PEO-b-PPO star-shaped polymers enhance the structural stability of electrostatically coupled liposome/polyelectrolyte complexes.

Camille E Pinguet,Alexander A Steinschulte,Walter Richtering,Jón M Hoffmann,Felix A Plamper,Alexander Yaroslavov,Andrey Sybachin,Dominik Wöll,Esther Ryll,Monia Brugnoni

doi:10.1371/journal.pone.0210898

Camille E Pinguet, Alexander A Steinschulte + Show 8 more

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https://doi.org/10.1371/journal.pone.0210898

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Abstract

We propose a strategy to counteract the salt-driven disassembly of multiliposomal complexes made by electrostatic co-assembly of anionic small unilamellar liposomes and cationic star-shaped polyelectrolytes (made of quaternized poly(dimethylaminoethyl methacrylate) (qPDMAEMA100)3.1). The combined action of (qPDMAEMA100)3.1 and a nonionic star-shaped polymer (PEO12-b-PPO45)4, which comprises diblock copolymer arms uniting a poly(ethylene oxide) PEO inner block and a poly(propylene oxide) PPO terminal block, leads to a stabilization of these complexes against disintegration in saline solutions. Hereby, the anchoring of the PPO terminal blocks to the lipid bilayer and the bridging between several liposomes are at the origin of the promoted structural stability. Two-focus fluorescence correlation spectroscopy verifies the formation of multiliposomal complexes with (PEO12-b-PPO45)4. The polyelectrolyte and the amphiphilic polymer work synergistically, as the joint action still assures some membrane integrity, which is not seen for the mere (PEO12-b-PPO45)4—liposome interaction alone.

Highlights

Small unilamellar liposomes are used in many disciplines for various applications: cosmetics [1], food industry [2], pharmaceutics [3]
Different aspects are examined: 1. The size evolution of multiliposomal complexes, which are formed by addition of (PPO45-PEO12)4 and incorporation of PPO residues into different liposome membranes
The hydrophobic stickers at the end of the arms of the amphiphilic polymer interact with the inner membrane of several liposomes, while the oppositely charged polyelectrolyte leads to an additional electrostatic “gluing” of lipid head groups of various liposomes

Summary

Introduction

Small unilamellar liposomes (spherical bilayer lipids vesicles) are used in many disciplines for various applications: cosmetics [1], food industry [2], pharmaceutics [3]. Liposomes have the advantage to encapsulate hydrophobic substances in the lipidic membrane and hydrophilic substances in the cavity [5, 6]. Stimuli like temperature or pH variation can cause a triggered release [7, 8]. To increase their specific performance, liposomes can be modified. Coatings can increase the stability of the encapsulated compound [9] and maintain its activity [10, 11]. Addition of poly(ethylene oxide) PEO chains as a liposome coating improves the circulation time [12]. Increasing the chain length of PEO enhances the permeability of the membrane and, causes leakage due to the phase

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