Institut des
NanoSciences de Paris
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Mechanical properties of biomimetic emulsions

We developed novel tissue-mimetic systems to understand the passive mechanical response of biological tissues, thus transferring a biological question to a soft matter framework. Indeed just as liposomes mimic single cells, densely packed emulsion droplets can be used to mimic the mechanical and adhesive properties of biological tissues. We use a biomimetic emulsion in which the droplets reproduce the minimal mechanical properties of cells in tissues : the droplets are stabilized by phospholipids to mimic the cellular membrane ; their surface is functionalized with adhesive proteins to reproduce cell-cell surface interactions in tissues. The versatility of this system allows one to tune the droplet interactions by using a wide range of adhesive molecules on the droplets surface, such as biotin-streptavidin, DNA strands or immiscible lipid mixtures leading to patchy domains. This control over the energetics of the interactions also paves the way for the programmable self-assembly of complex mesostructures. In addition to this we make transparent emulsions by index matching the oil phase and the aqueous continuous phase. This allows us to image the 3D structure of the emulsions through confocal microscopy in order to identify the topology of the packing in 3D as well as the adhesive interactions between the droplets. Therefore this system is suitable for the study of stress propagation in the droplet packing in response to mechanical perturbations, such as those observed during development. Studying the elasto-plastic response of those systems in response to local perturbations will provide a direct link between the force networks, the adhesion strength and the observed collective movements (associated with topology changes and adhesion reorganizations) in tissues.

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3D reconstitution of a droplet packing imaged through confocal microscopy. Scale = 100x100x100um^3
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Image analysis : (A) The adhesion patches between the droplets are visualized in bright yellow throughout the 3D packing. (B) the deformation between contacting droplets is derived from the geometrical overlap between the spheres that are fitted around each droplet. rp is the adhesion patch radius, rd is the deformation area radius.