Perfluorinated Moieties Increase the Interaction of Amphiphilic Block Copolymers with Lipid Monolayers

Abstract

The interaction of amphiphilic and triphilic block copolymers with lipid monolayers has been studied. Amphiphilic triblock copolymer PGMA20-PPO34-PGMA20 (GP) is composed of a hydrophobic poly(propylene oxide) (PPO) middle block that is flanked by two hydrophilic poly(glycerol monomethacrylate) (PGMA) side blocks. The attachment of a perfluoro-n-nonyl residue (F9) to either end of GP yields a triphilic polymer with the sequence F9-PGMA20-PPO34-PGMA20-F9 (F-GP). The F9 chains are fluorophilic, i.e., they have a tendency to demix in hydrophilic as well as in lipophilic environments. We investigated (i) the adsorption of both polymers to differently composed lipid monolayers and (ii) the compression behavior of mixed polymer/lipid monolayers. The lipid monolayers are composed of phospholipids with PC or PE headgroups and acyl chains of different length and saturation. Both polymers interact with lipid monolayers by inserting their hydrophobic moieties (PPO, F9). The interaction is markedly enhanced in the presence of F9 chains, which act as membrane anchors. GP inserts into lipid monolayers up to a surface pressure of 30 mN/m, whereas F-GP inserts into monolayers at up to 45 mN/m, suggesting that F-GP also inserts into lipid bilayer membranes. The adsorption of both polymers to lipid monolayers with short acyl chains is favored. Upon compression, a two-step squeeze-out of F-GP occurs, with PPO blocks being released into the aqueous subphase at 28 mN/m and the F9 chains being squeezed out at 48 mN/m. GP is squeezed out in one step at 28 mN/m because of the lack of F9 anchor groups. The liquid expanded (LE) to liquid condensed (LC) phase transition of DPPC and DMPE is maintained in the presence of the polymers, indicating that the polymers can be accommodated in LE- and LC-phase monolayers. These results show how fluorinated moieties can be included in the rational design of membrane-binding polymers.

Polyphilicity—An Extension of the Concept of Amphiphilicity in Polymers

“…Furthermore, when a hydrophilic–lipophilic polymer is supplied with a third structural element, it expands the possibilities for the development of self-assembled multi-compartment macromolecules [92,93,94,95,96,97,98,99,100,101,102,103,104]. It often has remarkable effects on the catalytic behavior [92,105,106], the interaction with biological membranes [107,108,109,110], or the transport of active substances [103,109,111,112].…”

“…Monolayer investigations of the shorter polymer with (PGMA 24 ) at the air–water interface and analysis of the interaction of lipid monolayers with the triphilic and amphiphilic (without fluorinated part) block copolymers were performed. It is concluded that the fluorinated segments located at the polymer end in the triphilic polymer significantly inhibit its removal from the lipid layer, compared to amphiphilic molecules [108].…”

Rational design of block copolymer self-assemblies in photodynamic therapy

“…The polybetaine generating the smaller expansion of the monolayer was also the one showing the least cytotoxicity on human breast carcinoma cell MCF7. Schwieger et al [163] used monolayers made of different types of lipids, changing the nature of the polar heads or of the chains, to investigate the interactions between the lipids and two types of PGMA-PPO-PGMA triblock copolymers, one presenting fluorinated end chains. They showed that the fluorinated polymer incorporated more strongly in the monolayer than the non-fluorinated one.…”

Effect of Perfluoroalkyl Endgroups on the Interactions of Tri-Block Copolymers with Monofluorinated F-DPPC Monolayers

“…The replacement of poly(ethylene oxide) block in these polymers by poly(glycerol monomethyl methacrylate) gives rise to a new type of polymers, which have greater ability to interact with membranes compared to poloxamers [18,26,27,28,29]. The polymer retention in membranes is further enhanced upon end capping of the amphiphilic triblock copolymers with perfluorinated moieties [30,31,32]. The resulting macromolecules are polyphilic, simply because their perfluorinated segments are hydrophobic as well as lipophobic [33].…”

“…In order to understand the significance of polymers bearing such components, it is vital to study the interactions of these polymers with biological membranes or their simplified mimics [18]. The interactions between block copolymers and membrane lipids, including DPPC are affected upon α,ω perfluoroalkylation of block copolymers [31,32]. There is a solitary study available in literature on the effect of human serum albumin on F-DPPC monolayers [47], however the effect of polymers on monolayers or bilayers of F-DPPC has never been reported.…”