Courtesy of Stanford University Medical Center
Using live cells arrayed on a chip, a Stanford University team has prototyped an implantable silicon wafer designed not only to improve sight in macular degeneration patients, but also to dispense drugs and collect fluid samples inside the body.1 The implant, now in development, will be nearly 2.5 cm in diameter, 10 microns thick, and honeycombed with hundreds of microchannels, which will dispense neurotransmitters either from onboard stores or a tiny reservoir implanted nearby.
Implanted in the macula, the part of the retina directly behind the pupil, the chip will be photoactivated: Light striking the chip creates an electric field that moves the transmitters (which will replace those the dead or dormant macular cells cannot provide) through the channels and out tiny apertures. The light's intensity will control dosage.
The same chip could both dispense drugs in the brain or elsewhere in the body and reabsorb those drugs if concentrations become too high. The chip can also sample biochemicals in situ and perhaps report its findings via a tiny radio transmitter.
Clinical trials are far off. The bulky prototype sports only four microchannels, and animal testing, detailed engineering, and miniaturization remain to be done. Still, says team leader Harvey Fishman, director of the Stanford Ophthalmic Tissue Engineering Laboratory at the university's medical school, "We've shown that this approach works."
- Bennett Daviss