Embedding bioprinting of low viscous, photopolymerizable blood-based bioinks in a self-healing transparent supporting bath

Protein-based hydrogels have great potential to be used as bioinks for biofabrication-driven tissue regeneration strategies due to their innate bioactivity. Nevertheless, their use as bioinks in conventional 3D bioprinting is impaired due to their intrinsic low viscosity. Using embedding bioprinting, a liquid bioink is printed whithin a support that physically holds the patterned filament. Inspired by the recognized microencapsulation technique complex coacervation, we introduce crystal self-healing embedding bioprinting (CLADDING) based on a highly transparent crystal supporting bath. The suitability of distinct classes of gelatins was evaluated (i.e., molecular weight distribution, isoelectric point and ionic content), as well as the formation of gelatin-gum arabic microparticles as a function of pH, temperature, solvent and mass ratios. Characterizing and controlling this parametric window resulted in high yields of support bath with ideal self-healing properties for interaction with protein-based bioinks during bioprinting. This support bath achieved transparency, which boosted light permeation within the bath. CLADDING bioprinted constructs fully composed of platelet lysates encapsulating a co-culture of human mesenchymal stem cells and endothelial cells were obtained, demonstrating high-dense cellular network with excellent cell viability and stability over a month. CLADDING broadens the spectrum of photocrosslinkable materials with extremely low viscosity that can now be bioprinted with sensitive cells using embedding bioprinting without any additional support.