Bioprinting a Multifunctional Bioink to Engineer Clickable 3D Cellular Niches with Tunable Matrix Microenvironmental Cues.

The properties of the surrounding cell environment are major determinants of cell response in 3D. However, the ability to unravel how these cues dictate the biological function in bioprinted constructs is limited by the lack of extracellular matrix (ECM)-mimetic bioinks with fully controllable properties. In this study, a multifunctional bioink that uniquely combines the independent control over the biochemical and biophysical cues that regulate cell fate with the bioorthogonal nature of thiol-norbornene photoclick chemistry is designed for the extrusion bioprinting of bioinspired 3D cellular niches with tunable properties. The bioink rheology is controlled by ionic gelation, being dependent on both the type and content of divalent ions (calcium and barium), while the mechanical and biochemical properties of hydrogels are tailored via a post printing thiol-ene reaction. Bioprinted cell-adhesive and protease-degradable hydrogels modulate cell proliferation and ECM deposition in a matrix-stiffness dependent manner over 14 days of culture regardless of cell spreading, demonstrating the ability to probe the effect of matrix cues on cell response. This bioink can be used as a versatile platform where building blocks can be rationally combined for the bioprinting of functional cell- and tissue-specific constructs with controlled cellular behavior.