Neurons find nanotubes stimulating

Thin films of carbon nanotubes deposited on transparent plastic can serve as a surface on which cells can grow. Researchers at the University of Texas Medical Branch at Galveston (UTMB) and Rice University suggest these nanotube films could potentially serve as an electrical interface between living tissue and prosthetic devices or biomedical instruments.

“As far as I know, we’re the first group to show that you can have some kind of electrical communication between these two things, by stimulating cells through our transparent conductive layer,” said Todd Pappas, director of sensory and molecular neuroengineering at UTMB’s Center for Biomedical Engineering and one of the study’s senior authors.

Pappas’ group employed two different types of cells in their experiments, neuroblastoma cells commonly used in test-tube experiments and neurons cultured from experimental rats. Both cell types were placed on ten-layer-thick “mats” of single-walled carbon nanotubes (SWNTs) deposited on transparent plastic. This enabled the researchers to use a microscope to position a tiny electrode next to individual cells and record their responses to electrical pulses transmitted through the SWNTs.

In addition to their electrical stimulation experiments, the scientists also studied how different kinds of SWNTs affected the growth and development of neuroblastoma cells. They compared cells placed on mats made of “functionalised” SWNTs - carbon nanotubes with additional molecules attached to their surfaces that may be used to guide cell growth or customise nanotube electrical properties - to cells cultured on unmodified “native” carbon nanotubes and conventional tissue culture plastic.

“Native carbon nanotubes support neuron attachment and growth well, as we expected, better than the two types of functionalised nanotubes we tested,” Pappas said. “Next we want to find a way to functionalise the nanotubes to make neuron attachment and communication better and make these surfaces more biocompatible.”

Another avenue Pappas wants to explore is finding out whether nanotubes are sensitive enough to record ongoing electrical activity in cells. “Where we want to get to is a device that can both sense and deliver stimuli to cells for things like prosthetic control,” Pappas said. “I think it’s definitely doable, and we’re pursuing that with Jim Tour (director of the Carbon Nanotechnology Laboratory at Rice) and his group. It’s great to be able to work with a guy who’s on the cutting edge of nanoelectronics technology. He seems to develop something new every week, and it’s really become a great interaction.”