Hybrid active matter: particles and cellular aggregates*

We investigate the collective migration of cell on adhesive substrates, using 3D cellular aggregates as a model system. Aggregates spread by expanding outwards a cell monolayer, which may dewet, causing the aggregates to move as “Giant Keratocytes”. We interpret this motion by a symmetry-breaking of cell polarity in analogy to active droplets.
We then describe mixture of dead and living matter and how microparticles play with cells. The size of the particles is varied from nanometers to few microns. Nanoparticles (size 20nm) can be used as a glue “nanostickers” to stick cells together and have important applications for cellular therapy and cancer treatment. Micro-particles MiPs (size ≈ micron) are used to study the spreading of cell aggregates on substrates decorated with MiPs. A cell monolayer expands around the aggregate. Cells at the periphery uptake the microparticles “gluttonous cells” by phagocytosis ,forming an aureole of cells full of particles. Macro-particles MaPs (size ≈10 microns) are to big to be eaten and they are put into active motion” dancing” . We study also phase separations in hybrid particles -cells aggregate versus beads volume fraction.