Modulation of phase separation at the micron scale and nanoscale in giant polymer/lipid hybrid unilamellar vesicles (GHUVs)

Abstract

Phase separation in giant polymer/lipid hybrid unilamellar vesicles (GHUVs) has been described over the last few years. However there is still a lack of understanding on the physical and molecular factors governing the phase separation in such systems. Among these parameters it has been suggested that in analogy to multicomponent lipid vesicles hydrophobic mismatches as well as lipid fluidity play a role. In this work, we aim to map a global picture of phase separation and domain formation in the membrane of GHUVs by using various copolymers based on poly(dimethylsiloxane) (PDMS) and poly(ethylene glycol) (PEO) with different architectures (grafted, triblock) and molar masses, combined with phospholipids in the fluid (POPC) or gel state (DPPC) at room temperature. From confocal imaging and fluorescence lifetime imaging microscopy (FLIM) techniques, the phase separation into either micro- or nano-domains within GHUVs was studied. In particular, our systematic studies demonstrate that in addition to the lipid/polymer fraction or the lipid physical state, important factors such as line tension at lipid polymer/lipid boundaries can be finely modulated by the molar mass and the architecture of the copolymer and lead to the formation of stable lipid domains with different sizes and morphologies in such GHUVs.

Barcoding Biological Reactions with DNA‐Functionalized Vesicles

“…Domains have been recapitulated and characterized in both lipid and polymer systems. [43,[51][52][53][54][55][56][57][58] Understanding how to harness biophysical properties of bilayer membranes to expand their functionality beyond containment alone is an important step in the design of artificial cellular systems. Cellular plasma membranes are heterogeneous and contain av ariety of distinct regions with varying biophysical properties that we can draw from to design such systems.T hese physical features of the membrane can influence biochemical events by mediating fusion or increasing the local concentration of membrane proteins to aid targeting and adhesion.…”

Barcoding biological reactions with DNA-functionalized vesicles

“…[43,[51][52][53][54][55][56][57][58] Understanding how to harness biophysical properties of bilayer membranes to expand their functionality beyond containment alone is an important step in the design of artificial cellular systems. Domains have been recapitulated and characterized in both lipid and polymer systems.…”

Hybrid vesicles from lipids and block copolymers: Phase behavior from the micro- to the nano-scale

“…POPC gives rise to homogeneous giant vesicles in a restricted range of compositions [12] for PBD based copolymers, while for PDMS based triblock copolymers, vesicles always form. On the other hand, DPPC always form inhomogeneous systems with domains independently of the hydrophobic mismatch in the case of PDMS copolymers [11]. Homogeneous GUVs (Giant Unilamellar Vesicles) are also observed for PIB block copolymers in the lipid-rich and polymerrich regions (below 18 mol% and above 30 mol% DPPC), while phase separation occurs only for intermediate compositions [13].…”

“…In this case, it was demonstrated that the hydrophobic mismatch is an important parameter for lipids in the fluid phase. Indeed, when the block copolymer molecular weight increases, homogeneous vesicles form in a larger range of compositions in the region of low lipid content [5,11]. At higher lipid content phase-separated vesicles form, and budding is observed; phase-separated vesicles are not stable and budding degenerates in vesicle fission for copolymers of higher molecular weights.…”

“…In the case of PDMS based triblock copolymers [7], for example, the copolymer with the highest mismatch induced the largest effect on permeability and melting temperature of hybrid DPPC-polymer vesicles, but less impact on the vesicles' size. Very recently Dao et al [11] underlined the need for more detailed investigations on the morphology of the nanostructures, the distributions of the components in the bilayers in order to understand the important parameters (i.e. chemical nature, curvature and hydrophobic mismatch) involved.…”