Graphene nanoribbons dissolved in the biocompatible polymer, polyethylene glycol (PEG), could be used to knit together damaged or even severed spinal cord tissue, thanks to research at Rice University in Texas, USA. Preliminary tests in animals with spinal injury are described in the journal Surgical Neurology International.
Graphene nanoribbons were customized for medical use by Rice's William Sikkema, who found that biocompatible nanoribbons with PEG-functionalized edges can form an electrically active network that helps the severed ends of a spinal cord reconnect. "Neurons grow nicely on graphene because it's a conductive surface and it stimulates neuronal growth," explains James Tour. Earlier research has already demonstrated that neurons can grow along a graphene surface.
"We're not the only lab that has demonstrated neurons growing on graphene in a Petri dish," Tour adds. "The difference is other labs are commonly experimenting with water-soluble graphene oxide, which is far less conductive than graphene, or non-ribbonized structures of graphene." Tour and his colleagues have developed a method to add polymer chains to graphene nanoribbons that then make it water soluble without disrupting their conductivity. "We're just now starting to see the potential for this in biomedical applications," Tour explains. He adds that ribbonized graphene structures allow for much smaller amounts to be used while preserving a conductive pathway that would ultimately allow bridging of a damaged spinal cord.
The team has demonstrated that their material could restore function in a rodent with a severed spinal cord in a procedure performed at Konkuk University in South Korea by co-authors Bae Hwan Lee and C-Yoon Kim. Tour adds that the material reliably allowed motor and sensory neuronal signals to cross the gap 24 hours after complete transection of the spinal cord. The rodent experienced almost complete recovery of motor control after two weeks. 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. "Our goal is to develop this as a way to address spinal cord injury. We think we're on the right path," he adds.
The neurophysiological signs are promising but there now needs to be an analysis of behavior and movement following repair of complete severance. Moreover, tests now need to be carried out in a statistically significant fashion by the behavioral analysis group. The next step will be to see how well the neurophysiological markers of recovery correlate with positive behavioral and locomotive changes. Details of the work are reported in the journal Surgical Neurology International [JM Tour et al., Surg. Neurol. Int. (2016) 7(25), 632 DOI: 10.4103/2152-7806.190475]
David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".