Membrane Tension–Mediated Growth of Liposomes

Abstract

Recent years have seen a tremendous interest in the bottom‐up reconstitution of minimal biomolecular systems, with the ultimate aim of creating an autonomous synthetic cell. One of the universal features of living systems is cell growth, where the cell membrane expands through the incorporation of newly synthesized lipid molecules. Here, the gradual tension‐mediated growth of cell‐sized (≈10 µm) giant unilamellar vesicles (GUVs) is demonstrated, to which nanometer‐sized (≈30 nm) small unilamellar vesicles (SUVs) are provided, that act as a lipid source. By putting tension on the GUV membranes through a transmembrane osmotic pressure, SUV–GUV fusion events are promoted and substantial growth of the GUV is caused, even up to doubling its volume. Thus, experimental evidence is provided that membrane tension alone is sufficient to bring about membrane fusion and growth is demonstrated for both pure phospholipid liposomes and for hybrid vesicles with a mixture of phospholipids and fatty acids. The results show that growth of liposomes can be realized in a protein‐free minimal system, which may find useful applications in achieving autonomous synthetic cells that are capable of undergoing a continuous growth–division cycle.

Engineering bio-mimicking functional vesicles with multiple compartments for quantifying molecular transport

“…4 Moreover, vesicles can serve as an excellent scaffold to study biological processes occurring at a membrane interface. [5][6][7] To study specic membranebiophysical properties, controlling the lipid-composition in giant vesicles under dened external conditions is extremely crucial and yet challenging. 2,8 Several solvent-displacement techniques have been used for giant vesicle preparation with a variety of complex lipids under physiological salt conditions.…”

Protein-free division of giant unilamellar vesicles controlled by enzymatic activity

“…Most remarkably, we show that GUV division can be regulated autonomously by metabolic activity. Growth of GUVs, on the other hand, has already been demonstrated previously [39,40,41] -making the implementation of multiple growth and division cycles an exciting next goal. This could, for instance, be realized by targeted fusion [42] of SUVs composed of the opposite lipid type.…”

Fusing Artificial Cell Compartments and Lipid Domains Using Optical Traps: A Tool to Modulate Membrane Composition and Phase Behaviour

“…The use of optical traps to select, manipulate, and fuse user-defined vesicles with another opens the possibility of dynamically and controllably modulating membrane composition by introducing new lipid cargo. Although fusion between Small Unilamellar Vesicles (LUVs; c. 100 nm diameter) and GUVs has been used to introduce protein machinery into membranes [23] and induce GUV growth [13], this method cannot be used to controllably alter the lipid composition due to the lack of control of the number of fusion events. In principle, laser-assisted GUV fusion offers precise spatial and temporal control which bypasses this limitation.…”

“…Bioengineers are increasingly exploiting this phenomenon, with synthetic membrane fusion events playing key roles in liposomal drug delivery [5], cell-like microreactors [6,7], cell transfection [8], the creation of cell hybrids for vaccine generation [9], and for therapeutic applications [10,11]. Membrane fusion is also being deployed in synthetic biology, to initiate protein synthesis in artificial cells through the delivery of genetic material [12] and in the creation of artificial cells that are capable of growing over time by subsuming new membrane material [13].…”