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Nicole Wagner, Jordan Greco, Robert Birge; Protein-Based Retinal Implant. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1384.
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To develop a protein-based retinal implant to restore vision for the millions of patients suffering from age-related macular degeneration (AMD) and retinitis pigmentosa (RP).
A flexible implant, consisting of multiple, oriented layers of bacteriorhodopsin (BR) on an ion-permeable, biologically inert substrate is generated by using electrostatic layer-by-layer adsorption. Bacteriorhodopsin, a highly stable, light-activated proton pump, generates a unidirectional proton gradient in response to incident light. This proton gradient activates acid-sensing ion channels (ASICs) on the bipolar and ganglion cells of the retina. The resulting implant was tested for the ability to stimulate the ganglion cells of P23H rat retinas ex vivo using extracellular recording.
Studies using extracellular recording of retinal ganglion cells in excised P23H rat retinas show that pumping protons in the direction of the ganglion and bipolar cell milieu generates a neural response. Moreover, the activation efficiency, or ability to induce a neural response in P23H rat retinas ex vivo, correlates directly with the intensity of incident red light (~640 nm). Importantly, the light intensity required to induce a neural response is comparable to that of ambient light, a capability critical to the function of the implant in humans.
The preliminary results demonstrate the potential efficacy of BR as the photoactive medium in a protein-based retinal implant for the treatment of AMD and RP.
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