Controlling the elasticity of lipid membranes with pluronic block copolymers

Pluronic triblock copolymers consisting of a hydrophobic poly(propylene-oxide) (PPO) block, flanked by two hydrophilic poly(ethylene-oxide) (PEO) blocks have been widely investigated in drug delivery applications as membrane sealants and plasticizers. However, despite a single pluronic (F68) being FDA approved, there is minimal insight into how block copolymer architecture can be engineered to dictate membrane response. Here, we investigate the influence of the structure of the pluronic on the interaction with artificial biological membranes using the large-area model biomembrane (LAMB) technique. We systematically measured the change in membrane tension and elasticity of a planar, freestanding DOPC membrane upon interaction with several pluronics with with varying PEO and PPO chain lengths and HLB values. Based on the membrane tension - area relationship, the apparent elasticity modulus was calculated. Interestingly, the main factor determining the membrane elasticity is the length of the hydrophilic PEO chain, rather than the hydrophobic PPO block. We also discuss the effect of concentration above and below the cmc on the membrane elasticity. These findings may prove beneficial for future medical applications of pluronics as treatment for membrane-tension mediated maladies.