Minimum free energy paths for a nanoparticle crossing the lipid membrane

Abstract

Within self-consistent field theory, we develop an “on-the-fly” string method to compute the minimum free energy path for several activated processes involving a charged, solvophobic nanoparticle and a lipid membrane. Under tensions well below the mechanical stability limit of the membrane, and in the regime where the event can occur on experimentally relevant time scales, our study suggests that there can be at least three competing pathways for crossing the membrane: (1) particle-assisted membrane rupture, (2) particle insertion into a metastable pore followed by translocation and membrane resealing, and (3) particle insertion into a metastable pore followed by membrane rupture. In the context of polymer-based gene delivery systems, we discuss the implications of these results for the endosomal escape mechanism.