Dictated cell adhesion and migration using microfluidic-controlled synthetic hydrogels exhibiting programmable viscoelasticities

Mechanosensing interactions between the extracellular matrix (ECM) and the intracellular cytoskeleton are fundamental to cellular functions such as motility, proliferation, and adhesion, driven by the dynamic, bidirectional, tension-regulated maturation of focal adhesion (FA) sites. We demonstrate that native mechanosensing interactions and their downstream functions are precisely controlled using synthetic hydrogels. We introduce a microfluidic-assisted synthesis of imine-crosslinked hyaluronic acid-gelatin copolymer hydrogels (HAG), enabling controlled, predefined gradient viscoelasticity. Specifically, three native tissues (muscle, epidermis, and cartilage)-mimicking HAG hydrogels were prepared, matching their effective Young's modulus (Ymod) and stress relaxation time (τ_1/2). Enhanced cell spreading and directional cell migration are observed, with a preference for substrates with tissue-matching viscoelasticity. These mechanosensing reactions are confirmed by traction force microscopy, revealing a tight correlation between native tissue mechano-properties and the hydrogel viscoelastic parameters. We demonstrate that the signaling efficacies of the FAK and associated YAP/TAZ pathways, central regulators of FA formation and cell migration, are tuned by substrate tissue-matching viscoelasticity. We implement these preprogrammed viscoelastic gradient hydrogels as spatiotemporal cell-separation matrices, enabling viscoelasticity-driven migration of binary cell mixtures. This work provides a potent platform for studying cell-material interactions, offering significant potential applications in tissue engineering, immunotherapy, and regenerative medicine.