Lipid layers on polyelectrolyte multilayer supports

Abstract

The mechanism of formation of supported lipid layers from phosphatidylcholine and phosphatidylserine vesicles in solution on polyelectrolyte multilayers was studied by a variety of experimental techniques. The interaction of zwitterionic and acidic lipid vesicles, as well as their mixtures, with polyelectrolyte supports was followed in real time by micro-gravimetry. The fabricated lipid-polyelectrolyte composite structures on top of multilayer coated colloidal particles were characterized by flow cytometry and imaging techniques. Lipid diffusion over the macroscopic scale was quantified by fluorescence recovery after photobleaching, and the diffusion was related to layer connectivity. The phospholipid-polyelectrolyte binding mechanism was investigated by infrared spectroscopy. A strong interaction of polyelectrolyte primary amino groups with phosphate and carboxyl groups of the phospholipids, leading to dehydration, was observed. Long-range electrostatic attraction was proven to be essential for vesicle spreading and rupture. Fusion of lipid patches into a homogeneous bilayer required lateral mobility of the lipids on the polyelectrolyte support. The binding of amino groups to the phosphate group of the zwitterionic lipids was too weak to induce vesicle spreading, but sufficient for strong adsorption. Only the mixture of phosphatidylcholine and phosphatidylserine resulted in the spontaneous formation of bilayers on polyelectrolyte multilayers. The adsorption of phospholipids onto multilayers displaying quarternary ammonium polymers produced a novel 3D lipid polyelectrolyte structure on colloidal particles.

Bioreactor droplets from liposome-stabilized all-aqueous emulsions

“…This could offer substantial advantages in bioreactor construction, particularly for biomimetic systems where complex mixtures of macromolecules in nearly identical interior microenvironments are desirable across a population of bioreactors, and where the impermeability of giant vesicle lipid bilayer membranes to even relatively small solutes restricts the types of reactions that can be performed. The observation that aqueous/aqueous interfaces can template assembly of liposome submonolayers also suggests the intriguing possibility that such structures could ultimately be converted into contiguous lipid bilayer membranes by rupture and in-plane restructuring of the assembled liposomes, similar to the formation of supported lipid bilayers on bare and polymercoated solid surfaces [51][52][53] . Such a process would be of interest for generating uniform populations of 'pre-loaded' artificial cells and could serve as a mechanism for cellularization of primitive Pickering-style protocells.…”

Characterization of lipid bilayers adsorbed on spherical LbL-support

“…10,11,14 In this regard, it has already been shown that LbL particles are sufficiently taken up by living cells, which subsequently express proteins that are encoded on the plasmid encapsulated into the LbL particles. 12 Typically, the particle uptake occurs in a non-receptor-mediated endocytotic pathway.…”

“…8 Spherical supported membranes are formed not only on silica beads 9 but also on layer-by-layer (LbL) polymer coated surfaces. [10][11][12] Such LbL particles and capsules are generated by adsorption of anionic and cationic polyelectrolytes on spherical support in an alternating arrangement. 13 LbL particles can be easily functionalized, are highly stable, offer a large size range (from 100 nm to 15 mm), are monodisperse, possess a tuneable permeability, and are biodegradable.…”

“…A recent study on lipid coated LbL particles indicated that the formation of lipid bilayers depends strongly on the surface properties of the support, the biophysical properties of the polyelectrolytes, the ionic strength of the buffer, the roughness of the surface, the hydration state, the operating buffers, and the lipid composition and size of the vesicles used for the deposition of the membranes onto the particles. 10,12 It has been shown that the best bilayer coating was achieved by using LbL particles composed of poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate) (PSS) with PAH as the top layer and 50 nm diameter vesicles consisting of 1 : 1 POPC/POPS lipid mixture. 10 The headgroups of both phosphatidylcholine (zwitterionic) and phosphatidylserine (negatively charged) may interact with the positively charged polymer PAH, which constitutes the outermost polyelectrolyte layer, where long-range electrostatic attraction of POPS to PAH is essential for supported bilayer formation.…”

“…10,12 It has been shown that the best bilayer coating was achieved by using LbL particles composed of poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate) (PSS) with PAH as the top layer and 50 nm diameter vesicles consisting of 1 : 1 POPC/POPS lipid mixture. 10 The headgroups of both phosphatidylcholine (zwitterionic) and phosphatidylserine (negatively charged) may interact with the positively charged polymer PAH, which constitutes the outermost polyelectrolyte layer, where long-range electrostatic attraction of POPS to PAH is essential for supported bilayer formation. The membranes deposited onto the LbL particles, however, do not feature all properties of unperturbed bilayers.…”