Development of standardization strategies for reproducible extrusion-based 3D bioprinting processes

In the last decade, Additive Manufacturing (AM) has evolved from a specialized niche application to a widely used standard tool that has become indispensable in many areas of research and industry. Due to new technologies and materials enabling the fabrication of high quality products, AM is not only relevant for Rapid Prototyping, but also in the fabrication of products for end users. Especially when a high degree of customization or geometrical complexity is involved, AM methods can be considered as viable options. In medicine and biochemical engineering, AM is typically employed for applications like the fabrication of dental implants and mouthguards or for customized lab equipment, microfluidic devices and even chromatography columns. The combination of biological materials and living cells with AM methods has resulted in the establishment of bioprinting as a separate field with new opportunities and challenges. Bioprinting methods allow the fabrication of soft, water-based materials suitable for the physical entrapment of enzymes. This allows biocatalytic reactors to be directly printed using enzyme-loaded inks. The present thesis aims at extending the toolbox for the fabrication of biocatalytically active materials with a focus on extrusion-based bioprinting. Novel inks are established in combination with specifically adapted printing setups to achieve enhanced printability. To assess the performance of different materials regarding the resulting biocatalytic activity, microplate-based activity assays are established for two different enzymes. The inks and hydrogels are characterized using a range of additional analytical methods like rheology, mechanical testing or scanning electron microscopy. To determine the permeability of hydrogels for substrate molecules, a microfluidics-based method for the estimation of diffusion coefficients in hydrogels is developed. As a general contribution to the improvement of process monitoring and control in extrusion-based bioprinting, a PID-based pressure control is ...