Viscoelastic Cell Microenvironment: Hydrogel‐Based Strategy for Recapitulating Dynamic ECM Mechanics

The native extracellular matrix (ECM) generally exhibits dynamic mechanical properties and displays time‐dependent responses to deformation or mechanical loading, in terms of viscoelastic behaviors (e.g., stress relaxation and creep). Viscoelasticity of the ECM plays a critical role in development, homeostasis, and tissue regeneration, and its implication in disease progression has also been recognized recently. Hydrogels with tunable viscoelastic properties hold a great promise to recapitulate such time‐dependent mechanics found in native ECM, which have been recently used to regulate cell behavior and guide cell fate. Here the importance of tissue viscoelasticity is first highlighted, the molecular mechanisms of hydrogel viscoelasticity are summarized, and characterization techniques used at the macroscale and microscale are reviewed. Then, recent advances in developing novel hydrogels with tunable viscoelasticity through varying crosslinking strategies, engineering of viscoelastic cell microenvironment and its substantial effects on cell behavior and fate are described, and the underlying mechanobiology mechanisms are subsequently discussed. Finally, the ongoing challenges and future perspectives on the design and modulation of viscoelastic hydrogels and the mechanobiology mechanisms on cellular responses to viscoelastic cell microenvironment are proposed.