New Visible-Light Photoinitiating System for Improved Print Fidelity in Gelatin-Based Bioinks

Oxygen inhibition is a phenomenon that directly impacts the print fidelity of 3D biofabricated and photopolymerized hydrogel constructs. It typically results in the undesirable physical collapse of fabricated constructs due to impaired cross-linking, and is an issue that generally remains unreported in the literature. In this study, we describe a systematic approach to minimizing oxygen inhibition in photopolymerized gelatin-methacryloyl (Gel-MA)-based hydrogel constructs, by comparing a new visible-light initiating system, Vis + ruthenium (Ru)/sodium persulfate (SPS) to more conventionally adopted ultraviolet (UV) + Irgacure 2959 system. For both systems, increasing photoinitiator concentration and light irradiation intensity successfully reduced oxygen inhibition. However, the UV + I2959 system was detrimental to cells at both high I2959 concentrations and UV light irradiation intensities. The Vis + Ru/SPS system yielded better cell cyto-compatibility, where encapsulated cells remained >85% viable even at high Ru/SPS concentrations and visible-light irradiation intensities for up to 21 days, further highlighting the potential of this system to biofabricate cell-laden constructs with high shape fidelity, cell viability, and metabolic activity.