Rolled graphene oxide foams as three-dimensional scaffolds for growth of neural fibers using electrical stimulation of stem cells

Graphene oxide foam (GOF) layers with thicknesses of similar to 15-50 mu m and density of similar to 10 graphene oxide (GO) sheets/mu m were fabricated by precipitation of chemically exfoliated GO sheets in an aqueous suspension at similar to 80 degrees C under UV irradiation. Then, rolled GOFs with desirable scales were developed as electrically conductive 3D-scaffolds and applied in directional growth of neural fibers, through differentiation of human neural stem cells (hNSCs) into neurons under an electrical stimulation. X-ray photoelectron spectroscopy indicated that the UV irradiation resulted in partial deoxygenation of the layers. Scanning electron microscopy and Raman spectroscopy confirmed the presence of multilayer GO sheets in the foam structure. The electrical sheet resistance of the GOFs was found low enough to produce the electrical stimulation currents used in differentiation of the neural cells, under low voltages. Rolling the GOFs (with hydrophilic surfaces) resulted in formation of cross-sections with superhydrophilic characteristics, inducing effective proliferation and differentiation of the hNSCs throughout the pores and interfaces of the scaffold. The electrical stimulation induced more proliferation of the cells and acceleration of the differentiation into neurons (rather than glia). These results suggest the GOFs as flexible and conductive scaffolds for regeneration of nervous systems and tissue engineering. (C) 2015 Elsevier Ltd. All rights reserved.