Confinement Induces Morphological and Topological Transitions in Multivesicles.

The study of self-assembly in confined spaces has gained significant attention among amphiphilic superstructures and colloidal design. The additional complexity introduced by interactions between contents and their containers, along with the effects of shape and lipid mixing, makes multivesicular bodies an interesting subject of study. Despite its promising applications in biomedicine, such as drug delivery and biomimetic materials, much remains unexplored. Here we investigate the effects of confinement on vesicles with varying lipid tail lengths. We first analyze the morphological changes of single spherical vesicles undergoing dehydration, which leads to a prolate-to-oblate transition. Our findings reveal that reductions in water content induce changes of shape while minimally affecting the surface area needed to maintain the hydration layer of lipid phosphate groups. Additionally, using extensive coarse-grained molecular dynamics simulations, we explore how vesicles confined within other vesicles evolve through topological changes into unexpected structures, mainly influenced by the lipid hydrocarbon lengths. Our results highlight the interplay between confinement, curvature-induced lipid sorting, and lipid-mixing entropy, leading to exquisitely self-assembled superstructures.