Thomas J. Hinton, Doctoral Student, Carnegie Mellon University
Adam Feinberg PhD, Associate Professor, Carnegie Mellon University
Collagen type I (COL1) is the most abundant extracellular matrix (ECM) protein in the human body, making it an important material in 3D bioprinting for tissue engineering and medical applications. However, COL1 is challenging to print layer-by-layer because it is a fluid solution that must be rapidly gelled and held in position during fabrication. To address this we developed Freeform Reversible Embedding of Suspended Hydrogels (FRESH), which extrudes (embeds) gelling fluids within a thermoreversible support bath that is removed after printing. Here we have improved the 3D bioprinting of COL1 using FRESH. First, since COL1 composition varies depending on its source, we show that our approach is able to utilize COL1 from rat tail and bovine skin. Second, we printed freestanding structures with defined infill architecture varying from 30% to 100% solid (monolithic). Third, we achieved manifold and perfusable vascular-like constructs and imaged them via micro CT to assess patency. Finally, we printed a scaled human heart model from MRI data and formed small features such as arteries and valves that were qualitatively similar to the 3D computer model. In summary, we have demonstrated that complex biological structures can be biofabricated directly from COL1 hydrogel using FRESH 3D printing.