3d-Printed Gelatin-Based Bioinks: A Review of L929 Fibroblast Viability and in Vitro Scratch Assay Dynamics

Gelatin-based bioinks have become widely used in 3D bioprinting because they support cell growth and can be easily modified for printing. However, the way these inks are prepared—particularly through crosslinking and extrusion—can either help or harm the cells inside them. This review brings together findings from two common tests: the L929 cytotoxicity assay, which checks if the material is toxic to cells, and the scratch assay, which measures how well cells can move and close a wound-like gap. Our analysis shows that while stiffer gels hold their shape better during printing, they often slow down cell movement, and that high shear stress during extrusion can temporarily damage cells. We also highlight major challenges, including poor reporting standards and the limited relevance of mouse-derived cell lines to human biology. To move the field forward, we recommend adopting standardized reporting guidelines, using artificial intelligence to optimize printing conditions, and transitioning to human primary cells for more meaningful results.