June 26, 2004.
By Gabe Romain,
An implantable chip that can serve as both a prosthetic retina and a drug delivery system has been developed to treat age-related blindness and conditions such as Parkinson's disease.
Created by researchers at the Stanford University School of Medicine in California, the chip communicates chemically rather than electrically, using neurotransmitters to stimulate cells.
"People believed that a neurotransmitter device could not be done, in the sense that it wasn't possible to deliver such small volumes of chemicals, but we show that it is possible and that further research along these lines should be done," says Stanford researcher Harvey Fishman.
The new implant, plans for which were first widely reported last December, is considered a big improvement over existing devices.
Existing implants work by converting light into electrical signals that the optic nerve then transmits to the brain.
The problem with electronic implants, however, is that it's hard to make them work properly with the body.
Whereas most artificial retinas use electrodes to stimulate nerve cells in the eye, the new prototype uses an implant that releases neurotransmitters like a natural retina.
This allows for graded responses to activation, say the researchers, enabling a more complex range of signals than the simple on and off capabilities of electrical devices.
The team built the computer chip with four tiny openings, which excrete droplets of chemicals using electro-osmosis—the movement of electrically charged particles in a fluid under the influence of an electric field.
Although the chip has many potential applications, the Stanford team is mainly concerned with devising a treatment for age-related macular degeneration, the most common cause of blindness.
Because the chip can draw droplets of fluid in as well as out, it could also enable researchers to take samples in real time, giving them a chemical picture of what goes on in living tissues during certain processes.
The chip could also serve as a drug delivery system, rationing small amounts of drugs precisely where they're needed, such as dopamine in the brains of people with Parkinson's disease.
However, the researchers say that it's still several years away from clinical trials.
"We still have to look at how these chips interact with the body and ensure there's no toxicity or clogging of microchannels and so forth," says Fishman. "There are a lot of potential pitfalls, as with any new technology, but the advantages are well worth the potential challenges."
The research is reported in the Proceedings of the National Academy of Sciences.
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