No abstract

Porous membranes are ubiquitous in cell co-culture and tissue-on-a-chip studies. These materials are predominantly chosen for their semi-permeable and size exclusion properties to restrict or permit transmigration and cell-cell communication. However, previous studies have shown pore size, spacing and orientation affect cell behavior including extracellular matrix production and migration. The mechanism behind this behavior is not fully understood. In this study, we fabricated micropatterned non-fouling polyethylene glycol (PEG) islands to mimic pore openings in order to decouple the effect of surface discontinuity from potential grip on the vertical contact area provided by pore wall edges. Similar to previous findings on porous membranes, we found that the PEG islands hindered fibronectin fibrillogenesis with cells on patterned substrates producing shorter fibrils. Additionally, cell migration speed over micropatterned PEG islands was greater than unpatterned controls, suggesting that disruption of cell-substrate interactions by PEG islands promoted a more dynamic and migratory behavior, similarly to enhanced cell migration on microporous membranes. Preferred cellular directionality during migration was nearly indistinguishable between substrates with identically patterned PEG islands and previously reported behavior over micropores of the same geometry, further confirming disruption of cellsubstrate interactions as a common mechanism behind the cellular responses on these substrates. Interestingly, compared to respective controls, there were differences in cell spreading and a lower increase in migration speed over PEG islands compared prior results on micropores with identical feature size and spacing. This suggests that membrane pores not only disrupt cell-substrate interactions, but also provide additional physical factors that affect cellular response.

No abstract

Cellular processes are linked to the alignment (anisotropy) and orientation (directionality) of collagen fibers (i.e., landscape) in the native extracellular matrix (ECM). Given the vital role that cell‐matrix interactions play in regulating biological functions, several microfluidic methods have successfully established anisotropic 3D collagen gels to develop quantitative relationships between structural cues and cellular responses. However, independently tailoring the fiber anisotropy and fiber directionality within a landscape remains a challenge. Here, a user‐friendly microfluidic platform with a non‐uniform channel geometry is used to control the degree of fiber anisotropy and directionality as a function of extensional strain rate and a defined flow path, respectively. New experimental capabilities, including independent control over the degree of fiber anisotropy and directionality, spatial gradients in anisotropy, and multi‐material interfaces, are demonstrated. A channel peel‐off technique provides direct access to the microengineered collagen landscapes, and the alignment of single MD‐MB‐231 cancer cells and monolayers of human umbilical vein endothelial cells (HUVEC) is shown. Finally, the platform's modular capability is highlighted by integrating an ultrathin porous Parylene (UPP) membrane onto the microengineered collagen landscape as a method to control the degree of cell‐matrix interaction.