(229ak) Cells Sense and Respond to the Surface Tension of Biomaterials

Cells physically interrogate their extracellular environment to inform decision making related to cell proliferation, differentiation, migration and other critical processes. In addition to its biochemical properties, the physical properties of the extracellular matrix, including its stiffness, are key inputs into signaling networks. Recent experiments have illustrated that solid surface tension can have a dominant role in the mechanical behavior of soft materials. Here we test whether cells are able to sense material surface tension and whether surface tension is a dominant physical cue that regulates cell response to soft biomaterials. We find that cells interacting with soft materials with appreciable surface tension primarily sense and respond to surface tension and not the bulk moduli of the materials. Our results are consistent with theory that predicts that solid surface tension can dominate over elasticity at cellular length scales. Even on very soft substrates (E=100 Pa), if the surface tension is appreciable, cells assemble robust adhesion structures, spread over large areas, and migrate efficiently. Remarkably, we find that cells can even spread and migrate on liquid biomaterials that have high surface tension. On these materials, cells migrate through a highly collective, swarming-type motility that is significantly faster than migration on solid biomaterials. Together, our results indicate that material surface tension is an important criteria for the design of biomaterials for cell growth and morphogenesis in tissue engineering.