Spinach offers hope for AMD sufferers

Spinach may help restore sight in people who are legally blind, US researchers reveal this week. Scientists at the Department of Energy's Oak Ridge National Laboratory at the University of Southern California are investigating whether a protein from spinach could replace a non-functioning light receptor in the eye. Progress in this field could lead to hope for people suffering from age-related macular degeneration or retinitis pigmentosa, diseases that are leading causes of blindness worldwide. "Although the neural wiring from the eye to the brain is intact in people with these diseases, their eyes lack photoreceptor activity,"​said Eli Greenbaum of ORNL's Chemical Technology Division in a statement. Greenbaum and colleagues propose replacing these non-functioning photoreceptors with a spinach protein that gives off a small electrical voltage after capturing the energy of incoming photons. The main function of Photosystem I, a photosynthetic reaction center protein, is to perform photosynthesis in leaves using the energy of the sun to make plant tissue. Greenbaum's collaborator, Mark Humayun, a professor in the University of Southern California's Doheny Eye Institute and his research team showed that if retinal tissue is stimulated electrically using pinhead-sized electrodes implanted in the eyes of legally blind patients, many can see image patterns that mimic the effects of stimulation by light. Greenbaum believes that it might be possible to use Photosystem I protein to restore photoreceptor activity. Experiments by Greenbaum's team showed that Photosystem I protein can capture photon energy and generate electric voltages of up to 1 volt. "What we need to find out is whether these voltages can trigger neural events and allow the brain to interpret the images,"​ Greenbaum said. In recent research, the team showed that Photosystem I reaction centres protein could be incorporated into the membrane of an artificial liposome, a tiny spherical particle formed by a fatty (lipid) membrane enclosing a watery compartment. The artificial membrane mimics that of a living cell. Greenbaum's team also showed that the Photosystem I reaction centers can work inside a liposome, which means it produces the experimental equivalent of a voltage when it comes into contact with light. A liposome will likely be used to deliver Photosystem I reaction centres protein to a retinal cell.