A mechanically robust thixotropic collagen and hyaluronic acid bioink supplemented with gelatin nanoparticles

Bioprinting has become an essential tool of biomedical engineering and regenerative medicine. However, current biologically relevant bioinks, i.e. printing materials made from materials found within the extracellular matrix, are unable to support themselves and require a sacrificial support material to create large structures. To address this issue, we have developed a novel thixotropic bioink made from methacrylated collagen I, thiolated hyaluronic acid, and gelatin nanoparticles which is self-supporting and capable of creating large hollow structures through bioprinting. Once printed, this material can be photo-crosslinked to finalize the structure and can be immerse in media for culture with minimal swelling. An intersecting tubular structure 5 mm in diameter with a 1 mm wall thickness was able to be printed longitudinally without support material using a CellInk BIOX bioprinter. This bioink was also able to support HepG2 cells in bioprinted organoids, with adenosine triphosphate assays and immunohistochemistry showing proliferation. Responses to acetaminophen and troglitazone were as expected, proving that the new bioink does not significantly alter HepG2 drug response. With great mechanical properties as well as good biocompatibility, this new biologically relevant bioink is a great improvement over current bioinks.