‘Knit’ severed spinal cords with graphene ribbons

A new material made of graphene nanoribbons and a common polymer might help knit damaged or even severed spinal cords.

The nanoribbons are highly soluble in polyethylene glycol (PEG), a biocompatible polymer gel used in surgeries, pharmaceutical products, and in other biological applications. When the nanoribbons have their edges functionalized with PEG chains and are then further mixed with PEG, they form an electrically active network that helps the severed ends of a spinal cord reconnect.

“Our goal is to develop this as a way to address spinal cord injury. We think we’re on the right path.”

“Neurons grow nicely on graphene because it’s a conductive surface and it stimulates neuronal growth,” says James Tour, a chemist at Rice University.

Earlier experiments have suggested that neurons will grow along graphene.

“We’re not the only lab that has demonstrated neurons growing on graphene in a petri dish,” he says. “The difference is other labs are commonly experimenting with water-soluble graphene oxide, which is far less conductive than graphene, or nonribbonized structures of graphene.

“We’ve developed a way to add water-solubilizing polymer chains to the edges of our nanoribbons that preserves their conductivity while rendering them soluble, and we’re just now starting to see the potential for this in biomedical applications,” Tour says.

illustration of how Texas-PEG is made
Researchers insert potassium atom between layers of multiwalled carbon nanotubes to split them into graphene nanoribbons. Next they add ethylene oxide (not shown) to render the edges with solubilizing polyethylene glycol addends. This leaves the flat surfaces of electrically conductive graphene nanoribbons intact to give a conductive surface for neuron growth between the two ends of a severed spinal cord. (Credit: Tour Group/Rice)

Ribbonized graphene structures allow for much smaller amounts to be used while preserving a conductive pathway that bridges the damaged spinal cords. Tour says only 1 percent of the material, dubbed Texas-PEG, consists of nanoribbons, but that’s enough to form a conductive scaffold through which the spinal cord can reconnect.

Successful repair in a rodent

Texas-PEG succeeded in restoring function in a rodent with a severed spinal cord in a procedure performed at Konkuk University in South Korea by coauthors Bae Hwan Lee and C-Yoon Kim.

Tour says the material reliably allowed motor and sensory neuronal signals to cross the gap 24 hours after complete transection of the spinal cord and almost perfect motor control recovery after two weeks. The results appear in the journal Surgical Neurology International.

“This is a major advance over previous work with PEG alone, which gave no recovery of sensory neuronal signals over the same period of time and only 10 percent motor control over four weeks,” Tour says.

Tour says Texas-PEG’s potential to help patients with spinal cord injuries is too promising to be minimized.

“Our goal is to develop this as a way to address spinal cord injury. We think we’re on the right path,” he adds.

Source: Rice University

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Source: Futurity