Formation of Asymmetric and Symmetric Hybrid Membranes of Lipids and Triblock Copolymers

Abstract

Hybrid membranes formed by co-assembly of AxByAx (hydrophilic-hydrophobic-hydrophilic) triblock copolymers into lipid bilayers are investigated by dissipative particle dynamics. Homogeneous hybrid membranes are developed as lipids and polymers are fully compatible. The polymer conformations can be simply classified into bridge- and loop-structures in the membranes. It is interesting to find that the long-time fraction of loop-conformation ( f L ) of copolymers in the membrane depends significantly on the hydrophilic block length (x). As x is small, an equilibrium f L * always results irrespective of the initial conformation distribution and its value depends on the hydrophobic block length (y). For large x, f L tends to be time-invariant because polymers are kinetically trapped in their initial structures. Our findings reveal that only symmetric hybrid membranes are formed for small x, while membranes with stable asymmetric leaflets can be constructed with large x. The effects of block lengths on the polymer conformations, such as transverse and lateral spans ( d ⊥ and d ‖ ) of bridge- and loop-conformations, are discussed as well.

Membrane reinforcement in giant hybrid polymer lipid vesicles achieved by controlling the polymer architecture

“…Pure bilayer conformation is expected for a diblock copolymer whereas a mixture of extended and loop conformation is expected for a triblock copolymer. 38,39 The GHUV membrane from diblock copolymers did not show any sign of nanodomains segregation and merging into micrometric domains, as described for triblock copolymers based GHUV.…”

Polymer–Lipid Hybrid Materials

“…This stretches the BCP penetrating through the membrane and places each PEO block in the outer and inner leaflet. 96,97 Interestingly, for the graft copolymer−lipid GHUVs (PDMS 26 -g-(PEO 12 ) 2 /POPC), phase separation into microscopic lipid domains starts from ≥22 wt % lipids (50 mol %), 47 while for the triblock copolymer−lipid GHUVs (PEO 8 -b-PDMS 22 -b-PEO 8 /POPC), microscale phase separation occurs at 16 wt % lipid composition. 67 Triblock copolymer−POPC GHUVs were stable for a few days, but the graft copolymer− POPC GHUVs undergo budding and fission phenomena in the first few hours after preparation via electroformation.…”

Perforated Vesicles of ABA Triblock Copolymers with ON/OFF-Switchable Nanopores

“…A spherical vesicle can be formed by fully flexible A 3 B 14 A 3 triblock copolymers ( k θ = 0). The polymer layer enclosing a water core consists of both bridge- and loop-conformations and can be regarded as a mixed monolayer/bilayer structure. − As mentioned, the loop-conformation (U-shape) depicts both hydrophilic ends of a copolymer appearing on the same side of the membrane, while the bridge-conformation (I-shape) represents that the two A-blocks are on the opposite sides. While the hydrophilic A-blocks prefer to be exposed to the water phase, the hydrophobic B-blocks tend to be sequestered from water by A-blocks.…”

“…DPD is useful in acquiring microscopic insights into the physical properties associated with assembled aggregates in solution, which are observed in experiments . In fact, the morphology of assemblies formed by block copolymers have been extensively studied by DPD. − We demonstrate that perforated vesicles can be formed simply by ABA triblock copolymers as long as the hydrophobic B-blocks possess semi-rigidity. In fact, the vesicle/membrane properties vary significantly with the inflexibility of the B-block and its effects will be examined thoroughly.…”