Tailoring a Solvent-Assisted Method for Solid-Supported Hybrid Lipid-Polymer Membranes

Abstract

Combining amphiphilic block copolymers and phospholipids opens new opportunities for the preparation of artificial membranes. The chemical versatility and mechanical robustness of polymers together with the fluidity and biocompatibility of lipids afford hybrid membranes with unique properties that are of great interest in the field of bioengineering. Owing to its straightforwardness, the solvent-assisted method (SA) is particularly attractive for obtaining solid-supported membranes. While the SA method was first developed for lipids and very recently extended to amphiphilic block copolymers, its potential to develop hybrid membranes has not yet been explored. Here, we tailor the SA method to prepare solid-supported polymer-lipid hybrid membranes by combining a small library of amphiphilic diblock copolymers poly(dimethyl siloxane)-poly(2-methyl-2-oxazoline) and poly(butylene oxide)-block-poly(glycidol) with phospholipids commonly found in cell membranes including 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine, sphingomyelin, and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(glutaryl). The optimization of the conditions under which the SA method was applied allowed for the formation of hybrid polymer-lipid solid-supported membranes. The real-time formation and morphology of these hybrid membranes were evaluated using a combination of quartz crystal microbalance and atomic force microscopy. Depending on the type of polymer-lipid combination, significant differences in membrane coverage, formation of domains, and quality of membranes were obtained. The use of the SA method for a rapid and controlled formation of solid-supported hybrid membranes provides the basis for developing customized artificial hybrid membranes.

Figure 1

Schematic representation of a lipid-polymer hybrid membrane assembly formed by the solved-assisted method.

Figure 2

QCM-D plots of hybrid membrane formation: schematic representation of (A) normalized frequency shift and (B) and dissipation of DPPC lipid and PDMS–PMOXA, PBO–PG block copolymers. (C) Comparisons of different DPPC:PDMS₆₁–PMOXA₉ mixtures and DPPC:PBO₅₀–PG₁₈ in 50:50 weight ratio (↓1,4,6 = phosphate buffer saline, PBS, ↓2 = EtOH, ↓3 = polymer–DPPC solution, ↓5 = bovine serum albumin, BSA). The seventh overtone is presented.

Figure 3

Scatter plot of different hybrid membranes composed of lipids and PDMS–PMOXA (A) and PBO–PG (B) copolymers. Contour plot reporting the membrane coverage as a function of the PDMS block length and the lipid number of carbon units (C).

Figure 4

AFM height and comparison of phase images of membranes with good quality in terms of coverage and phase separation measured in air (A) and in liquid (B). Defected membranes were obtained with the SA method in the air (C). The presented AFM micrographs are representative of each case of hybrid membrane for which duplicates were conducted and 5 micrographs for each sample were recorded.