Soft hydrogels are very promising biomaterials for various applications in tissue engineering and regenerative medicine. Compared to materials made with natural constituents, synthetic hydrogels offer a fine control of composition and functionalization with adhesive ligands, along with tunable mechanical properties, as it is crucial for most investigations in mechanotransduction. While numerous studies have explored how substrate stiffness E influences cell behavior, the role of surface tension σ in guiding cell motility remains unexplored. Due to the elastocapillarity phenomenon, σ of soft materials can dominate their bulk stiffness E and thus regulate cellular response. To address this complex issue of mechanosensing, we proposed a new polymer-based hydrogel that provides a fine control of the surface tension. This hydrogel is composed of polyethylene glycol (PEG) elastic units, cross-linked with poly-L-lysine dendrigrafts molecules (DGL). The stiffness and interfacial mechanical properties of this hydrogel are controlled by adjusting the DGL/PEG ratio and mechanically characterized with optical tweezers. This powerful technique allows active microrheology and surface micro-indentation to assess E and σ with the same setup. The impact of σ in mechanotransduction was investigated through 2D migration of fibroblasts (WPMY-1 and CAF-2 cells) on fibronectin-coated hydrogels. Single-cell trajectories were tracked using epi-fluorescence imaging, and direction and speed autocorrelations were computed and analyzed using the “stick-slip” model. We clearly demonstrated that fibroblasts adopt a directional persistence migration when the surface tension σ increases.
Faour et al. (Sun,) studied this question.