The introduction of methacrylamide groups in the gelatin was conducted according to the method reported by Li, 47 with modifications. First, 5 g of gelatin were dissolved in 45 mL of PBS at 50 °C under constant magnetic stirring. Then, 167 μL of methacrylic anhydride (94%) were added dropwise every 30 minutes for 2.5 h (6 additions, 1 mL total). After the last addition, the mixture was left to react for another 30 minutes. Next, the reaction was stopped by adding 100 mL of PBS, and the product was dialyzed against ultrapure water (18.2mΩ•cm from a Reference A10+ Millipore System, Z00QSVC01 Millipore S.AS., Molsheim, Bas-Rhib, France, subsequently referred to simply as water) for 7 days at 37 °C, with two daily water changes.