Researchers based at the Laboratory of Advanced Materials, located at the Department of Ophthalmology, Fudan University, Shanghai, have reported the restoration of visual function in animal models of retinal degeneration using gold plated titanium oxide nanowires. The Au-TiO2 nanowire array, developed by the Chinese research team, was shown to absorb light in the visible range with a peak at 550nm. A series of ex vivo and in vivo experiments demonstrated electrical activity downstream of the nanowire arrays, together with brain activity in response to light stimulation in retinal degenerative mice models. The research group are now advancing the technology further to investigate colour discrimination with nanowires of different wavelength sensitivities.
Retinal prostheses may be the only option to potentially rescue or restore vision in patients in which most, if not all, the primary photoreceptors are lost. Significant research has been conducted in the field of retinal prostheses over the last two decades with advances been made by multiple research groups worldwide. Despite such, limitations in materials, microelectronic processing and signal transduction persist, with current technologies undergoing continuous iteration to improve patient outcomes. The current research aimed to develop artificial photoreceptors based on gold nanoparticle-decorated titania nanowire arrays to restore visual function in blind animal models with significantly degenerated photoreceptor cell populations. In in vivo experiments, animals were implanted with nanowire arrays over an area of approximately 0.5mm2–1.5mm2. The arrays were in contact with the inner nuclear layer and retinal ganglion cell (RGC) activities could be recorded using patch clamp pipettes.
Following implantation, the researchers were able to show that oriented semiconductor nanowire arrays were capable of generating photocurrent in response to light illumination and were capable of causing neuron depolarization, showing real-time transduction of photo-coded information. Data collected demonstrated light-evoked activities in the primary visual cortex in vivo, in addition to improved pupillary light reflex in conscious animals confirming the recovery of visual function 4–8 weeks after implant surgery. Taken together, the results suggest that such devices may be capable of adaption and use as retinal prostheses in humans. Not content with the development of an artificial layer of Au-TiO2 nanowires capable of restoring basic vision, the Fudan University researchers are already advancing the technology to investigate if colour discrimination might be possible using nanowires of different sensitivities. In concluding their study, the research group claimed that their artificial array, “absorbs light and generates photovoltage, and consequently triggers spiking activities in the interfaced neurons and restore light responses in the photoreceptor-degenerated retina. The spatial resolution is approaching or comparable to ~50 μm, and the size of receptive field is comparable to that in wild-type mice.”