Mapping single cell mechanics as a function of environment geometry using Brillouin microscopy and optical tweezers microrheology

Cancer cells encounter a range of mechanical challenges as they invade secondary organs. Mechanical phenotype of the cell is a critical parameter that determines successful invasion and survival following deformations due to confinement, and physical forces. Here, we quantify the diversity of the mechanical states of live cells in biomimetic systems that recapitulate in vivo 2D and 3D environments. To measure cell mechanics on a sub-micrometer scale we use Brillouin microscopy (~GHz) and broadband frequency optical tweezer microrheology (3Hz-15kHz). We assessed the mechanical phenotype of U87 cell line in 2D and 3D environments where we tuned the substrate stiffness, dimensionality (3D versus 2D), and presence of fibrillar topography in 3D. We confirmed that the cells have higher Brillouin shift on rigid substrates, which is indicative of increased intracellular stiffness. Interestingly, cells embedded inside 3D hydrogels showed similar mechanical properties as the cells cultured on top of thick 2D hydrogels. We observed this using both Brillouin microscopy, and optical tweezers (G’=39±11Pa, G’’=25±7Pa at 19Hz). These findings are exciting as they confirm a correlation between two different measurement techniques that probe mechanics of live cells at different timescales.