Physico-chemical properties and cytotoxicity of gelatin methacryloyl crosslinked with nanoparticle photoinitiator

Diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) fabricated into nanoparticle form with increased water dispersibility has enabled broader applications for the bioprinting of hydrogel scaffolds. In this study, the use of TPO NP as a photoinitiator for bioprinting gelatin methacrylate (GelMA) was compared with commonly used lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) photoinitiator by assessing the physico-chemical properties, mechanical strength, gelation kinetics, resistance to flow, absorptivity in different solvents, and biological responses. The results demonstrated that the physico-chemical and mechanical properties of the GelMA were similar using LAP and TPO nanoparticles (NP) for crosslinking. The significant cytotoxicity observed in cells exposed to the GelMA with TPO NP suggests that cell-embedded bioprinting may not be feasible and that removal of toxicant may be needed to utilize GelMA scaffolds crosslinked with TPO NP for biological applications. The results of this study provide a framework for future studies that will consider the microstructure and in vitro properties of GelMA.