Fig. 1

Controlled formation of membraneless coacervates in liposomes. a A conceptual sketch showing controlled condensation within a liposome. By inserting bilayer-spanning protein pores, one can allow passive transport of small molecules, leading to the formation of a coacervate. Such a coacervate-in-liposome hybrid system can also be used as a scaffold for a synthetic cell, where the liposome represents the primary compartment (a cell), while the coacervate represents a sub-compartment (an organelle). b Side-view schematic (not to scale) of the experimental set-up. Liposomes encapsulating one of the coacervate component (C₁) or an enzyme catalyzing the production of C₁ are generated using OLA. The presence of high-density molecules, such as dextran, efficiently settles them at the bottom of the collection well, while the waste products (1-octanol droplets) float to the top. The other coacervate component, C₂, can already be present in the chamber or can be added later to induce coacervation. c A fluorescence image showing monodisperse liposomes settled at the bottom of the well. The red boundary indicates the lipid bilayer while the green lumen shows encapsulated FITC-pLL molecules. d A fluorescence image showing coacervates-in-liposomes. Transport of ATP through α-hemolysin pores led to a single pLL/ATP coacervate within each vesicle. e A composite image showing the colocalization of FITC-pLL (green) and cy5-ATP (blue), forming a coacervate within the liposome (red). The slight offset between pLL and ATP fluorescence is due to the diffusion of the coacervate between capturing of the images. f Turbidity plot showing that the threshold ATP concentration to commence coacervation is about 6 mM. Absorbance of three independent samples was measured (nine measurements per sample). g Dependence of coacervate size on the amount of pLL molecules encapsulated inside the liposome (n ≥ 73 for each data point). h Representative images of coacervates of different sizes formed within liposomes with different pLL concentrations. i Dependence of coacervate volume on pLL concentration. The coacervate volume is seen to scale approximately linearly (R² = 0.78) with the pLL concentration. Error bars in (f, g, i) indicate standard deviations. Source data are provided as a Source Data file