Magneto‐Thermal Release from Nanoscale Unilamellar Hybrid Vesicles

Abstract

Hybrid vesicles of lipid and amphiphilic block copolymer combine the biological and functional versatility of lipid delivery systems with the mechanical stability and robustness of polymersomes. While studies of hybrid systems for ease of characterization have focused on giant vesicles, most encapsulation and release applications require nanoscale (large) unilamellar vesicles. We investigate the structure and physical characteristics important for thermal actuation of vesicle‐forming blends of saturated phospholipid, polybutadiene‐b‐poly(ethylene oxide) and thermoresponsive polyisoprene‐b‐poly(N‐isopropylacryl amide) that are additionally loaded with hydrophobic superparamagnetic nanoparticles in the vesicle membrane and resized to large unilamellar vesicles. Lipid/diblock copolymer hybrid vesicles are shown to be the most efficient option to trigger release of encapsulated compounds by application of an external magnetic field causing local hyperthermia. This superiority is shown to depend on the controlled formation of nanoscale lipid domains in the hybrid vesicle membrane and the efficient loading of hydrophobic nanoparticles into the diblock copolymer membrane that retains its stability.

Thermoresponsive Polypeptoid‐Coated Superparamagnetic Iron Oxide Nanoparticles by Surface‐Initiated Polymerization

“…A dense, stably anchored polypeptoid shell should allow for colloidal stability of the SPION by steric repulsion, which was shown to be beneficial for SPION used as magnetic resonance contrast agent, potential drug delivery vehicle or magnetically actuated release vehicles . The initial ligand replacement of oleic acid with nitrodopamine yields SPION with high initiator density that should convert into a high grafting density of the brush …”

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].…”

The combination of block copolymers and phospholipids to form giant hybrid unilamellar vesicles (GHUVs) does not systematically lead to “intermediate” membrane properties

“…These emerging systems have already been the subject of two reviews. 2,3 A significant number of studies have focused on their use in different fields, such as drug delivery [4][5][6][7] , drug targeting, 8 nanoreactors, 7,9,10 biomolecular recognition and interaction with nanoparticles [11][12][13][14] , or their interaction with biological media. 15 So far, only a relatively moderate part of the work published on the subject has focused on the selfassembly problematic: how can we modulate the phase separation process during the self-assembly, preventing formation of separated liposomes and polymersomes, and obtain membranes with lipid domains of controlled size?…”