3D bioprinting of molecularly engineered PEG-based hydrogels utilizing gelatin fragments.

Three-dimensional (3D) bioprinting is an additive manufacturing process in which the combination of biomaterials and living cells, referred to a bioink, are deposited layer-by-layer to form biologically active 3D tissue constructs. Recent advancements in the field show that the success of this technology highly depends on the development of novel biomaterials or the improvement of existing bioinks for bioprinting. Polyethylene glycol (PEG) is one of the well-known synthetic biomaterials and has been commonly used as a photocrosslinkable bioink for bioprinting. In this work, we proposed a novel micro-capillary based approach for bioprinting of molecularly engineered PEG-based bioink. PEG was firstly functionalized with cell-adhesive RGD ligands, which was then cross-linked using protease-sensitive peptides via Michael-type addition reaction inside the micro-capillary before bioprinting processes. Low molecular weight gelatin fragments (LMWG) were supplemented into the bioink to extrude smooth cylindrical strands of the hydrogel for shape fidelity. The cells encapsulated in the bioprinted PEG-based bioink showed high viability and continued to proliferate over time in culture in well-defined cell-morphology. In summary, the presented micro-capillary based bioprinting process for a PEG-based hydrogel system can be promising to construct the complex 3D structures with spatiotemporal variations without using any cytotoxic photoinitiator, UV light, or polymer support.