Comparison of Photo Cross Linkable Gelatin Derivatives and Initiators for Three-Dimensional Extrusion Bioprinting

The objective of this study was to evaluate the utility of gelatin–norbornene (GelNB), which is cross-linkable via thiol–ene click chemistry, and the photoinitiator lithium phenyl-2,4,6 trimethyl­benzoyl­phosphinate (LAP) for 3D bioprinting. These materials were compared to two widely used materials, gelatin-methacryloyl (GelMA) and 2-hydroxy-4′-(2-hydroxy­ethoxy)-2-methyl­propiophenone (I2959). Characterization of photocuring kinetics revealed that LAP markedly improved the kinetics compared to I2959, which improved stability and print fidelity. Additionally, GelNB exhibited improved photocuring kinetics, improved stability, and decreased filament spreading compared to GelMA. However, inks containing GelMA yielded at lower stress, were more easily extruded, and produced smoother filaments. NIH 3T3 fibroblasts exhibited high viability in printed constructs, regardless of the gelatin derivative or photoinitiator used. Overall, these results support the selection of LAP over I2959 and suggest that GelNB could be a useful alternative to GelMA, although further work is needed to optimize GelNB extrusion.