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Spectrum: Autism Research News

Injected into the brain, silicon net slyly spies on neurons

by  /  27 September 2016
THIS ARTICLE IS MORE THAN FIVE YEARS OLD

This article is more than five years old. Autism research — and science in general — is constantly evolving, so older articles may contain information or theories that have been reevaluated since their original publication date.

Editor’s Note

This article was originally published 1 July 2015 based on a study published 8 June 2015 in Nanotechnology1. We have updated the article following publication of a second study published 29 August in Nature Methods2. Updates appear below in brackets.

Slip in: A syringe injects an electronic mesh for recording neuron activity through a small hole in a mouse’s skull.

A new injectable electronic mesh enables researchers to gently eavesdrop on the chatter of hundreds of neurons inside the brain, according to a paper published 8 June in Nature Nanotechnology1.

The flexible scaffold is made of ultrafine silicon wires encased in a polymer insulator. The wires carry embedded metal sensors that pick up neuronal impulses, which may be disrupted in people with autism.

Beyond monitoring neurons, the mesh probe could eventually be used to deliver “appropriate feedback stimulation to improve autism symptoms,” says one of its developers, Charles M. Lieber, professor of chemistry at Harvard University.

Unlike other flexible arrays, this one rolls up to fit through a needle the width of a human hair. As a result, researchers can simply inject it into the brain rather than performing delicate brain surgery.

Once inside the brain, the mesh gently unfolds to a rectangle about 2 millimeters wide and 4 centimeters long that conforms to the brain’s nooks and wrinkles. It connects to recording electronics outside the skull.

Living cells grow in and around the open spaces in the device. The intermingling of tissue and electronics is critical for producing high-quality recordings.

The clean integration of the mesh with brain tissue also [means] that the device can remain in working order inside the brain for months or [potentially] years, the researchers say. Rigid conventional arrays can damage the surrounding tissue, eroding the accuracy of their recordings.

To test the device, the researchers injected it into synthetic polymers that mimic delicate brain tissue. The mesh unfurled inside the specially designed cavities without damaging itself or the polymer walls surrounding it.

The research team next injected the mesh into two brain regions of living mice — the large open space called the lateral ventricle and the hippocampus, a curved structure tucked deep in the brain. The scaffold expanded from its rolled-up state to about 80 percent of its total area within these brain regions in less than an hour. Tests of the array’s recording capability show that it can detect the signals given off by individual neurons in a manner comparable to other thin electronics.

[In a subsequent study, published 29 August in Nature Methods, the researchers injected a mesh with 16 recording electrodes into the brains of young adult mice2. They tracked the activity of the same neurons for up to eight months, revealing changes in neuron firing that occur as the mice age. More rigid electrode arrays tend to detach from neurons within weeks.]

[In the future,] the team plans to inject the array into the brains of baby mice, where its flexibility should allow it to move as the mice grow and record changes in brain signaling over [developmental] time. Creating larger arrays with more sensors will give the device the ability to record thousands of neurons, the researchers say.

 


References:
  1. Liu J. et al. Nat. Nanotechnol. 10, 629-636 (2015) PubMed
  2. Fu T.M. et al. Nat. Methods Epub ahead of print (2016) PubMed