Nanofiber Size-dependent Sensitivity of Fibroblast Directionality to the Methodology for Scaffold Alignment

The sensitivity of fibroblast guidance on directional cues provided by aligned nanofibers is studied for scaffolds of successively smaller fiber sizes (740±280, 245±85, 140±40, and 80±10 nm) fabricated using mandrel and electrical alignment methodologies for electrospun nanofibers (∼10° angular deviation (AD)), as well as nanoimprint methodologies for perfectly aligned fibers (0° AD). On aligned scaffolds of large fibers (∼740 nm) cell directionality closely follows the underlying fibers, irrespective of the alignment method. However, on mandrel aligned scaffolds of successively smaller fibers the cell directionality exhibits greater deviations from the underlying fiber alignment due to the higher likelihood of interaction of cell lamellipodia with multiple, rather than single, nanofibers. Using electrically aligned scaffolds, fibroblast directionality deviations can be maintained in the range of nanofiber alignment deviation for fiber sizes down to ∼100 nm. This improvement in cell guidance is attributed to molecular scale directional adhesion cues for cell receptors, which occur within electrically aligned scaffolds due to fiber polarization parallel to the geometric alignment axis of the nanofiber under the modified electric field during electrospinning. While fibroblast directionality is similar on electrically aligned vs. nanoimprinted scaffolds for fiber sizes >100 nm, cell directionality is influenced more strongly by the perfect alignment cues of the latter on ∼100 nm fiber scaffolds. The scaffold alignment methodology is hence highly significant, especially for tissue engineering applications requiring sub-100 nm aligned fibers.