Design Strategies for Tissue Engineering Scaffolds

This thesis focuses on various aspects involved in scaffold design and the cell-scaffold interaction. The ultimate goal is to design a scaffold that supports functional tissue formation, resembling in vivo tissue organization, combined with good nutrient supply to the cells. In our concept 3D multi-layer scaffolds are developed consisting of porous micropatterned sheets fabricated by one-step method phase separation micromolding (PSµM). In these multi-layer scaffolds, the cells grow within micropatterned channels giving clear direction to the cells inducing cell organization. Subsequent stacking of these sheets results in 3D scaffolds where the microchannels also provide space for nutrient perfusion throughout the complete scaffold. The porosity of the individual layers enables diffusion of nutrients and signalling factors between the layers. First, an overview is presented of commonly applied biomaterials as well as fabrication techniques to process these materials into scaffolds, which in contrast to PSµM generally only incorporate or porosity or surface topography. Subsequently, the understanding and optimization of the PSµM processing conditions are considered to obtain these micropatterned porous scaffold sheets of distinct polymers varying largely in material properties, of which poly(L-lactic acid) (PLLA) is the most commonly applied. Adapting PSµM process parameters yields micropatterned sheets expressing a wide variety of porosities and morphologies. With respect to the cell-material interactions, the results reveal clear organization of the cells for distinct surface topographies, independently of the scaffold material. In addition, a detailed study is presented that relates the influence of scaffold material and micropatterning to surface wettability and protein adsorption, and in turn their effect on cell attachment, proliferation and morphology. Furthermore, we present a new high-throughput screening concept of a large surface characteristics library to enable selection of surface characteristics that elicit an appropriate bio-active response required for a specific application. Finally, the transport of nutrients throughout the 3D multi-layer scaffold is studied under both static as well as dynamic (perfusion) conditions. Nutrient perfusion through the microchannels of the scaffold clearly revealed improved cell viability and proliferation at the distinct layers showing the excellent potential of the multi-layer 3D scaffolds as proposed in this thesis.