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We design and build biomimetic emulsions as minimal, quantitative model systems to dissect the mechanical principles governing cell–cell adhesion and tissue organization. By coating droplets with cell adhesion proteins such as E-cadherin, we create biomimetic tissues that isolate the physical role of force in cell-cell adhesion. We established a unified physical picture in which mechanics and cooperativity play an important role in biological adhesion.
We quantitatively determine the role of the cadherin ectodomain in mechanosensing. To this end, we devise an E-cadherin-coated emulsion system, in which droplet surface tension is balanced by protein binding strength to give rise to stable areas of adhesion. Removing the lateral cis interaction with a ‘‘cis mutant’’ shifts recruitment to higher surface densities leading to denser, yet weaker adhesions.
Nagendra, et al., Push-pull mechanics of E-cadherin ectodomains in biomimetic adhesions, Biophys. J. 122, 2023.
The visualization of a three-dimensional assembly of lipid droplets, functionalized with extracellular E-cadherin domains, reveals a hierarchy of homophilic interactions. First, the high interfacial tension of droplets facilitates trans cadherin-cadherin adhesion, which is strong enough to stabilize looser than random close packing configurations. Second, The addition of clustering agents, such as calcium or chelating ligands, favor the lateral cis adhesion of the already bound cadherin pairs.
Pontani, et al., Cis and Trans Cooperativity of E-Cadherin Mediates Adhesion in Biomimetic Lipid Droplets, Biophys. J. 110, 2016.
We study the phase behavior of immiscible mixtures of phospholipids and cholesterol at the interface of oil-in-water emulsions, which governs the surface morphology of patchy droplets. Emulsification with lipid mixtures leads to domain formation with a variety of shapes, such as spots, disordered stripes, hemispheres and rings.
Pontani, et al., Immiscible lipids control the morphology of patchy emulsions, Soft Matter 9, 2013.
Particulate packings in 3D are used to study the effects of compression and polydispersity on the geometry of the tiling in these systems. We find that the dependence of the neighbor number on cell size is quasilinear in the monodisperse case and becomes nonlinear above a threshold polydispersity, independent of the method of creation of the tiling.
Newhall, et al., Size-Topology Relations in Packings of Grains, Emulsions, Foams, and Biological Cells, Phys. Rev. Lett. 108, 2012.
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