Investigation of gelatin methacrylate working curves in dynamic optical projection stereolithography of vascular-like constructs

3D Bioprinting is continuing to emerge as a promising approach for the manufacturing of 3D vascular constructs by the utilization of a layer-by-layer fabrication methodology. The working curve represents the interaction between the UV and the photocrosslinkable materials, which is of great importance to the printing resolution and quality during dynamic optical projection stereolithography of vascular-like constructs. Two important material optical properties are revealed from the working curve: The depth of UV penetration, D_p, which indicates the depth that projected UV into the bioink can reach, after which there is a reduction in irradiance of 1/e, and the critical energy level, E_c, which indicates the amount of UV energy that is needed in order to initiate the crosslinking of the photopolymer. This study focuses on the working curves of the gelatin methacrylate (GelMA) with different polymer concentrations, photoinitiator concentrations, and degrees of functionalization (DoF). It is found that an increase of the polymer and photoinitiator concentrations results in the slight decrease of the UV penetration depth from 0.61 mm to 0.55 mm while the critical UV energy increases slightly from 48 mJ/cm² to 61 mJ/cm². When the GelMA DoF is increased, the UV penetration depth decreases significantly from 1.9 mm to 0.61 mm and the critical UV energy decreases significantly from 1189 mJ/cm² to 48 mJ/cm². Finally, the fabrication of a 3D four-branch vascular-like construct with cells encapsulated has been performed by using DMD-based dynamic optical projection stereolithography, and cell viability is evaluated to be 80% after 48-hour incubation.