C. Schwieger, A. Achilles, S. Scholz, J. Rüger, K. Bacia, K. Saalwächter, J. Kressler, A. Blume.
Binding of amphiphilic and triphilic block
copolymers to lipid model membranes: the role of
Soft Matter 10, 6147 (2014).
A novel class of symmetric amphi- and triphilic (hydrophilic, lipophilic, fluorophilic) block copolymers has
been investigated with respect to their interactions with lipid membranes. The amphiphilic triblock
copolymer has the structure PGMA20-PPO34-PGMA20 (GP) and it becomes triphilic after attaching
perfluoroalkyl moieties (F9) to either end which leads to F9-PGMA20-PPO34-PGMA20-F9 (F-GP). The hydrophobic poly(propylene oxide) (PPO) block is sufficiently long to span a lipid bilayer. The
poly(glycerol monomethacrylate) (PGMA) blocks have a high propensity for hydrogen bonding. The
hydrophobic and lipophobic perfluoroalkyl moieties have the tendency to phase segregate in aqueous as
well as in hydrocarbon environments. We performed differential scanning calorimetry (DSC)
measurements on polymer bound lipid vesicles under systematic variation of the bilayer thickness, the
nature of the lipid headgroup, and the polymer concentration. The vesicles were composed of
phosphatidylcholines (DMPC, DPPC, DAPC, DSPC) or phosphatidylethanolamines (DMPE, DPPE, POPE).
We showed that GP as well as F-GP binding have membrane stabilizing and destabilizing components.
PPO and F9 blocks insert into the hydrophobic part of the membrane concomitantly with PGMA block
adsorption to the lipid headgroup layer. The F9 chains act as additional membrane anchors. The
insertion of the PPO blocks of both GP and F-GP could be proven by 2D-NOESY NMR spectroscopy. By
fluorescence microscopy we show that F-GP binding increases the porosity of POPC giant unilamellar
vesicles (GUVs), allowing the influx of water soluble dyes as well as the translocation of the complete
triphilic polymer and its accumulation at the GUV surface. These results open a new route for the
rational design of membrane systems with specific properties.