Star Polymers and Their Interaction with Lipid Membranes Via Coarse-Grained Molecular Simulations

Star polymers (SPs) of fifteen different architectures/ compositions were simulated both in solution and interacting with a model lipid membrane using a MARTINI coarse-grained model. These simulations yielded information on the equilibrium structure-property relationships of such macromolecules and the energetics of active membrane transport. Star polymers exist in solution in a nearly spherical shape and their size depends on both the total length of their polymer arms and the degree of hydrophobicity, with variation of ~30% observed in the radius of gyration between a fully hydrophilic SP and a fully hydrophobic SP. These properties were also measured during membrane translocation and SPs presented deformations of up to 40% or 100% depending on the length of the polymers arms. Such large deviations in size and shape could ultimately lead to changes in the drug loading/ release behavior. The deformations of the membrane were also recorded as was the energy barrier to transport which varied up to 100% depending on the hydrophobicity of the SP. The extraction of lipid molecules into the SP post-translocation was also observed, serving as a further proof-of-concept for the potential of these amphiphilic macromolecules to act as nanocarriers.