Engineering Mechanically Tunable Elastin-Based Microgel Bioinks: From Microscale Stiffness Control to Macroscale Structural Bioprinting

Microgel bioinks have gained great potential in bioprinting and tissue engineering due to their excellent mechanical performance and versatile printability. However, the effect of microgel size on the mechanical properties and printability remained to be thoroughly explored. In this study, we developed an injectable gelatin-elastin methacrylate (GelMA-ElaMA) microgel bioink with tunable microgel diameters (100-1000 μM) using a microfluidic approach. The bioink's mechanical properties were systematically characterized through compression tests, AFM nanoindentation, and finite element analysis (FEA). Larger microgel bioinks exhibited higher stiffness, whereas the smaller ones showed greater flexibility and fracture strain. The FEA results confirmed a size-dependent enhancement of the modulus at the microscale. The bioinks displayed excellent printability and could form complex 3D structures with high shape fidelity. Microgel size modulates the stiffness-dependent cell response. When magnetically functionalized, the system responded to external magnetic fields and supported cell viability above 90%. These findings established a theoretical basis for microgel bioink design with mechanical tunability.