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Article:
Light-sensitive plastic might be key to repairing damaged retinas. Creating
neuro-prosthetic devices such as retinal implants is tricky because
biological tissue
doesn't mix well with electronics. Metals and inorganic semiconductor
materials can
adversely affect the health or function of nerve cells, says Fabio
Benfenati at the
Italian Institute of Technology in Milan. And over time the body's natural
defences can
be incredibly hostile and corrosive to such materials.
The emergence of flexible, organic semiconductor materials now offers an
alternative. To
test them, Benfenati and colleagues seeded nerve cells onto the surface of
a
light-sensitive semiconducting polymer similar to those used in some solar
cells. The
cells grew into extensive networks containing thousands of neurons. "We
have proved that
the materials are highly biocompatible," says Benfenati.
What's more, the presence of the cells did not interfere with the optical
properties of
the polymer. The team were able to use the neuron-coated polymer as an
electrode in a
light-driven electrolytic cell. Artificial colour vision
When short pulses of light were aimed at specific sections of the polymer,
only local
neurons fired, suggesting the material has the spatial selectivity needed
for artificial
retinas, says Benfenati.
"It's very elegant science," says Robert Greenberg, whose company Second
Sight is close
to receiving clinical approval for its retinal prosthesis. But Greenberg
questions
whether the electrical currents generated would be sufficient to stimulate
nerve cells
in the eye.
It's still too early to tell, says Benfenati. But he thinks the new
material is worth
further study, because of another benefit. It can be tuned to respond only
to specific
wavelengths of light, raising the prospect of creating artificial colour
vision, he
says.
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