Switchable Lipid Provides pH-Sensitive Properties to Lipid and Hybrid Polymer/Lipid Membranes

Abstract

Blending amphiphilic copolymers and lipids constitutes a novel approach to combine the advantages of polymersomes and liposomes into a new single hybrid membrane. Efforts have been made to design stimuli-responsive vesicles, in which the membrane’s dynamic is modulated by specific triggers. In this investigation, we proposed the design of pH-responsive hybrid vesicles formulated with poly(dimethylsiloxane)-block-poly(ethylene oxide) backbone (PDMS36-b-PEO23) and cationic switchable lipid (CSL). The latter undergoes a pH-triggered conformational change and induces membrane destabilization. Using confocal imaging and DLS measurements, we interrogated the structural changes in CSL-doped lipid and hybrid polymer/lipid unilamellar vesicles at the micro- and nanometric scale, respectively. Both switchable giant unilamellar lipid vesicles (GUV) and hybrid polymer/lipid unilamellar vesicles (GHUV) presented dynamic morphological changes, including protrusions and fission upon acidification. At the submicron scale, scattered intensity decreased for both switchable large unilamellar vesicles (LUV) and hybrid vesicles (LHUV) under acidic pH. Finally, monitoring the fluorescence leakage of encapsulated calcein, we attested that CSL increased the permeability of GUV and GHUV in a pH-specific fashion. Altogether, these results show that switchable lipids provide a pH-sensitive behavior to hybrid polymer/lipid vesicles that could be exploited for the triggered release of drugs, cell biomimicry studies, or as bioinspired micro/nanoreactors.

Polymer–Lipid Hybrid Materials

“…Sebai et al hybridized azobenzene-modified polymers with lipids in the form of GHUVs so that vesicles have light-triggable membrane permeability and controlled release of cargo upon exposure to violet visible light (Figure ). Passos Gibson et al formulated a pH-responsive hybrid vesicles comprising PDMS 36 - b -PEO 23 and cationic switchable lipids with two alkyl chains on a di­(methoxyphenyl)­pyridine pH-switchable unit. Upon acidification, the GHUVs display morphological changes including protrusions and fission due to structural change of the lipid molecules .…”

“…Passos Gibson et al formulated a pH-responsive hybrid vesicles comprising PDMS 36 - b -PEO 23 and cationic switchable lipids with two alkyl chains on a di­(methoxyphenyl)­pyridine pH-switchable unit. Upon acidification, the GHUVs display morphological changes including protrusions and fission due to structural change of the lipid molecules . Moreover, the authors showed that the GHUVs permit pH-controlled calcein release behavior, which may be relevant to the design of systems for triggered drug release, artificial cells, and micro/nanoreactors.…”

Polymer Micelles vs Polymer–Lipid Hybrid Vesicles: A Comparison Using RAW 264.7 Cells

“… 27 , 28 They offer an alternative to polymersomes and liposomes that benefits from modern polymer chemistry and the inherent self-assembly capability of phospholipids, resulting in stable vesicles with sufficient permeability to be used for encapsulated catalysis. Amphiphilic block copolymers that are used in this context include poly(dimethylsilane)- block -poly(ethylene oxide) 29 − 31 and poly(butadiene)- block -poly(ethylene oxide). 32 , 33 We have focused our efforts on block copolymer with a poly(cholesteryl methacrylate) as the hydrophobic part while varying the types of hydrophilic extensions.…”

“…Lipid–polymer hybrid vesicles (HVs) are assemblies that have a membrane consisting of both lipids and amphiphilic block copolymers as outlined in earlier reviews , or in sections of more recent reviews. , They offer an alternative to polymersomes and liposomes that benefits from modern polymer chemistry and the inherent self-assembly capability of phospholipids, resulting in stable vesicles with sufficient permeability to be used for encapsulated catalysis. Amphiphilic block copolymers that are used in this context include poly­(dimethylsilane)- block -poly­(ethylene oxide) − and poly­(butadiene)- block -poly­(ethylene oxide). , We have focused our efforts on block copolymer with a poly­(cholesteryl methacrylate) as the hydrophobic part while varying the types of hydrophilic extensions. For instance, HVs prepared from 1,2-dioleoyl- sn -glycero-3-phosphocholine (DOPC) and an amphiphilic block copolymer with poly­(2-(dimethylamino)­ethyl methacrylate) as the hydrophilic block were able to induce lysosomal escape via the proton sponge effect .…”

Composite Aramid Membranes with High Strength and pH-Response

“…As one of the environmental responsiveness of “smart” membranes, pH-responsive membranes can adjust their flux and separation performance with the change of environmental pH value [ 1 , 2 , 3 ]. These characteristics allow the pH-responsive membranes to be used in many fields, especially water and wastewater treatment and desalination, drug release biotechnology and food industry [ 4 , 5 , 6 ].…”