Cellular interactions with protein nanofibers

Abstract

The fundamental understanding of cell-material interactions plays a central role in the development of future biomaterials for tissue engineering. The current state of knowledge about cell interactions with various biomaterials has mainly been obtained from smooth 2D-cell culture systems like petri dishes. However, many of the established materials are not suitable for mimicking the nanofibrous three-dimensional (3D) topography, the biochemical and mechanical environment of the extracellular matrix (ECM). This raises the challenge of transferring cell culture results from established smooth/planar test systems into the development of novel 3D microenvironments that mimic the nanoarchitecture of the ECM. Therefore, in this Ph.D. thesis, a new approach for the fabrication of binary protein scaffolds with spatially controlled areas of smooth and nanofibrous topography was introduced. First, the ECM protein collagen was used as a model system to establish the new method. Polymer patterning was combined with pH-induced self-assembly and crosslinking of collagen to produce binary scaffolds with spatially controlled smooth nanofibrous topographies. When studying the interaction of NIH 3T3 fibroblasts with the new binary scaffolds, a direct influence of the underlying topography on cell morphology, cell size, filopodia growth and cell migration was observed. To further investigate the influence of biochemical cues on cells, the novel method of preparing binary collagen scaffolds was subsequently transferred to the model system fibrinogen. The new process was successfully combined with the newly introduced salt-induced fibrinogen self-assembly. When investigating the interaction of fibroblasts with binary fibrinogen scaffolds, a direct influence of the underlying topography on cell morphology was observed. Fluorescence microscopy analysis revealed that the morphology of fibroblasts changed from small spindle-like shape with diffuse actin expression on fibrinogen nanofibers to large, flat cells with pronounced stress fibers on planar fibrinogen. Moreover, viability studies of fibroblasts on fibrinogen showed increased proliferation rates on both, nanofibrous and planar, fibrinogen scaffolds. Subsequently, the two protein systems and topographies were combined in one scaffold system.