Enhancing visible light-induced 3D bioprinting: alternating extruded support materials for bioink gelation

In 3D bioprinting, two promising approaches have gained significant attention: the use of support materials during printing and the utilization of bioinks gelled through ruthenium(II) tris-bipyridyl dication ([Ru(bpy)₃]²⁺)-catalyzed photocrosslinking consuming sodium persulfate (SPS). Integrating these approaches while ensuring simplicity and printability remains a challenge. To address this challenge, we propose a technique in which the support material containing SPS is alternately extruded with the bioink containing polymer having phenolic hydroxyl moieties (polymer-Ph) and [Ru(bpy)₃]²⁺under visible light irradiation. This method eliminates the problems of light shading and deformation caused by the support material, as the contact between the alternately extruded ink and the support material initiates the gelation of the ink via photocrosslinking. Using an ink containing 0.5 w/v% hyaluronic acid with phenolic hydroxyl moieties (HA-Ph) and 2.0 mM [Ru(bpy)₃]²⁺alongside a support material containing 10 mM SPS, various constructs were successfully printed under 450 nm visible light. The human hepatoblastoma cells embedded in the printed construct showed approximately 95% viability after printing and proliferation over 14 d of culture. These results highlight the potential of this method to advance 3D bioprinting for tissue engineering applications.