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Developing Artificial Retina: Electric Link Between Neurons, Light-Sensitive Nanoparticle Films Created
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 (UTMB) and the University of Michigan. 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.
Nanoparticles are artificially created bits of matter not much bigger than individual atoms. Their behavior is controlled by the same forces that shape molecules; they also exhibit the bizarre effects associated with quantum mechanics. Scientists can exploit these characteristics to custom-build new materials "from the bottom up" with characteristics such as compatibility with living cells and the ability to turn light into tiny electrical currents that can produce responses in nerves.
That's what the UTMB and Michigan researchers did, using a process devised by Michigan chemical engineering professor Nicholas Kotov, one of the authors of a paper on the research appearing in the current issue of Nano Letters. 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 the Nano Letters paper. "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."
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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 (UTMB) and the University of Michigan. 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.
Nanoparticles are artificially created bits of matter not much bigger than individual atoms. Their behavior is controlled by the same forces that shape molecules; they also exhibit the bizarre effects associated with quantum mechanics. Scientists can exploit these characteristics to custom-build new materials "from the bottom up" with characteristics such as compatibility with living cells and the ability to turn light into tiny electrical currents that can produce responses in nerves.
That's what the UTMB and Michigan researchers did, using a process devised by Michigan chemical engineering professor Nicholas Kotov, one of the authors of a paper on the research appearing in the current issue of Nano Letters. 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 the Nano Letters paper. "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."
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