Scanning electron micrograph detailing the structure of the carbon nanotube sponge, single cells are visible invading the artificial skeleton.
Scanning electron microscopy imaging of the tight interactions between the carbon nanotube 3D sponge and the living brain tissue (implant picture taken after 2 weeks in vivo).A sponge-like structure made from carbon nanotubes could be the ideal scaffold to help damaged neural tissue regenerate, according to researchers [Usmani et al., Sci. Adv. 2 (2016) e1600087].
The team from the International School for Advanced Studies (SISSA/ISAS) in Trieste, together with colleagues from the University of Trieste, ELETTRA Synchrotron Light Source, the University of Rome Tor Vergata, CIC biomaGUNE in San Sebastian and Ikerbasque in Bilbao created a three-dimensional mesh from interconnected multiwalled carbon nanotubes.
When spinal cord tissue is introduced into the scaffold, the carbon nanotubes guide the formation of nerve fibers. Crucially, the nerve fibers intertwine with the carbon nanotubes creating a hybrid structure.
“The nerves integrate perfectly with the carbon nanotube scaffold, leading to a very promising hybrid,” explains Maurizio Prato of the University of Trieste, CIC biomaGUNE and Ikerbasque.
Without a scaffold, nerve fibers regrow in all directions – not necessarily bridging a gap between damaged sections. But when a piece of the carbon nanotube sponge is inserted into the space between the two segments of severed spinal tissue, the situation is completely different. The nerve fiber-carbon nanotube mesh hybrid material directs the cells to reconnect separated segments of spinal tissue.
“We show... the spontaneous formation of webs of nerve fibers invading and following the nanotube structure,” says Prato.
But a simple physical connection is not enough – there must also be a functional connection between the two groups of neurons so that signals can be passed along.
“With signal analysis techniques, we demonstrate that spontaneous nervous activity in the two samples [is] correlated, indicating a connection, and by applying an electrical signal to one sample, activity of the second sample can be triggered – but only when the nanotubes are present,” explains colleague David Zoccolan.
The team also tested how the body’s immune system reacts to the carbon nanotube scaffold by implanting samples of the pure material into rats’ brains. After an initial inflammatory response, there was no sign of further adverse tissue reactions. But better than that,the researchers found neurons inside the implanted scaffold indicating that the approach is promising for central nervous system repair and regeneration.
“We show a perfect integration of nerve tissues with an artificial scaffold,” says Prato. “The compatibility of this new material is impressive and could lead to alternative solutions to still unsolved problems.”
Those problems could include the treatment of movement disorders like Parkinson’s, where implanted electrodes stimulate neural tissue to recover or rehabilitate lost function. The new carbon nanotube mesh could be used to coat these electrodes to encourage their acceptance by the body.
This article was originally published in Nano Today (2016), doi:10.1016/j.nantod.2016.08.004