The results have recently been published in the prestigious scientific journal Advanced Materials.
Photoactive materialThe retina consists of several thin layers of cells. Light-sensitive neurons in the back of the eye convert incident light to electric signals, while other cells process the nerve An array of semitransparent organic pixels on top of a ultrathin sheet of gold. The thickness of both the organic islands and the underlying gold is more than one-hundred times thinner than a single neuron. Photo credit: Thor Balkhedimpulses and transmit them onwards along the optic nerve to an area of the brain known as the “visual cortex”. An artificial retina may be surgically implanted into the eye if a person’s sight has been lost as a consequence of the light-sensitive cells becoming degraded, thus failing to convert light into electric pulses.
The artificial retina consists of a thin circular film of photoactive material, and is similar to an individual pixel in a digital camera sensor. Each pixel is truly microscopic – it is about 100 times thinner than a single cell and has a diameter smaller than the diameter of a human hair. It consists of a pigment of semi-conducting nanocrystals. Such pigments are cheap and non-toxic, and are commonly used in commercial cosmetics and tattooing ink.
“We have optimised the photoactive film for near-infrared light, since biological tissues, such as bone, blood and skin, are most transparent at these wavelengths. This raises the possibility of other applications in humans in the future,” says Eric Glowacki.
Microscopic donutHe describes the artificial retina as a microscopic doughnut, with the crystal-containing pigment in the middle and a tiny metal ring around it. It acts without any external connectors, and the nerve cells are activated without a delay.
“The response time must be short if we are to gain control of the stimulation of nerve cells,” says David Rand, postdoctoral researcher at Tel Aviv University. “Here, the nerve cells are activated directly. We have shown that our device can be used to stimulate not only neurons in the brain but also neurons in non-functioning retinas.”
Eric Glowacki and his research group work at the Laboratory of Organic Electronics in Norrkoping, Sweden. The research group is part of a larger research initiative called the Wallenberg Center for Molecular Medicine, WCMM, at Linköping University. This initiative has created the unique environment necessary to develop this technology in a collaboration between nanomaterials scientists, biomedical engineers, and biologists.
Direct electrical neurostimulation with organic pigment photocapacitors, David Rand, Marie Jakesova, Gur Lubin, Ieva Vebraite, Moshe David Pur, Vedran Derek, Tobias Cramer, Serdar Sariciftci, Yael Hanein, Eric Daniel Glowacki, Advanced Materials 2018. DOI: 10.1002 adma.201707292R1
Translation: George Farrants