3D printing of alginates into tubular structures resembling human airways

Abstract: Tissue shortage for lung transplantation remains a problem worldwide as lung transplantation is often the only available option with numerous possible complications. Generating lung tissue ex-vivo has been proposed as one way to potentially overcome this shortage. For this, tissue engineering is one potential strategy to either repair, replace or regenerate damaged tissue and organs. In this thesis, several experiments were conducted with the goal of improving the 3D printing process of sodium alginate using a modified 3D printer and thus, enabling more reproducible and consistent results. The morphology of the sodium alginate after crosslinking with calcium chloride was studied and compared between different alginate types and concentrations. Similarly to previous studies, it was found that both alginate type and concentration made an impact on parameters such as dissolution over time, ability to be crosslinked into a stable hydrogel, and use in extrusion-based 3D printing. The morphology of tubular alginate structures after crosslinking was also investigated, and any shape or size changes due to the crosslinking itself and independent from the 3D printing method. Additionally, data was gathered on how the crosslinked alginate degraded or dissolved after a number of days in an environment simulating a cell culture. It was found that the resorption rate varied between different sodium alginate types. Furthermore, 3D printing parameters were explored in order to accurately print 3D models of tubular structures with controlled shape and size and consideration to alginate behavior. There were discrepancies found in the comparison between the digital rendering and the actual final print. However, the project resulted in suggestions for future improvements of the current techniques. The various parameters investigated in this thesis can with further studies lead to printing with higher precision and accuracy of final prints.