Graphene nanogrids for selective and fast osteogenic differentiation of human mesenchymal stem cells

Graphene nanogrids (fabricated by graphene nanoribbons obtained through oxidative unzipping of multi-walled carbon nanotubes) were used as two-dimensional selective templates for accelerated differentiation of human mesenchymal stem cells (hMSCs), isolated from umbilical cord blood, into osteogenic lineage. The biocompatible and hydrophilic graphene nanogrids showed high actin cytoskeleton proliferations coinciding with patterns of the nanogrids. The amounts of proliferations were found slightly better than proliferation on hydrophilic graphene oxide (GO) sheets, and significantly higher than non-uniform proliferations on hydrophobic reduced graphene oxide (rGO) sheets and polydimethylsiloxane substrate. In the presence of chemical inducers, the reduced graphene oxide nanoribbon (rGONR) grid showed a highly accelerated osteogenic differentiation of the hMSCs (a patterned differentiation) in short time of 7 days in which the amount of the osteogenesis was ～2.2 folds greater than the differentiation (a uniform differentiation) on the rGO sheets. We found that although in the absence of any chemical inducers the graphene nanogrids showed slight patterned osteogenic differentiations, the graphene sheets could not present any differentiation. Therefore, the highly accelerated differentiation on the rGONR grid was assigned to both its excellent capability in adsorption of the chemical inducers and physical stresses induced by the surface topographic features of the nanogrids.