Gelatin Methacrylation for Biomaterials

Gelatin was methacrylated in accordance with the protocol described elsewhere^{31 (link), 32 (link)}. In brief, 10g of bovine skin gelatin (Sigma Aldrich, St. Louis, MO, USA) was dissolved in 100 mL of PBS and stirred at 60 °C for roughly 1 hour to achieve complete solvation. Next the solution was lowered to 50°C, after which, 8mL of methacrylic anhydride (cat no.: 276685; Sigma Aldrich) was added to the solution drop wise with vigorous stirring. The solution was kept at 50°C with vigorous stirring for an hour after the addition was complete, after which, it is quenched with 2x the volume of PBS (200 mL). The solution was then dialyzed against milliQ water using 12–14 kDa cutoff dialysis tubing (Spectrum Laboratories, Rancho Dominguez, CA, USA) for one week (3 times per day water change) at 40 °C to remove trace contaminants. Next, the GelMA solution was frozen in liquid nitrogen and lyophilized in a freeze dryer for 4 days before being stored at −20 °C until usage.