Nanoparticle's Size Effect on Its Translocation Across a Lipid Bilayer: A Molecular Dynamics Simulation

Understanding the interaction between nanoparticles (NPs) and cell membranes (dipalmitoylphosphatidylcholine or DPPC bilayers) is important for the design of drug delivery systems and provides insights into nanotoxicity. Here we have performed coarse-grained molecular dynamics simulations aimed at nanoparticle's size effect on its translocation across a lipid bilayer. Three hydrophobic nanoparticles of different sizes ranging from 1.284 nm to 2.912 nm are modeled in the simulations. The interaction of NPs induces the structural variations of membranes; the larger the NPs are, the more space they need to cross the bilayer, and the more significant changes the bilayer shows. Some thermodynamics quantities such as free energy have been obtained, indicating that the free energy deceases with the increasing size of NPs. However, no obvious energy barrier can be seen in the free energy profiles during the process of NPs' transport. The translocation time of NPs to different positions of the bilayer has also been calculated based on the free energy. The results show that the size of NPs affects the translocation time differently. Our simulation results suggest that the size of NP has significant impacts on its translocation across the lipid bilayer.