By Simon Makin March 1, 2016
New implants made of fine, flexible mesh last longer and cause less damage than current ones do
Brain
implants have been around for decades—stimulating motor areas to alleviate
Parkinson's disease symptoms, for example—but until now they have all
suffered from the same limitation: because brains move slightly during
physical
activity and as we breathe and our heart beats, rigid implants rub and damage
tissue. This means that eventually, because of both movement and scar-tissue
formation, they lose contact with the cells they were monitoring.
Now a
group of researchers, led by chemist Charles Lieber of Harvard University, has
overcome these problems using a fine, flexible mesh. In 2012 the team showed
that cells could be grown around such a mesh, but that left the problem of how
to get one inside a living brain. The solution the scientists devised was to
draw the mesh—measuring a few millimeters wide—into a syringe, so it would roll
up like a scroll inside the 100-micron-wide needle, and inject it through a
hole in the skull.
In a
study published in Nature Nanotechnology last year, the team
injected meshes studded with 16 electrodes into two brain regions in mice. The
mesh is composed of extremely thin, nanoscale polymer threads, sparsely
distributed so that 95 percent of it is empty space. It has a level of
flexibility similar to brain tissue. “You're starting to make this nonliving
system look like the biological system you're trying to probe,” Lieber
explains. “That's been the goal of my group's work, to blur the distinction
between electronics as we know it and the computer inside our heads.”
Once
inside, the mesh unfurls—either enough to meet the sides of brain cavities
called ventricles or very slightly if injected into solid tissue—to form a
three-dimensional structure. The researchers showed that the implants
integrated with tissue to form stable connections, with no inflammation five
weeks later. “It's the dawn of biointegration,” says Ivan Minev of the Center
for Neuroprosthetics at the Swiss Federal Institute of Technology in Lausanne, who
was not involved in the work.
The
researchers claim the mesh can be positioned with an accuracy approaching the
scale of individual neurons. Activity can then be recorded to study the
workings of brain circuitry, or neurons can be stimulated for therapeutic
applications such as the deep-brain stimulation used to treat Parkinson's
disease. One application Lieber envisions is injecting implants into the brains
of stroke victims alongside neural stem cells to study how the stem cells grow
and alter neural circuitry during recovery. “This opens up unprecedented
opportunities, both for fundamental brain science and for any therapeutic
applications where you need stability beyond a very short time,” Lieber says.
He believes the device could “completely change the picture of what's possible
with electrical brain interfaces.
No comments:
Post a Comment