"These astrocytes can't make scar tissue unless they can adhere to the probe," Webster said. "Fewer astrocytes adhering to the nanotubes means less scar tissue will be produced."
The Purdue researchers pressed numerous nanofibers together to form discs and placed them in petri plates. Then the petri plates were filled with a liquid suspension of astrocytes. After one hour the nanotube disks were washed and a microscope was used to count how many of the dyed astrocytes washed out of the suspension, which enabled the researchers to calculate how many astrocytes stuck to the nanotubes. About 400 astrocytes per square centimeter adhered to the nanotubes containing the small surface features, compared to about 800 for nanotubes not containing the small surface features. The researchers repeated the experiment while leaving the nanotubes in the cell suspension for two weeks, yielding similar results.
When the nanotubes were placed in a suspension with neurons, the brain cells sprouted about five neurites, compared with the usual three neurites formed in suspensions with nanotubes that didn't have the small surface features.
Researchers plan to make brain probes and implants out of a mixture of plastics and nanotubes. The findings demonstrated that progressively fewer astrocytes attached to this mixture as the concentration of nanotubes was increased and the concentration of plastics was decreased.
"That means if you increase the percentage of carbon nanofibers you can decrease the amount of scar tissue that might form around these electrodes," Webster said.
The nanometer-scale bumps mimic features found on the surface of a brain protein called laminin.
"Neurons recognize parts of that protein and latch onto it," Webster said.
The crucifix-shaped protein then helps neurons sprout neurites, while suppressing the formation of scar tissue
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Contact: Emil Venere
venere@purdue.edu
765-494-4709
Purdue University
7-Jan-2004