Hydrolytic Stability of Methacrylamide and Methacrylate in Gelatin Methacryloyl and Decoupling of Gelatin Methacrylamide from Gelatin Methacryloyl through Hydrolysis

Abstract

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/macp.201800266. HydrolysisGelatin methacryloyl (GelMA; GM) is a promising nature-derived photocurable material that can mimic the extracellular matrix because GelMA features tailorable mechanical properties, proteolytic degradation, and good cell adhesion. GelMA contains not only methacrylamide but also methacrylate. However, the hydrolytic stability of methacrylamide and methacrylate groups of GelMA in aqueous solutions has not been scrutinized. Here, the structural change of GelMA through hydrolysis is investigated for the first time. The structural change of hydrolyzed GelMA is quantitatively identified using colorimetric and 1 H NMR methods. The methacrylate groups decompose markedly at high pH solutions, but the methacrylamide groups remain stable. Further, pure gelatin methacrylamide is successfully decoupled from GelMA for a better understanding of GelMA structure and future use for biomedical applications.

Gelatin methacryloyl and its hydrogels with an exceptional degree of controllability and batch-to-batch consistency

“…In this respect, a one-pot reaction strategy using the CB buffer at around pH 9 (above the isoelectric point of gelatin) could be ideal, and easy to control the reaction parameters 20 . On the other hand, the CB buffer at even higher pH (pH 11 and 12) can degrade quickly MAA as well as the formed methacrylate groups through hydrolysis, which is not so effective for GelMA synthesis 26 . The buffer capacity of the CB buffer was found to be optimal at around 0.25 M. Another important thing of GelMA synthesis is to improve the miscibility of two reactants (gelatin and MAA) because gelatin is soluble in warm water whereas MAA is insoluble in water.…”

“…Glycine-Proline-hydroxyproline tripeptides have been found to participate in the triple helix formation 29–31 . Hydroxyl groups of hydroxyproline can react with methacrylic anhydride (MAA) especially in a high feed of MAA 25,26 . Highly substituted GelMA (DS100_1~5) possessed the methacrylate group of around 0.01 mmole g −1 most likely from the reaction of hydroxyproline and MAA, which is presumed to obstruct partially the triple-helix formation.…”

Rheological Properties of Coordinated Physical Gelation and Chemical Crosslinking in Gelatin Methacryloyl (GelMA) Hydrogels

“…Free‐radical photopolymerization of GelMA results in chemical crosslinks between methacrylamide and methacrylate groups on the gelatin backbone. [ 55,56 ] This randomly organized crosslinking strategy results in hydrogels that have proportionally stronger mechanical properties with higher available crosslinks, controlled by the DS during synthesis or the available free amines for modification in gelatin. [ 18 ] Storage modulus ( G ′) is highest for GelMA hydrogels with the highest DS.…”

Expanding the Range of Available Isoelectric Points of Highly Methacryloylated Gelatin

“…The latter observation could, however, be due to hydrolysis during dialysis. Generally, side reactions during EDA modification are shown to be especially relevant for gelatins which contain substantial amounts of methacrylate groups and could consequently be avoided in the future by using, for example, GMs containing only methacrylamide groups . Another method to avoid side reactions would be employing protective group chemistry for one of the two amino groups in EDA in order to be able to avoid the large excess of EDA used in the modification reaction.…”