Fig 1. Synthesis of fish gelatin methacryloyl (GelMA) and fabrication of photocrosslinked GelMA hydrogel.

(A) Gelatin was reacted with methacrylic anhydride (MA) to introduce a methacryloyl substitution group on the reactive amine and hydroxyl groups of the amino acid residues. (B) GelMA photocrosslinking to form A hydrogel matrix under UV irradiation. The free radicals generated by the photoinitiator initiated chain polymerization with methacryloyl substitution. (C) Schematic of formation of patterned hydrogels using photolithography.