Merel L. Janssen

Filamentous supramolecular polymers provide a modular synthetic platform that can emulate various extracellular matrix biopolymers in their structure and function. However, hydrogels based on their entangled one‐dimensional nanostructures are mechanically weak and challenged in replicating the properties of native tissues that surmount cyclic compressive loads. Inspired by the structural features of load‐bearing tissues such as cartilage that consist of water‐rich and interconnected biopolymer networks with distinct features, we explore the in situ photopolymerization of a secondary covalent network within a filamentous supramolecular material. The resulting connectable hybrid double network hydrogels show biomimetic cartilage‐like mechanical properties under dynamic loads, such as hydrostatic pressure generation and stress relaxation. We further exploit the biocompatible dithiolane‐ene light‐mediated crosslinking reaction to culture human primary articular chondrocytes in 3D within the materials under cyclic compressive loads. Their loading leads to significantly increased production of cartilaginous matrix proteins, sulfated‐glycosaminoglycans, fibronectin I and collagen II, particularly in the photocrosslinked domains. The enclosed hybrid supramolecular and covalent double network strategy with biocompatible light‐mediated crosslinking paves the way to expand the application space of filamentous supramolecular materials in 3D cell culture, providing facile access to compressive mechanical features such as hydrostatic pressure and stress relaxation essential for load‐bearing cell types.

Dynamic polymer materials are highly valued substrates for 3D cell culture due to their viscoelasticity, a time‐dependent mechanical property that can be tuned to resemble the energy dissipation of native tissues. Herein, we report the coupling of a cyclic thiosulfinate, mono‐S‐oxo‐4‐methyl asparagusic acid, to a 4‐arm PEG‐OH to prepare a disulfide‐based dynamic covalent hydrogel with the addition of 4‐arm PEG‐thiol. Ring opening of the cyclic thiosulfinate by nucleophilic substitution results in the rapid formation of a network showing a viscoelastic fluid‐like behaviour and relaxation rates modulated by thiol content through thiol‐disulfide exchange, whereas its viscoelastic behaviour upon application as a small molecule linear crosslinker is solid‐like. Further introduction of 4‐arm PEG‐vinylsulfone in the network yields a hydrogel with weeks‐long cell culture stability, permitting 3D culture of cell types that lack robust proliferation, such as human pluripotent stem cell‐derived cardiomyocytes (hPSC‐CMs). These cells display native behaviours such as cell elongation and spontaneous beating as a function of the hydrogel's mechanical properties. We demonstrate that the mode of dynamic cyclic thiosulfinate crosslinker presentation within the network can result in different stress relaxation profiles, opening the door to model tissues with disparate mechanics in 3D cell culture.

Dynamic polymer materials are highly valued substrates for 3D cell culture due to their viscoelasticity, a time‐dependent mechanical property that can be tuned to resemble the energy dissipation of native tissues. Herein, we report the coupling of a cyclic thiosulfinate, mono‐S‐oxo‐4‐methyl asparagusic acid, to a 4‐arm PEG‐OH to prepare a disulfide‐based dynamic covalent hydrogel with the addition of 4‐arm PEG‐thiol. Ring opening of the cyclic thiosulfinate by nucleophilic substitution results in the rapid formation of a network showing a viscoelastic fluid‐like behaviour and relaxation rates modulated by thiol content through thiol‐disulfide exchange, whereas its viscoelastic behaviour upon application as a small molecule linear crosslinker is solid‐like. Further introduction of 4‐arm PEG‐vinylsulfone in the network yields a hydrogel with weeks‐long cell culture stability, permitting 3D culture of cell types that lack robust proliferation, such as human pluripotent stem cell‐derived cardiomyocytes (hPSC‐CMs). These cells display native behaviours such as cell elongation and spontaneous beating as a function of the hydrogel's mechanical properties. We demonstrate that the mode of dynamic cyclic thiosulfinate crosslinker presentation within the network can result in different stress relaxation profiles, opening the door to model tissues with disparate mechanics in 3D cell culture.