Alignment of Carbon Nanotubes: An Approach to Modulate Cell Orientation and Asymmetry.

Stem cells offer a promising tool in tissue engineering strategies, as their differentiated derivatives can be used to reconstruct most biological tissues. These approaches rely on controlling the biophysical cues that tune the ultimate fate of cells. In this context, significant effort has gone to parse out the role of conflicting matrix-elicited signals (e.g., topography and elasticity) in regulation of macroscopic characteristics of cells (e.g., shape and polarity). A critical hurdle, however, lies in our inability to recapitulate the nanoscale spatiotemporal pattern of these signals. The study presented in this manuscript took an initial step to overcome this challenge by developing a carbon nanotube (CNT)-based substrate for nanoresolution control of focal adhesion formation and cell alignment. The utility of this system was studied using human umbilical vascular endothelial cells (HUVECs) and human embryonic stem cells (hESCs) at a single cell level. Our results demonstrated the ability to control cell orientation by merely controlling the alignment of focal adhesions at a nanoscale size. Our long-term vision is to use these nanoengineered substrates to mimic cell orientation in earlier development and explore the role of polarity in asymmetric division and lineage specification of dividing cells.