Lipid Membrane Interactions with Polymer-Grafted Nanoparticles

Many recent studies have been performed to investigate the interaction between nanoparticles with lipid membranes. In most of these studies, the nanoparticles interact directly with the membranes through their surfaces. The fluidity and elasticity of a lipid membrane allow it to deform, such as it conforms to the surface of an adhering nanoparticle to an extent determined by the competition between the adhesive interaction and the membrane's curvature energy. An interesting result of these deformations is that they can be long-ranged and, thereby, lead to membrane-curvature-mediated interaction between adhering nanoparticles. This can result in the aggregation of the nanoparticles on the membrane. Furthermore, high adhesive interaction leads to the endocytosis of the nanoparticles. In some applications, both endocytosis and membrane-induced aggregation of nanoparticles are not desirable. Here, we will show that surface modification of the nanoparticles by partially grafting their surfaces with hydrophilic polymers prevents both their endocytosis and aggregation. Systematic simulations, using a coarse-grained implicit-solvent model, with varying values of the grafting density, length of the polymer chains, and strength of the adhesive interaction, are performed to determine the optimal set of parameters to suppress endocytosis and aggregation of polymer-grafted spherical nanoparticles on lipid vesicles.