Comparing a single wall carbon nanotube composite substrate to poly-L-ornithine

Many modern neurological diseases are treated through implanted electrodes in the brain. While this is a huge advance from no implant at all, there is a large amount of interface between brain tissue and the electrode, often leading to scarring around the electrode that reduces performance and longevity.

One possible solution to this quandary is to use single carbon wall nanotubes (SWNTs) in place of the larger electrodes. The advantages of this material are multifold: they are durable and modifiable, but still are biocompatible and still conduct electricity.

In the current study, the authors attempted to determine whether the SWNTs could recruit and interact with neural stem cells. As opposed to terminally differentiated cells, the stem cells would be able to remodel themselves and interface with the implant, which would reduce scarring of neural tissue.

To investigate whether SWNT material is biocompatible enough to support the differentiation of stem cells, Jan et al. used a layer-by-layer technique to test the differentiation of mouse cortical neural stem cells on a SWNT composite film. Using scanning electron microscopy, they compared the differentiation of neurospheres on the SWNT composite material with the neurospheres on poly-L-ornithine (PLO), a standard culture used in neural stem cell studies. The amount of differentiation in these two substrates was about the same, with highly branched processes developing in both substrates.

After immunostaining, it was determined that the SWNT composite substrate led to the formation of more neurons and oligodendrocytes, while the PLO substrate led to the formation of more astrocytes, although the differences were just barely statistically significant. The authors conclude that the layer-by-layer SWNT composite film leads to just as much cell viability as the standard PLO substrate, which suggests some exciting potential applications in neural nanomedicine.

Reference

Edward J, Kotov NA. 2007 Succesful differentiation of mouse neural stem cells on layer-by-layer assembled single-walled carbon nanotube composite. Nano Letters 7: 1123-1128. doi: 10.1021/nl0620132.