Interparticle Dispersion, Membrane Curvature, and Penetration Induced by Single-Walled Carbon Nanotubes Wrapped with Lipids and PEGylated Lipids

Single-walled carbon nanotubes (SWNTs) wrapped with different types of lipids and polyethylene glycol (PEG)-grafted lipids were simulated with lipid bilayers. Simulations were carried out with the previously parametrized coarse-grained (CG) SWNT and PEG force fields that had captured the experimentally observed conformations of self-assembled SWNT–lipid complexes and phase behavior of PEG-grafted lipids. Simulations of multiple copies of the SWNT in water show that all pure SWNTs aggregate, lipid-wrapped SWNTs partially aggregate, but those wrapped with lipids grafted to PEG (Mw = 550) completely disperse, indicating the effect of short PEG chains on interparticle aggregation, in agreement with experiment. Starting with initial SWNT orientation parallel to the bilayer surface, SWNTs wrapped with lysophospholipids and PEG (Mw = 550)-grafted lipids insert into the hydrophobic region of the bilayer, while SWNTs wrapped with phospholipids and longer PEG (Mw = 2000)-grafted lipids do not. These indicate that S...