A review of the current state of the art in gelatin methacryloyl-based printing inks in bone tissue engineering

Achieving efficient scaffolds for bone tissue engineering (TE) requires smartly defined parameters for reaching a balance between physical–chemical properties, biocompatibility and complex architectures. Three-dimensional (3D) printing offers precise geometry control of the desired scaffold at micro-scale. However, the performance of 3D printing is highly dependent on the formulation, the challenge being to achieve the suitable ink and establish the most efficient printing parameters. Gelatin methacryloyl (GelMA) emerges as a promising ink due to superior biological properties, photocrosslinking ability and printability. The present review focuses on the evolution of GelMA-based inks and bioinks from the simplest to the most advanced multicomponent formulations capable of bone tissue regeneration. Additionally, a comparative analysis between the different photoinitiators is covered, indicating each one's advantages and disadvantages. Furthermore, the main printing and bioprinting methods that are used in GelMA printing are outlined with the required parameters and their influence on the final product performance.