Laboratoire Matière et Systèmes Complexes

Vicard Du

Equipe biofluidique

Magnetic embryonic stem cells : new tools to control embryoid bodies differentiation

One of the questions of interest in embryogenesis is to understand the differentiation orientation of the embryonic stem cell (ESC) according to their environment. While more and more molecular actors of differentiation are being identified, at the opposite, the roles of physical signals perceived by the cells or the cell-cell spatial organization are little explored. Original tools are nevertheless being developed to study mechanical aspects like mold to organize aggregate shape, stretching machine for mechanical stimulus, micropillar environment to measure cell forces…

The aim of our research is to understand the influence of physical constraint on ESC differentiation. For such purpose, we magnetize ESC by magnetic nanoparticles internalization. First we studied the impact of nanoparticle internalization on the pluripotence genes Nanog, Sox2, Oct4. Second we investigated the magnetic compaction method for the differentiation of cell aggregate called embryoid bodies by screening a large range of genes specific to different cell types. The results demonstrate that our magnetic technique gives a very similar gene expression than when using the standard pending drop method. The advantages of the magnetic compaction to differentiate embryoid bodies are the facility to use, the gain in time, and to avoid some transfer steps. We are currently developing a modulated magnetic fields that will able us to shape a magnetic cellular aggregate in 3D which we can deform continually or cyclically at the cellular and tissue scale. The idea is to analyze the differentiation of these cells in function of the frequency and the intensity of these physical constraints.

The project on the one hand is fundamental, to understand the orientation of the differentiation through the compaction and stretching phenomena, and on the other hand it is applicative, to direct the ESC differentiation in specialized cells, and to manipulate a tissue in 3D with magnetic tweezers.

Matthieu Labousse

Equipe DSHE

Bouncing droplet in a central force, a surprising case of self-organisation

M. Labousse, S. Perrard, Y. Couder, E. Fort

A millimetric droplet may bounce inde-nitely on a vertically vibrating fluid bath ; moreover, above a critical vibrational acceleration, the bouncing state is destabilized and gives way to a walking state in which the drop is propelled forward by its own guiding wave -eld. This macroscopic wave-particle association exhibits fascinating quantum-like behaviours that are strongly experimentally supported, e.g. diffraction, double slits, Landau levels, tunnel effect, Zeeman splitting, cavities. A new step has been taken in the understanding of this system by applying a harmonic potential to a ferrofluidic drop. Depending of the interaction with its past -field, a transition from classical to quantized behaviours is observed and provided by a strongly non-linear dynamics. We will briefly report the experimental and simulation results of this dual system . A double quantization of energy and angular momentum is observed, with selection rules surprisingly similar to the 2D quantum harmonic potential. This apparent selection rules will be interpreted as a self-organization sustained by the multiple time scales of the dynamics.