Andrew Lee, Graduate Student, Carnegie Mellon University
Adam Feinberg PhD, Associate Professor, Carnegie Mellon University
3D printing is an emerging approach in biofabrication because it is capable of forming complex scaffolds for tissue engineering applications. However, current techniques have been limited in material selection, and geometric complexity is challenging for soft materials that easily deform, such as the extracellular matrix (ECM) proteins collagen I and fibrinogen. To address this, we developed Freeform Reversible Embedding of Suspended Hydrogels (FRESH), which extrudes (embeds) and gels ECM solutions within a thermoreversible support bath. Here, we used FRESH to biofabricate cardiac tissues by printing collagen type I scaffolds with controlled topology and mechanical anisotropy to induce cellular alignment and contractility. Human induced pluripotent stem cell (iPSC) derived cardiomyocytes were seeded onto printed scaffolds, cultured for 14 days, and then assessed for print fidelity, tissue morphology, and cellular alignment. Preliminary results show that collagen sheets with parallel ridges of 120 μm width and spacing could be printed and that infill percent and design could be utilized to locally pattern mechanical properties within the sheets. Cardiomyocytes showed high viability and well-defined sarcomeres and achieved visible contraction of the entire construct after 8 days in culture. These results demonstrate that the FRESH bioprinting process engineer anisotropic cardiac tissues using ECM protein bioinks.