Mixing, Diffusion, and Percolation in Binary Supported Membranes Containing Mixtures of Lipids and Amphiphilic Block Copolymers

Abstract

Substrate-mediated fusion of small polymersomes, derived from mixtures of lipids and amphiphilic block copolymers, produces hybrid, supported planar bilayers at hydrophilic surfaces, monolayers at hydrophobic surfaces, and binary monolayer/bilayer patterns at amphiphilic surfaces, directly responding to local measures of (and variations in) surface free energy. Despite the large thickness mismatch in their hydrophobic cores, the hybrid membranes do not exhibit microscopic phase separation, reflecting irreversible adsorption and limited lateral reorganization of the polymer component. With increasing fluid-phase lipid fraction, these hybrid, supported membranes undergo a fluidity transition, producing a fully percolating fluid lipid phase beyond a critical area fraction, which matches the percolation threshold for the immobile point obstacles. This then suggests that polymer-lipid hybrid membranes might be useful models for studying obstructed diffusion, such as occurs in lipid membranes containing proteins.

Dynamics of Membrane Proteins within Synthetic Polymer Membranes with Large Hydrophobic Mismatch

“…33 Therefore, these synthetic BCP membranes mimic natural lipid bilayers with respect to the membrane fluidity and do not have to be blended with fast diffusing lipids in order to increase their fluidity. 34 Furthermore, the functional incorporation of a small biopore (gramicidin) with height in the range of the present MPs in BCP giant unilamellar vesicles (BCP-GUVs), similar to the GUVs used in this study, was reported very recently. 21 Gramicidin was successfully inserted in synthetic membranes up to 13 nm thick, whereas thicker membranes (for example 16.2 nm) prevented a functional biopore insertion.…”

Hybrid Lipid-Polymer Bilayers: pH-Mediated Interactions between Hybrid Vesicles and Glass

“…Generating supported polymer bilayers and supported hybrid lipid/polymer bilayers (SHBs) offers another practical approach towards robust and stable biomimetic platforms. Indeed, there is a growing interest in understanding and exploiting the formation of SHB films in the past few years [22][23][24][25][26][27], including the use of amphiphilic polymers to complement the library of conventional lipids. Such hybrid materials have recently been highlighted as an important development toward biomimetic interfaces [28,29].…”

Large and Giant Unilamellar Vesicle(s) Obtained by Self-Assembly of Poly(dimethylsiloxane)-b-poly(ethylene oxide) Diblock Copolymers, Membrane Properties and Preliminary Investigation of Their Ability to Form Hybrid Polymer/Lipid Vesicles

“…Thus far, relatively little information is available about the structure, chemical nature, and molar mass of copolymers that could mix ideally with phospholipids. Most commonly, poly(butadiene) [3][4][5][6][7][8][9][10][11][12] and poly(dimethylsiloxane) [13][14][15][16][17][18][19][20] have been used as hydrophobic block, while studies with poly(isobutene) [21][22][23], poly(caprolactone) [24,25], poly(isoprene) [26], and poly(laurylacrylate) [27] have also been reported. Poly(ethylene oxide) is by far the most used hydrophilic block, although few studies report the use of hydrophilic thermo-responsive blocks such as poly(2-isopropyl-2-oxazoline) [28] and poly(ethylene glycoldiacrylate) [27].…”