President Obama’s BRAIN initiative, which was launched back in April, may already have a new tool for mapping the human brain in its arsenal . Researchers at Duke University have used a carbon nanotube to capture electrical signals from individual neurons.
With a complete 3-D digital map of the human brain now available as part of the European Human Brain Project, brain research is gaining a lot of momentum. The carbon nanotube probe developed by the Duke team, which acts like a sort of harpoon, first spearing the neurons and then collecting the electrical signals they send to communicate with other neurons, is expected to provide a new level of insight into the human brain.
“To our knowledge, this is the first time scientists have used carbon nanotubes to record signals from individual neurons, what we call intracellular recordings, in brain slices or intact brains of vertebrates," said Bruce Donald, a professor of computer science and biochemistry at Duke University, in a press release.
The research (“Intracellular Neural Recording with Pure Carbon Nanotube Probes”), which was published in the journal PLoS ONE, overcame the shortcomings (literally) of other attempts to use carbon nanotubes (CNTs) as neuron probes. Previously, CNTs have proven to be too short or too thick for the job. But the Duke team was able to make their CNT probe one millimeter long (quite long for CNTs) and capable of monitoring the electrical signals between neurons more precisely than the glass or metallic electrodes that are typically used.
The researchers were able to achieve these unique CNT characteristics with a specially devised technique. They accumulated carbon nanotubes at the tip of a tungsten wire until the tubes took the shape of a needle-like probe. Next, they coated the probe with an insulating material and then removed the insulating material with a focused ion beam. This process of applying, then removing the insulating material gave the probe an extremely fine point.
"The results are a good proof of principle that carbon nanotubes could be used for studying signals from individual nerve cells," said Duke neurobiologist Richard Mooney, a study co-author, in press release. "If the technology continues to develop, it could be quite helpful for studying the brain."
While the researchers concede that more research needs to be done to improve the electrical recording capabilities of the probes—even as improvements are made to their geometry and the insulating layers—the Duke team has applied for a patent on the probe. The researchers expect that the technology could not only prove useful for mapping the brain but for creating brain-computer interfaces.
Photo: Inho Yoon and Bruce Donald, Duke
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.