Researchers have found that a hard probe inserted in the cerebral cortex of a rat model turns nearly as flexible as the surrounding gray matter in minutes, and induces less of the tough scarring that blocks hard probes that do not change.

The findings provided insights into the brain's responses to the mechanical mismatch between tissue and probe, researchers at Case Western Reserve University said.

Brain probes are used to study and treat neurological disorders. But, wires or silicon materials being used damage surrounding tissues over time and accumulate scarring, because they are far harder than brain matter.

In 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.

In 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 the experiment.

The 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 might improve our interaction with our brain, Tyler said.

Researchers linked short polymer chains together in a network mesh to make the material rigid to facilitate 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 tissues over time.

Four weeks after implantation, the density of neuronal nuclei adjacent to the new probe was significantly higher than surrounding the traditional probe. At eight weeks, the density of nuclei had increased around the wire probe to equal the density around the flexible probe, which remained unchanged.

But, 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.

The researchers are now comparing the impacts of the two probes at longer time intervals and testing for more indicators of the immune response.