Polyacrylamide-Based Hydrogel with Biocompatibility and Tunable Stiffness for Three-Dimensional Cell Culture

Three-dimensional (3D) culture of cells has gained increasing popularity because of its enhanced physiological relevance and more accurate representation of in vivo tissues. Matrigel, alginate, hyaluronic acid, and collagen are biocompatible 3D culture platforms with cell biofunctions, while it is difficult to decouple the biofunctions with mechanical properties. Polyacrylamide (PAAm) is a biocompatible but biologically nonfunctional platform heavily used in 2D culture. However, the cytotoxicity of acrylamide (AAm) prevents the application of PAAm as a platform for the 3D culture. Here, through RAFT copolymerization of AAm with a primary amine-bearing functional monomer, followed by postpolymerization modification, we synthesized nontoxic, linear PAAm featuring either multithiol or multinorbornene groups, available in various chain lengths. PAAm networks were fabricated by photoinduced thiol-norbornene coupling. The resulting PAAm hydrogel was biocompatible and structurally homogeneous with highly tunable and reproducible mechanical properties. PAAm hydrogels supported the 3D culture of human umbilical vein endothelial cells (HUVECs), where a higher adhesive ligand density promoted the viability of HUVECs. Furthermore, in combination with Matrigel, the PAAm hydrogel was used in the 3D culture of intestinal organoids, demonstrating that a lower mechanical strength was favorable. In summary, this report paves the way for the use of PAAm hydrogels in 3D culture, which is especially appealing for the decoupling of biological functions and mechanical properties.