Theiner, S., 2021
"Three-dimensional (3D) bioprinting is a growing field with an increasing number of possible applications. Besides big goals such as printing whole organs it can also be used to automize and simplify cell culture processing. In this thesis a printing protocol for commercially available nanocellulose based bioinks is established. The cytocompatibility of the used bioinks is tested using adipose derived stem cells (ASCs). The used nanofibrillar cellulose (NFC) bioinks, GrowDex, GrowDex-T, GrowInk-T and Laminink+ are first tested on their printability and correct dilutions. The behavior of cells inside the bioinks was observed over 14 days to assess the cytocompatibility of the tested bioinks. The main parameter to be tested is the concentration of the bioinks, as it affects the printability of the ink and the viability of the cells inversely. Therefore, the right mixing ratio of bioink and cell suspension is needed for the bioink to still be printable in a stable structure, with favorable conditions for proliferation and migration of cells. As GrowDex and GrowInk-T did not fulfill both of these requirements they were eliminated from further testing. GrowDex-T and Laminink+ were selected as the inks with the best properties. As a final preparation step the effects of manual deposition and extrusion bioprinting on the cells are observed. Droplets of the same size are manually deposited and bioprinted. After observing that there is no significant difference in cell survival and cell proliferation, between manual deposition and extrusion bioprinting, the final cell migration experiment is conducted. Stripes of cell-free bioink and cell-containing bioink are printed next to each other and the behavior of cells is observed over two weeks. Overall, the cells grow outside of the printed structure and do not invade the unseeded stripes of bioink. In GrowDex-T, with a concentration of 0.8 %, cells show better proliferation and change their morphology from a round to a spindle shape. Cells in Laminink+, mixed in a ratio of 2:1 with cell suspension, do not change significantly but also do not die. These experiments show that cells can be cultured in NFC hydrogels for bioprinting. From the tested bioinks GrowDex-T is the best candidate as it has the best printing properties, while providing stable structures for long-term culturing of ASCs."
Theiner, S., Extrusion 3D Bioprinting of nanocellulose based bioinks, Vienna University of Technology, 2021.