Carbon nanotube-semiconductor nanocrystals film for light stimulation of the retina. Absorption of light by semiconductor nanorods attached to carbon nanotube film (upper right) results in retina stimulation (upper left).
The retina is a thin layer of tissue at the inner surface of the eye. Composed of light-sensitive nerve cells, it converts images to electrical impulses and sends them to the brain. Damage to the retina from macular degeneration, retinitis pigmentosa and other conditions can reduce vision or cause total blindness. In the United States alone, age-related macular degeneration (AMD) affects as many as 15 million Americans, with over 200,000 new cases diagnosed every year.
Scientists are currently designing a variety of medical devices to counter the effects of retinal disorders by sending visual signals to the brain. But these silicon-chip based solutions are typically hampered by their size, use of rigid parts, or requirement of external wiring such as to energy sources.
In the new study, Hebrew University researchers collaborated with colleagues from Tel Aviv University and Newcastle University to develop a novel approach for retina stimulation. Their device absorbs light and stimulates neurons without using wires or external power sources.
The Hebrew University researchers are Prof. Uri Banin, the Alfred & Erica Larisch Memorial Chair in Solar Energy, and his graduate student Nir Waiskopf, at the Institute of Chemistry and the Harvey M. Krueger Family Center for Nanoscience and Nanotechnology.
The researchers combined semiconductor nanorods and carbon nanotubes to create a wireless, light-sensitive, flexible implantable film. The film transforms visual cues to electric signals, mimicking the function of the photo-sensitive cells in the retina. Therefore, it could potentially form part of a future prosthetic device that will replace the damaged cells in the retina.
The researchers tested the new device on light-insensitive retinas from embryonic chicks and observed a neuronal response triggered by light.
According to the researchers, the new device is compact, capable of higher resolution than previous designs, and is also more effective at stimulating neurons. While much work remains until this can provide a practical solution, with additional research the researchers hope their carbon nanotube-semiconductor nanocrystals film will one day effectively replace damaged retinas in humans.
Prof. Uri Banin of the Hebrew University said: "This is a pioneering work demonstrating the use of highly tailored semiconductor nanocrystals in activation of biomedical functionalities. We hope this can lead to future implementation of this approach in retinal implants."
The researchers received funding from the Israel Ministry of Science and Technology, the European Research Council and the Biotechnology and Biological Sciences Research Council.