and such technology, researchers need
some new tools. For one thing, they
might need a better way to develop the
interface between an array of sensors
inside the eye and the functioning cells
of the retina or optic nerve.
At the Italian Institute of Technology
in Genova, Italy, Guglielmo Lanzani,
Fabio Benfenati and their teams are
working on a new approach to building
an interface between electronics and
biology. In the January 17, 2011, online
edition of Nature Communications, Lanzani and his colleagues described their
work with an organic polymer.
Maria Rosa Antognazza, a postdoctoral researcher in Lanzani’s laboratory,
points out that some “existing artificial-retina prostheses are based on silicon,
and one of the major challenges is the
biocompatibility of the electrodes and
long-term durability.” ;e electrode
array in the Argus device, however, is
also polymer-based.
Although Lanzani and Benfenati’s
group is not even close to testing its
technology on humans, they are developing a new way to connect electronics to the nervous system. ;ey grew
primary neurons, which were taken
from a rat’s brain, on an optoelectronic
polymer composed of regio-regular
poly(3-hexylthiophene- 2,5-diyl) with
phenyl-C61-butyric-acid-methyl ester
(rr-P3HT:PCBM). Presumably, such an
organic substrate—the polymer—would
be more biocompatible than silicon.
“;ese are known as synthetic polymers
because they are synthesized in the lab,”
says Antognazza, “but the molecular
structures share some properties with
natural structures found in living
tissues.” She adds that the softness of
this polymer could be advantageous.
“Neurons, as well as each living system,
prefer to adhere to a soft substrate, like a
polymer,” says Antognazza. In fact, she
says that the rat-brain neurons formed
good adhesion with the polymer.
Eventually, the idea will be to attach
such a photosensitive polymer to the
retina. First, though, this research team
needed to validate a far simpler step. As
Antognazza explains, “We wanted to see
A team of researchers at the Italian
Institute of Technology is working on a
polymer-based interface that could one
day connect electronics to vision cells.
This image shows neurons cultured on
top of the polymer.
Courtesy of Maria Rosa Antognazza
[ Growing retinal cells ]
In the future, researchers may grow arti-;cial retinas from stem cells. This image
shows a 24-day-old retina cultured from
stem cells.
Courtesy of Mototsugu Eiraku
if an electrical signal from the polymer
could stimulate neuronal activity.”
Once they had a layer of primary
neurons living on the polymer, they
illuminated it. ;e light generated electri-
cal currents in the optoelectronic polymer,
and those electrical charges stimulated
the neurons. In fact, the light-stimulated
polymer spawned neuronal action poten-
tials, which are the units of information
carried in the nervous system.
Despite this initial success, this
research team faces many more hurdles.
;ey are already testing the biocompatibility of the polymer. ;ey also want
to see if the light-activated polymer can
stimulate cells in a real retina—starting
with one removed from an animal.
Rebuilding what’s broken
Instead of bypassing a damaged retina,
clinicians might one day—probably
decades from now—simply grow a new
one from other cells. In Kobe, Japan,
work by Mototsugu Eiraku of the
RIKEN organogenesis and neurogen-
esis group aims at developing such an
approach. Using stem cells that would
lead to the retina in a mouse, Eiraku
created what he calls an optic cup, basi-
cally the start of developing a biological
retina. He believes that stem cells could
be used to generate a complete retina.
Mike May ( mike@techtyper.com) is a freelance
writer and editor who specializes in science and
technology. His work has appeared in BioOptics
World, Nature, Nature Medicine, Science,
Scientific American and other publications.
