Carbon nanotubes may one day have the potential to perform repair of nerve tissue or deliver drugs directly to where the therapy is needed. The problem, though, is that it has been shown that carbon nanotubes interfere with neurons’ signaling pathways, effectively preventing their use in neural applications. Researchers from Brown University have now demonstrated that it’s actually the metal catalysts used in the production of the nanotubes that affect the critical ion channels.
Jakubek [Lorin Jakubek, a Ph.D. candidate in biomedical engineering –ed.] took single-walled carbon nanotubes to the laboratory of Diane Lipscombe, a Brown neuroscientist. The researchers zeroed in on ion channels located at the end of neurons’ axons. These channels are gateways of sorts, driven by changes in the voltage across neurons’ membranes. When an electrical signal, known as an action potential, is triggered in neurons, these ion channels “open,” each designed to take in a certain ion. One such ion channel passes only calcium, a protein that is critical for transmitter release and thus for neurons to communicate with each other.
In experiments using cloned calcium ion channels in embryonic kidney cells, the scientists discovered that nickel and yttrium, two metal catalysts used to form the single-walled carbon nanotubes, were interfering with the ion channel’s ability to absorb the calcium.
Because its ionic radius is nearly identical to calcium’s, yttrium in particular “gets stuck and prevents calcium from entering and passing through. It’s an ion pore blocker,” said Lipscombe, who specializes in neuronal ion channels and is a corresponding author on the paper.
The experiments showed that yttrium in trace amounts — less than 1 microgram per milliliter of water — may disrupt normal calcium signaling in neurons and other electrically active cells, an amount far lower than what had been thought to be safe levels. With nickel, the amount needed to impede calcium signaling was 300 times higher.
Press release: Researchers Pinpoint Neural Nanoblockers in Carbon Nanotubes …
Image: Metal catalysts – nickel and particularly yttrium – used to create carbon nanotubes can block a key signalling pathway in neurons. Experiments show the metal particles tend to plug cellular pores normally reserved for calcium ions.