Fusion‐Induced Growth of Biomimetic Polymersomes: Behavior of Poly(dimethylsiloxane)‐Poly(ethylene oxide) Vesicles in Saline Solutions Under High Agitation

Abstract

Giant unilamellar vesicles serve as membrane models and primitive mockups of natural cells. With respect to the latter use, amphiphilic polymers can be used to replace phospholipids in order to introduce certain favorable properties, ultimately allowing for the creation of truly synthetic cells. These new properties also enable the employment of new preparation procedures that are incompatible with the natural amphiphiles. Whereas the growth of lipid compartments to micrometer dimensions has been well established, growth of their synthetic analogs remains underexplored. Here, the influence of experimental parameters like salt type/concentration and magnitude of agitation on the fusion of nanometer‐sized vesicles made of poly(dimethylsiloxane)‐poly(ethylene oxide) graft copolymer (PDMS‐g‐PEO) is investigated in detail. To this end, dynamic light scattering, microscopy, and membrane mixing assays are employed, and the process at different time and length scales is analyzed. This optimized method is used as an easy tool to obtain giant vesicles, equipped with membrane and cytosolic biomachinery, in the presence of salts at physiological concentrations.

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

“…1 C ). Since PDMS- g -PEO membranes are slightly negative ( 21 ) and PE-Rho and PE-NBD further increase their negativity ( 37 , 38 ), we tested whether the intrinsic charge of the polymer would suffice for membrane mixing. This hypothesis was confirmed upon mixing the tagged polymersomes with nontagged hybrids containing 5 to 40 mol% cationic lipids, whereby the highest degree (about 20%) of membrane mixing was again at 10 mol% DOTAP loading ( SI Appendix , Fig.…”

“…In this respect, we recently succeeded in employing SNARE machinery for the fusion of hybrid vesicles made of phosphatidylcholine and poly(dimethylsiloxane)-graft-poly(ethylene oxide) (PDMS- g -PEO) ( 37 ). Meanwhile, we were unable to fuse these hybrids in the absence of fusogenic proteins; the agitation in salt solutions that induced the successful fusion of pure polymersomes caused only fission when lipids were present ( 38 ). To the best of our knowledge, no other attempts for protein-free fusion of mixed polymer/lipid vesicles have been made to date.…”

Synthetic Cells Revisited: Artificial Cell Construction Using Polymeric Building Blocks

“…Opposite to budding, mechanically activated fusion of nanometer‐sized vesicles made of poly(dimethylsiloxane)‐poly(ethylene oxide) graft copolymer (PDMS‐ g ‐PEO) with p‐GUVs under physiological salt conditions has been observed, which resulted in growth of the GUVs. [ 250 ] Hybrid vesicles made of the same polymer and oppositely charged lipids also underwent rapid charge‐mediated fusion. Importantly, bo3 oxidase reconstituted into small (<1 µm) cationic hybrid vesicles was efficiently transferred to the membrane of anionic hybrid GUVs trapped in microfluidic device by charge‐mediated fusion.…”

Hierarchical Structures in Macromolecule‐Assembled Synthetic Cells

“…There have been recent reports describing synthetic membrane fusion that was driven by temperature-induced conformation change and variation of membrane packing, [32] irradiationinduced changes in the polarity of isomerized azobenzene, [33] as well as polymerization-induced self-assembly and ultrasound treatment. [34][35][36] Organic and inorganic molecules, as well as cognate and non-cognate molecules can hybridize together via membrane fusion. [27] The co-assembly of Janus dendrimersomes with the components of the bacterial membrane is an example of this phenomenon.…”