Gelatin methacryloyl (GelMA) is just one of many names used to define the gelatin-based, semi-synthetic hydrogel biomaterial used in tissue engineering and regenerative medicine research. GelMA synthesis begins with a gelatin protein backbone which is reacted with inorganic methacryloyl groups, a type of ‘building block’ chemical used to help generate the stability and durability of gelatin methacryloyl. They help with GelMA’s structural integrity by undergoing a crosslinking chemical reaction when mixed with a photoinitiator, like Irgacure 2959 or LAP.

There are two main types of methacryloyl: methacrylate and methacrylamide, both of which are derived from methacrylic anhydride (MA), the ingredient that is added to gelatin during GelMA synthesis. In this process, MA reacts with gelatin in two different ways to form gelatin methacrylate and gelatin methacrylamide. These two products have slightly different chemical makeups, but are functionally the same. Gelatin methacrylate refers to gelatin that has reacted with MA via a substitution reaction, whereas gelatin methacrylamide refers to the GelMA formed when gelatin reacts with MA through an amidification reaction.

When GelMA synthesis occurs, the gelatin typically reacts to form GelMA with more methacrylamide groups than methacrylate groups,however, both are still present. It has thus been suggested that gelatin methacryloyl is a more suitable name as it accounts for the presence of both gelatin methacrylate and gelatin methacrylamide