Fig 2. Degree of methacrylation as determined by TNBS assay.

(A) Various volume percentages of methacrylic anhydride (0.25%, 1.25% and 20%) were analyzed to investigate the degree of methacrylation of the synthesized fish GelMA. (B) Comparison of a high degree of methacrylation (20% MA) according to the origin of gelatin (fish GelMA vs. porcine GelMA); there was no significant difference. The percentage of incorporated substitution was calculated by comparing the amount of remaining amino groups (-NH₂) in GelMA to that in pristine gelatin. Error bars represent standard deviations (SDs) of measurements performed on six samples.