the chip will help develop new drugs by enabling tests of pharmaceutical compounds on living neurons. Infineon is responsible for the semiconductor technology and MPI for interfacing neurons to the chip. The first tests measured electrical signals from live neurons of snail brains.

The Neuro-Chip integrates 128 x 128 sensors into an array pattern covering just 1 mm2 . A sophisticated electronic circuit is integrated below each sensor to amplify and process the weak electrical signals (5 mV max) of neurons. Individual neurons are placed into a nutrient solution above the sensor array, keeping the neurons alive while allowing reconstruction of nerve tissue.

With 16,384 tiny sensors packed into 1 mm2 , Infineon Technologies' Neuro-Chips will monitor the electrical activity of living neurons. The Neuro-Chip is connected with a living cell.

The sensor density of the Neuro-Chip is about 300 times greater than today's common methods for studying neurons, which use glass substrates with vapor-deposited metallic lanes to contact the neuron. Each sensor on the chip is separated by a distance of 8 µm to ensure that each neuron--whose typical size is between 10 and 50 µm--in a sample is contacted by at least one sensor.

The chip checks several neurons at the same time and records the operating sequence of electrical activity within nerve tissue over a defined time. The Neuro-Chip can record more than 2,000 single values from each of its 16,384 sensors.

The data are then transformed into a color picture from visual analysis. Scientists can use the data to see how nerve tissues react over time to electrical stimulation or some chemical substance.

The 5 x 6-mm CMOS chip includes circuitry to amplify and process the neuron signals and to transmit the data off chip. The method allows researchers to follow the functionality of how the nervous system and brain learns, processes, and stores its learning for a period of several weeks without damaging the neurons compared with previous methods. For more information visit http://www.infineon.com.

[BraveMan]

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