Interaction and complexation of phospholipid vesicles and triblock copolymers

Mixtures of Pluronic (F-127 or L-61) and phospholipid were investigated for a wide range of Pluronic concentrations (0-15 wt %) using dynamic light scattering, differential scanning calorimetry, and fluorescence microscopy. The present study is aimed at better understanding how the amphiphilic triblock copolymers affect the lipid vesicles, particularly in the high-concentration regime. Our results show that L-61 interacts more strongly with phospholipid vesicles than F-127 when the copolymer is at the unimer state in the solution. For high concentrations, F-127 forms mixed micelles with solubilized lipid molecules in the form of bilayer patches. This novel behavior was observed for the first time. In contrast, more hydrophobic L-61 tends to precipitate with the solubilized lipids as large crew-cut mixed aggregates.