3D Bioprinting of Spatially Heterogeneous Collagen Constructs for Cartilage Tissue Engineering.

3D printing of biological tissues has been of increasing interest to the biomaterials community in part because of its potential to produce spatially heterogeneous constructs. Such technology is particularly promising for orthopedic applications, which require the generation of complex geometries to match patient anatomy and complex microstructures to produce spatial heterogeneity and anisotropy. Prior research has demonstrated the capacity to create precisely shaped 3D printed constructs using biocompatible alginate hydrogels. However, alginate is extremely compliant and brittle, and high-density collagen hydrogels could be a preferable option for load-bearing applications. This research focused on developing and evaluating a method of printing soft tissue implants with high-density collagen hydrogels using a commercially available 3D printer, modified for tissue-engineering purposes. The tissue constructs, seeded with primary meniscal fibrochondrocytes, were evaluated using measures of geometric fidelity, cell viability, mechanical properties, and fiber microstructure. The constructs were found to be mechanically stable and were able to support and maintain cell growth. Furthermore, heterogeneous 3D-printed constructs were generated, consisting of discrete domains with distinct mechanical properties.