Brain on a chip
October 16, 2002
Zombie brains could soon become a powerful tool for drug developers. A
biotech company has developed a way to keep slices of living brain tissue
alive for weeks, allowing researchers to study the effect of chemicals on
entire neural networks, not just individual cells.
"We are building stripped-down mini-brains, if you will, directly on a
chip," says Miro Pastrnak, business development director of Tensor
Biosciences of Irvine, California. He says the "brain-on-a-chip" could help
drugs developers find better treatments for a host of neurological and
psychiatric disorders, from Alzheimer's disease to schizophrenia. Tensor may
already have found a more effective treatment for anxiety this way.
"Behaviour is the result of the electrical activity of billions of brain
cells connected in complex circuits, not the activity of a cell or a
receptor acting in isolation," says Pastrnak. And psychoactive drugs alter
behaviour at this level, often affecting many different types of neural
receptors, cell types and synapses. Yet at the moment, candidate drugs are
only tested on individual nerve cells, because it's proved difficult to keep
larger pieces of brain tissue alive for more than a few hours.
The mini-brain, however, survives for weeks at a time. "We can even
co-culture tissues from different parts of the brain on the same chip to
examine the communication between them," says Pastrnak.
It consists of a glass chip containing tens of thousands of
interconnected living brain cells, taken from rats or mice and suspended in
a solution of artificial cerebral fluid. An array of 64 electrodes on the
chip's surface monitors the overall electrical activity of the brain tissue,
just like an electroencephalogram (EEG), to show the effect that drugs have
on the tissue.
Tensor's electrodes maintain continuous contact with the cells but do not
damage them. This is vital when repeating experiments, because you have to
be sure you are always getting readings from the same groups of neurons.
Neurophysicist Peter Fromherz of the Max Planck Institute for
Biochemistry in Martinsried, Germany, who has developed techniques to grow
neurons on silicon, says the chips would be even more useful if they could
record the activity of individual neurons. "The problem is that these
electrodes are widely spaced, so you get little information about the neural
circuits," he says.
But the 64 electrodes are enough to get useful EEG readings even if you
can't tap into the electrical activity of single neurons, Fromherz says. And
Tensor has also developed a way to produce the natural EEG rhythms, or
brainwaves, in its chip. The rhythms continue even after the chemical that
induces them has been washed off. Fromherz thinks that the chip will indeed
provide a powerful new tool for testing the effect of drugs.
At next week's Chips to Hits conference in Philadelphia, Tensor
Biosciences will announce that it has already used its chip to find a
potential drug for anxiety that it believes will be more specific, less
toxic and have fewer side effects than existing drugs.
New Scientist issue: 19 October 2002
|
