  Several works reported increased differentiation of neuronal cells grown on
graphene; however, the molecular mechanism driving axon elongation on this
material has remained elusive. Here, we study the axonal transport of nerve
growth factor (NGF), the neurotrophin supporting development of peripheral
neurons, as a key player in the time course of axonal elongation of dorsal root
ganglion neurons on graphene. We find that graphene drastically reduces the
number of retrogradely transported NGF vesicles in favor of a stalled
population in the first two days of culture, in which the boost of axon
elongation is observed. This correlates with a mutual charge redistribution,
observed via Raman spectroscopy and electrophysiological recordings.
Furthermore, ultrastructural analysis indicates a reduced microtubule distance
and an elongated axonal topology. Thus, both electrophysiological and
structural effects can account for graphene action on neuron development.
Unraveling the molecular players underneath this interplay may open new avenues
for axon regeneration applications.
