Research could lead to artificial retinas

February 5, 2008, Galveston, TX--The world's first direct electrical link between nerve cells and photovoltaic nanoparticle films has been achieved by researchers at the University of Texas Medical Branch at Galveston and the University of Michigan, according to a story in the Galveston County Daily News.

The development opens the door to applying the unique properties of nanoparticles to a wide variety of light-stimulated nerve-signaling devices--including the possible development of a nanoparticle-based artificial retina.

The process starts with a glass plate and then builds a layer-by-layer sandwich of two kinds of ultra-thin films, one made of mercury-tellurium nanoparticles and another of a positively charged polymer called PDDA. The scientists then added a layer of ordinary clay and a cell-friendly coating of amino acid, and placed cultured neurons on the very top. When light shines on them, the mercury-tellurium nanoparticle film layers produce electrons, which then move up into the PDDA film layers and produce an upward-moving electrical current.

"As you build up the layers of this, you get better capabilities to absorb photons and generate voltage," said UTMB research scientist Todd Pappas, lead author on a recent Nano Letters paper on the subject. "When the current reaches the neuron membrane, it depolarizes the cell to the point where it fires, and you get a signal in the nerve."

Although light signals have previously been transmitted to nerve cells using silicon (whose ability to turn light into electricity is employed in solar cells and in the imaging sensors of video cameras), nanoengineered materials promise far greater efficiency and versatility.

For more information, visit www.utmb.edu.