The use of graphene in the self-organized differentiation of human neural stem cells into neurons under pulsed laser stimulation.

An effective and self-organized differentiation of human neural stem cells (hNSCs) into neurons was developed by the pulsed laser stimulation of the cells on graphene films (prepared by drop-casting a GO suspension onto quartz substrates). The effects of graphene oxide (GO) and hydrazine-reduced graphene oxide (rGO) sheets on the proliferation of hNSCs were examined. The higher proliferation of the cells on the GO was assigned to its better hydrophilicity. On the other hand, the rGO sheets, which have significantly better electrical conductivity than GO, exhibited more differentiation of the cells into neurons. The pulsed laser stimulation not only resulted in an accelerated differentiation of hNSCs into neurons (rather than glia), but also caused the self-organization of a radial neuronal network on the surface of the rGO sheets, due to the radial stress induced by the surface thermal gradient originating from the center of the laser spot. The higher thermal conductivity of the rGO sheets (compared to the GO sheets and the quartz substrate) provided better outward heat flow from the center of the laser spot, and consequently, prevented extra local heating at the position of the laser spot. These results can encourage further investigations into the advantages of graphene in the self-organized differentiation of hNSCs using pulsed laser stimulation.