Delamination and restructuring inside multilamellar lipid vesicles by a polycation: formation of multi-compartment vesicles.

We describe experiments and analysis of delamination and reformation of multilamellar vesicles triggered by their interaction with highly charged polycations in the exterior solution. Above a threshold polymer concentration, the vesicles reform their multilamellar outer membrane into close-packed interior membrane compartments. The process leads to a vesicle with a hierarchically ordered superstructure, i.e., vesicular superparticles. Using giant multilamellar vesicles, we report time-lapse observations of the formation process and also of the breakup process after the polymer is diluted at constant osmotic stress. We show the results of a range of polymer molecular weights and concentrations. We present a simple model that predicts conditions of delamination owing to a competition between electrostatic repulsion among the polymers and the bending elasticity of the membranes. The results pave the way to a new kind of response mechanism in multilamellar vesicles that might lead to soft materials that can change their stiffness or topology on demand.