hard probe inserted in the cerebral cortex of a rat model turns nearly
as pliable as the surrounding gray matter in minutes, and induces less
of the tough scarring that walls off hard probes that do not change,
researchers at Case Western Reserve University have found.
the first test of the nanocomposite probe inspired by the dynamic skin
of the sea cucumber, the immune response differed compared to that of a
metal probe, and appeared to enable the brain to heal faster.
findings, which provide insights to the brain’s responses to the
mechanical mismatch between tissue and probe, are described in the
online edition of the Journal of Neural Engineering.
probes are used to study and treat neurological disorders. But, wires
or silicon materials being used damage surrounding tissue over time and
accumulate scarring, because they are far harder than brain matter.
this test, “The scar wall is more diffuse; the nanocomposite probe is
not completely isolated in the same way a traditional stiff probe is,”
said Dustin Tyler, a professor of biomedical engineering and leader of
result may prove beneficial. Studies by others in the field indicate
the greater the isolation, the less effective the probe is at recording
and relaying brain signals.
worked with James P. Harris, a graduate student in biomedical
engineering and the lead author on the paper; Biomedical Engineering
Professor Jeffery Capadona; Stuart J. Rowan, professor of macromolecular
science and engineering, and former graduate student Kadhiravan
Shanmuganathan; Robert H. Miller, professor of neurosciences at Case
Western Reserve School of Medicine; Christoph Weder, formerly a
professor of macromolecular science and engineering at Case Western
Reserve and now at the University of Fribourg; and Harvard Neurology
Professor and Research Fellow Brian C. Healy.
new probe material is inspired by the skin of the sea cucumber, which
is normally soft and flexible, but becomes rigid for its own defense
within seconds of being touched. These changing mechanical properties
may improve our interaction with our brain, Tyler said.
the nanocomposite, short polymer chains are linked together in a
network mesh to make the material rigid, which is necessary for
insertion into the cortex. In the presence of water, the mesh begin
unlinking in seconds, changing to a soft, rubbery material designed to
cause less damage to surrounding brain tissue over time.
test the effects of the changing mechanical properties, metal probes
were coated in a think layer of nanocomposite materal. When both were
implanted into the brain, the chemical properties as seen by the brain
were these same, but the mechanical properties were very different.
weeks after implantation, the density of neuronal nuclei adjacent to
the new probe was significantly higher than surrounding the traditional
eight weeks, the density of nuclei had increased around the wire probe
to equal the density around the flexible probe, which remained
hypothesis is that the soft material allows the brain to recover more
quickly,” Tyler said. “Both probes cause the same insult to the tissue
testing for scar components at 8 weeks showed that although the
thickness of scar surrounding the metal probe had shrunk, the scar was
denser and more complete than that around the nanocomposite probe. This
dense scar separated the stiff probe from the brain more than the loose
tissue around the more flexible probe.
researchers are now comparing the impacts of the two probes at longer
time intervals and testing for more indicators of the immune response,
“We’re trying to better understand the nuances regarding the response to the nanocomposite and how it would improve recordings.”
Mechanically adaptive intracortical implants improve the proximity of neuronal cell bodies