The Key Role of Temperature and Lipid Composition in Modulating the Intake of Gold Nanoparticles into the Plasma Membrane

International audienceMonolayer-protected gold nanoparticles are emerging as promising candidates for drug delivery due to their ability to permeate through plasma membranes. Understanding the molecular mechanisms of such complex systems is crucial to control cell permeation and to develop efficient biomedical delivery applications based on nanoscale gold nanoparticles. Here, neutron reflectometry (NR) and molecular dynamics (MD) simulations were used to shed light on the interaction between cationic gold nanoparticles (AuNPs) and model lipid membranes and the consequences thereof. Atomistic simulations predicted that there is a free energy barrier that has to be overcome to enforce AuNPs to partition into a DSPC bilayer. NR experiments confirmed the prediction, showing that AuNP encapsulation takes place only at temperatures higher than ∼330 K. Meanwhile, in a mixture of DSPC-DSPG (3:1), experiments showed that the adsorption of AuNPs to the membrane is weak; the nanoparticles were readily released during annealing. Coarse-grained MD simulations used to interpret this behaviour indicated that in this mixture DSPGs migrate around AuNPs, thereby weakening their interaction with the surface and leading to detachment of AuNPs at high temperatures. NR experiments also confirmed this by showing that in the presence of negative lipids (DSPG), desorption of AuNPs is associated with a reduced coverage of the floating bilayer, suggesting that some lipids, which comprise both DSPC and DSPG, are extracted and left the bilayer. Finally, the results indicated that the crowding of lipids over the nanoparticles shields the electrostatic interaction between cationic nanoparticles, thus fostering their aggregation on the membrane surface and driving the membrane composition to be locally asymmetric, causing membrane instability