Ice Templated PEG-Alginate Double-Network Cryogels with Tunable Mechanics and Degradation for Soft Tissue Engineering

Scaffolds designed for mechanically demanding soft tissue engineering applications should integrate mechanical support, efficient mass transfer, and good cellular compatibility. This work presents a one-pot method based on "radical-free click chemistry + carbodiimide coupling" to produce a double-network (DN) PEG-alginate cryogel. The PEG network is formed by a Michael addition reaction between thiol-based crosslinker and 8-arm PEG-acrylate. The second network is covalently crosslinked through EDC/NHS-mediated coupling of carboxyl groups in alginate and adipic acid dihydrazide (AAD). The subsequent freezing and gelation of the gel precursor at sub-zero temperatures results in an ice templated cryogel with an interconnected macroporous network. These cryogels demonstrate high elasticity, compressive modulus and rapid swelling equilibrium in aqueous environments, as well as controlled degradation under physiological conditions. Compared to the classical Ca²⁺ ion crosslinking systems, the covalent linking of the alginate in the double-network cryogel shows advantages in mechanical and structural stability. In addition, it is cell-compatible and allows culture of mesenchymal stem cells (MSCs) with homogeneous infiltration. Furthermore, the double-network cryogels supports chondrogenic differentiation of MSCs upon treatment with chondrogenic media or macrophage-conditioned media for a short period of time. These results indicate that crosslinking chemistry and polymer composition can be used to modulate the balance between mechanical performance and degradation behavior, while maintaining cytocompatibility and an interconnected macroporous network, thereby providing a scaffold design strategy for applications that require coordinated mechanical support and mass transfer, such as cartilage-related tissue engineering.