"Previous studies have looked at the behavior of carbon nanotubes on neurons. However, the impurity in the nanotubes significantly affected the results. After we developed pure few-walled carbon nanotubes in our lab, we discovered that nanotubes actually accelerated the growth of the neuronal cells significantly," said Liu.
Neural circuits can be corrupted by elevated chloride within neurons. A number of diseases involve such neural circuit damage, including chronic pain, epilepsy, and traumatic brain injury.
Low levels of chloride within neurons are maintained by a chloride transporter protein called KCC2, which functions by churning chloride ions out of the cell. In mature neurons, there is no back-up for this function.
The immature neurons cultured in Liedtke's laboratory had high levels of chloride, but as the cells matured, their chloride levels dropped as KCC2 increased. When the neurons were exposed to carbon nanotubes, the cells matured much faster, and the chloride levels dropped more quickly. Researchers learned that younger cells exposed to carbon nanotubes produced more KCC2 protein.
"Carbon nanotubes enhanced the regulation of chloride in neurons to normal levels. These changes are of enormous significance to the cell," Liedtke said.
The increase in KCC2 protein was also connected to a rise in calcium in the neurons. The increased calcium levels activated a protein found in the brain called CaMKII which signals a neuron to make more KCC2.
Similar results were observed in mice brains, as the carbon nanotubes prompted an increase in activity of the KCC2 gene, suggesting that the few-walled carbon nanotubes
|Contact: Rachel Bloch Harrison|
Duke University Medical Center