Invited Speaker

Carbon Nanotubes as Modulators of Neuronal Growth
Vladimir Parpura
USA

We are attempting to define whether carbon nanotubes (CNTs) could be used as prosthetics devices in the process of neuronal regeneration after injury. Towards that end we are investigating neuronal growth on multi-walled CNTs (MWNTs). Neuronal growth was systematically controlled by modified MWNTs, prepared by covalently conjugating CNTs with functionalities designed to carry negative, zwitterionic or positive charges at physiological extracellular pH. By using these CNTs as the scaffold for neuronal growth, it was found that the neurons grown on positively charged MWNTs showed more numerous growth cones, longer neurite outgrowth and more successful neurite branching than the neurons grown on negatively charged CNTs.

Similarly, we prepared chemically-functionalized water soluble single-walled CNT (SWNT) graft copolymers for modulation of outgrowth of neuronal processes. The graft copolymers were prepared by the functionalization of SWNTs with poly-ethylene glycol (SWNT-PEG). When added to the culturing medium of neurons grown on a standard permissive substratum, these functionalized water soluble SWNTs were able to increase the length of various neuronal processes.

By spraying a film of SWNT-PEG onto hot glass coverslips we created retainable conductive substrates on which we could culture neurons. We could specifically control the conductivity of the substrate by varying the thickness of the nanotube film. We show that conductive nanotubes are biocompatible as substrates for neuronal growth and that the specific level of conductivity is important as it affects neuronal growth and neurite outgrowth.

Taken together these studies demonstrate that CNTs can be used as a scaffold/ substrate for neuronal growth and that modifications of the CNTs can be employed to modulate the arborization of neuronal processes and their outgrowth. This suggests that in the future, it may be possible to employ suitably functionalized CNTs as neural prostheses in neurite regeneration.