Structure and Properties of Gelatin Methacryloyl (GelMA) Synthesized in Different Reaction Systems

Gelatin methacryloyl (GelMA) hydrogels have been extensivelyusedfor drug delivery and tissue engineering applications due to theirgood biocompatibility, biodegradability, and controllable photocurableefficiency. Phosphate buffer solution (PBS) is the most widely usedreaction system for GelMA synthesis. However, carbonate-bicarbonatebuffer solution (CBS) has been tried recently for synthesizing GelMAdue to its high reaction efficiency. However, there is a lack of systematicinvestigation into possible differences in the structure and propertiesof GelMA synthesized in PBS and CBS, respectively. Therefore, in thecurrent study, GelMA molecules with two degrees of methacryloylation(similar to 20 and similar to 80%) were synthesized under PBS and CBS reactionsystems, respectively, in comparable conditions. The results showedthat because of the functionalization of methacrylate groups in gelatinchains, which could interfere with the intrachain and interchain interactions,such as hydrogen bonding, the GelMA molecules synthesized in PBS haddistinct physical structures and exhibited different properties incomparison with those produced in CBS. GelMA hydrogels synthesizedin PBS exhibited higher gel-sol transition temperatures andbetter photocurable efficiencies, mechanical strength, and biologicalproperties. In contrast, GelMA hydrogels produced in CBS showed advantagesin swelling performance and microstructures, such as pore sizes andporosities. In addition, GelMA synthesized in PBS and possessing ahigh degree of methacryloylation (the "GelMA-PH" polymer)showed great potential for three-dimensional (3D) bioprinting. Thisfocused study has gained helpful new insights into GelMA and can provideguidance on the application of GelMA in 3D printing and tissue engineering.