Spatial patterning of nanofibrous collagen scaffolds modulates fibroblast morphology.

Current knowledge about cell-biomaterial interactions is often based on two-dimensional (2D) cell culture systems like protein-coated glass slides. However, such smooth surfaces cannot mimic the nanofibrous environment of the native extracellular matrix (ECM). It is therefore a major challenge to transfer the results from 2D surfaces to 3D protein scaffolds with biomimetic nanofiber architecture. To understand the influence of different protein topographies on the cell response we introduce a new process to fabricate binary collagen scaffolds of variable thickness with spatially controlled regions of nanofibrous and smooth topography. We used pH-induced self-assembly to prepare collagen nanofibers with diameters between 130 and 150 nm on glass surfaces, which were partly covered with a polymer mask. After cross-linking with glutaraldehyde, smooth collagen films were prepared on the remaining glass regions. Atomic force microscopy revealed a much lower surface roughness of smooth collagen compared to nanofibers. Subsequently, we studied the viability, morphology and migration of 3T3 fibroblasts on both collagen topographies. We found small, elongated fibroblasts with few, long filopodia on collagen nanofibers whereas large, flat fibroblasts with many short filopodia were observed on smooth collagen. Actin stress fibers on collagen nanofibers were substantially reduced in comparison to smooth collagen. Live cell tracking revealed that fibroblasts on thin nanofibrous collagen migrated faster than on smooth collagen. In summary, binary collagen scaffolds enabled us for the first time to study cell responses to topographical cues on a single protein scaffold. In future, it will be intriguing to transfer our patterning process to other proteins to study fundamental principles of topography-dependent cell recognition processes.