Development of molecular models of interfaces using a multi-scale hybrid particle-field approach: application to composite materials and biomembranes

Abstract

The rule of the interface in systems including polymer composites and block-­‐ copolymer interacting with biomembrane has been investigated by computational approach. In particular, for the polymer composite investigation, a system composed of PMMA embedding a silica nanoparticle of 3 nm (diameter), and an analogue system made of MMA and silica nanoparticle have been simulated. The structuration of both, PMMA and MMA close to the surface of the nanoparticle have been evaluated and calculated. As main results we found a stronger structuration of PMMA close to the nanoparticle respect to the MMA bulk. Pluronics based formulations are among the most successful nanomedicines and block-­‐copolymer micelles including drugs are undergoing phase I/II studies as anticancer agents. Using coarse-­‐grained models, molecular dynamics simulations of large-­‐scale systems, modeling Pluronic micelles interacting with DPPC lipid bilayers, on the μs timescale have been performed. Simulations show, in agreement with experiments, a release of Pluronic chains from the micelle to the bilayer. This release changes the size of the micelle, moreover the presence of drug molecules inside the core of the micelle has a strong influence on this process. The picture emerging from the simulations is that the micelle stability is a result of an interplay between drug/micelle core and block-­‐copolymer/bilayer interactions. The equilibrium size of the drug vector shows a strong dependency on the hydrophobicity of the drug molecules embedded into the core of the micelle. In particular, the radius of the micelle shows an abrupt increase in a very narrow range of drug molecule hydrophobicity. [edited by author]