The influence and interactions of substrate thickness, organization and dimensionality on cell morphology and migration.

Cells reside in a complex microenvironment in situ, with a number of chemical and physical parameters interacting to modulate cell phenotype and activities. To understand cell behavior in three dimensions recent studies have utilized natural or synthetic hydrogel or fibrous materials. Taking cues from the nucleation and growth characteristics of collagen fibrils in shear flow, we generate cell-laden three-dimensional collagen hydrogels with aligned collagen fibrils using a simple microfluidic device driven by hydrostatic flow. Furthermore, by regulating the collagen hydrogel thickness, the effective surface stiffness can be modulated to change the mechanical environment of the cell. Dimensionality, topography, and substrate thickness/stiffness change cell morphology and migration. Interactions amongst these parameters further influence cell behavior. For instance, while cells responded similarly to the change in substrate thickness/stiffness on two-dimensional random gels, dimensionality and fiber alignment both interacted with substrate thickness/stiffness to change cell morphology and motility. This economical, simple to use, and fully biocompatible platform highlights the importance of well-controlled physical parameters in the cellular microenvironment.