Picosecond ultrasounds as elasticity probes in neuron-like cells models

Perturbation of tissue rigidity is associated with different types of pathology. However, it is sometimes difficult to conclude if this change in stiffness of cells or tissue is the effect or the source of the pathologies. This is why the characterization of the mechanical properties of cells is essential to understand their behavior during mitosis, apoptosis, adhesion, mobility and disease development. However, the complexity of the inner cell composition and the intricate meshwork formed by molecular mediators of the transmembrane cell-substrate interactions requires non-invasive techniques to probe and quantify local mechanical properties of cells, including modulus of elasticity, viscoelastic properties, adhesion, and forces created at the single-cell scale. Several recent reviews describe tools used to study cell mechanics and to apply forces on them. Acoustic waves generated by lasers provide a very adequate tool for probing the mechanical properties of biological cells or tissues in a non-contact, non-invasive configuration. We report on detection of Brillouin (BO) signature used for mapping elastic properties in single neuron-like cells. To our knowledge, this is the first time this technique is used on this type of cells, in which the regeneration processes are closely related to cell elasticity. The elasticity contrasts thus revealed between the nucleus and the cytoskeleton in the reticulate cells also obviously exist in living cells for which the study is more subtle given the very specific conditions necessary for their maintenance . The frequencies and the lifetimes of the BOs are mapped across the cell using Pearson correlation method. The influence of hydration, i.e. a more biologically relevant conditions, on the cell elasticity is investigated. Finally a correlative microscopy coupling elastic mapping, atomic force microscopy and fluorescence will be presented in motoneuron single cells.