Novel, high-throughput collagen-based bioprinting for tissue engineering.

Abstract

Bioprinting is an emerging biofabrication technology with increasingly critical applications in tissue engineering, drug screening, and regenerative medicine. Collagen type I, a prevalent extracellular matrix (ECM) scaffolding protein, is one of the most popular biomaterials for tissue models and bioprinting scaffolds. However, mimicking physiological collagen architectures and producing defined geometries are hindered by the limited tunability of conventional in vitro gelation techniques. Previously, the macromolecular crowding effect was found to tune collagen properties. Here, we harness the crowding effect to develop a high-throughput, tunable method for creating collagen tissues with controllable geometries, including disks, bundles, strips, and hand-drawn shapes. Compared to conventionally gelled collagen, crowded collagen structures better recapitulate the scale and density of in vivo collagen, forming within seconds to minutes as opposed to hours. Using crowded collagen as a scaffolding material, we bioprinted mesenchymal stem cells, human liver carcinoma cells, and endothelial cells into microtissues that showed high tissue integrity and longevity. We quantified cell contraction and observed the self-organization of physiologically relevant structures such as microvasculature. Finally, we demonstrate the modular assembly of crowded collagen microtissues into larger-scale tissue structures. Our study illustrates new methods for bioprinting and scaffolding while showcasing new ways to study tissue organization.