Increased efficiency of charge-mediated fusion in polymer/lipid hybrid membranes

Due to their augmented properties, biomimetic polymer/lipid hybrid compartments are a promising substitute for natural liposomes in multiple applications, but the proteinfree fusion of those semisynthetic membranes is unexplored to date. Here, we study the charge-mediated fusion of hybrid vesicles composed of poly(dimethylsiloxane)graft-poly(ethylene oxide) and different lipids and analyze the process by size distribution and the mixing of membrane species at mu m and nano scales. Remarkably, the membrane mixing of oppositely charged hybrids surpasses by far the degree in liposomes, which we correlate with properties like membrane disorder, rigidity, and ability of amphiphiles for flip-flop. Furthermore, we employ the integration of two respiratory proteins as a functional content mixing assay for different membrane compositions. This reveals that fusion is also attainable with neutral and cationic hybrids and that the charge is not the sole determinant of the final adenosine triphosphate synthesis rate, substantiating the importance of reconstitution environment. Finally, we employ this fusion strategy for the delivery of membrane proteins to giant unilamellar vesicles as a way to automate the assembly of synthetic cells.

Automated summary

Biomimetic polymer/lipid hybrid compartments have great potential as substitutes for natural liposomes. This study explores the protein-free fusion of these semisynthetic membranes and finds that the membrane mixing of oppositely charged hybrids exceeds that of liposomes. The charge is not the sole determinant of the final adenosine triphosphate synthesis rate, and the fusion strategy can be used for the delivery of membrane proteins and the automation of synthetic cell assembly.