Implantable fibres have been an enormous boon to brain research, allowing scientists to stimulate specific targets in the brain and monitor electrical responses. But similar studies in the nerves of the spinal cord, which might ultimately lead to treatments to alleviate spinal cord injuries, have been more difficult to carry out. That’s because the spine flexes and stretches as the body moves, and the relatively stiff, brittle fibres used today could damage the delicate spinal cord tissue.
Now, researchers at the Massachusetts Institute of Technology have developed a rubber-like fibre that can flex and stretch while simultaneously delivering both optical impulses, for optoelectronic stimulation, and electrical connections, for stimulation and monitoring.
The new fibres are described in the journal Science Advances, by MIT graduate students Chi Lu and Seongjun Park, Professor Polina Anikeeva, and eight others at MIT, the University of Washington, and Oxford University.
“The goal was to mimic the stretchiness and softness and flexibility of the spinal cord,” said Anikeeva. “You can match the stretchiness with a rubber. But drawing rubber is difficult — most of them just melt.
“Eventually, we’d like to be able to use something like this to combat spinal cord injury. But first, we have to have biocompatibility and to be able to withstand the stresses in the spinal cord without causing any damage,” she says.
The team combined a newly developed transparent elastomer, which could act as a waveguide for optical signals, and a coating formed of a mesh of silver nanowires, producing a conductive layer for the electrical signals. To process the transparent elastomer, the material was embedded in a polymer cladding that enabled it to be drawn into a fiber that proved to be highly stretchable as well as flexible, Lu says. The cladding is dissolved away after the drawing process.
After the entire fabrication process, what’s left is the transparent fibre with electrically conductive, stretchy nanowire coatings. “It’s really just a piece of rubber, but conductive,” Anikeeva says. The fibre can stretch by at least 20 to 30 per cent without affecting its properties, she says.
The fibres are not only stretchable but also very flexible. “They’re so floppy, you could use them to do sutures and deliver light at the same time,” she says.
“We’re the first to develop something that enables simultaneous electrical recording and optical stimulation in the spinal cords of freely moving mice,” Lu says. “So we hope our work opens up new avenues for neuroscience research.”
Image credit: Chi (Alice) Lu and Seongjiun Park, MIT
Source: MIT News
