Membrane-Specific Binding of 4 nm Lipid Nanoparticles Mediated by an Entropy-Driven Interaction Mechanism

Lipid nanoparticles (LNPs) are a leading biomimetic drug delivery platform due to their distinctive advantages and highly tunable formulations. A mechanistic understanding of the interaction between LNPs and cell membranes is essential for developing the cell-targeted carriers for precision medicine. Here the interactions between sub 10 nm cationic LNPs (cLNPs; e.g., 4 nm in size) and varying model cell membranes are systematically investigated using molecular dynamics simulations. We find that the membrane-binding behavior of cLNPs is governed by a two-step mechanism that is initiated by direct contact followed by a more crucial lipid exchange (dissociation of cLNP's coating lipids and subsequent flip and intercalation into the membrane). Importantly, our simulations demonstrate that the membrane binding of cLNPs is an entropy-driven process, which thus enables cLNPs to differentiate between membranes having different lipid compositions (e.g., the outer and inner membranes of bacteria vs the red blood cell membranes). Accordingly, the possible strategies to drive the membrane-targeting behaviors of cLNPs, which mainly depend on the entropy change in the complicated entropy-enthalpy competition of the cLNP-membrane interaction process, are investigated. Our work unveils the molecular mechanism underlying the membrane selectivity of cLNPs and provides useful hints to develop cLNPs as membrane-targeting agents for precision medicine.