title: Simulated Permeation and Characterization of PEGylated Gold Nanoparticles in a Lipid Bilayer System.
abstract: PEGylated gold nanoparticles are considered suitable nanocarriers for use in biomedical applications and targeted drug delivery systems. In our previous investigation with the alkanethiol-functionalized gold nanoparticle, we found that permeation across a protein-free phospholipid membrane resulted in damaging effects of lipid displacement and water and ion leakage. In the present study, we carry out a series of coarse-grained molecular simulations to explore permeation of lipid bilayer systems by a PEGylated gold nanoparticle, especially at the bulk-liquid-lipid interface as well as the interface between the two lipid leaflets. Initially, we examine molecular-level details of a PEGylated gold nanoparticle (constructed from cycled annealing) in water and find a distribution of ligand configurations (from mushroom to brush states) present in nanoparticles with medium to high surface coverage. We also find that the characteristic properties of the PEGylated gold nanoparticle do not change when it is placed in a salt solution. In our permeation studies, we investigate events of water and ion penetration as well as lipid translocation while varying the ligand length, nanoparticle surface coverage, and ion concentration gradient of our system. Results from our studies show the following: (1) The number of water molecules in the interior of the membrane during ligand-coated nanoparticle permeation increases with PEGn-SH surface coverage, ligand length, and permeation velocity but is not sensitive to the ion concentration gradient. (2) Lipid molecules do not leave the membrane; instead they complete trans-bilayer lipid flip-flop with longer ligands and higher surface coverages. (3) The lack of formation of stable water pores prevents ion translocation. (4) The PEGylated nanoparticle causes less damage to the membrane overall due to favorable interactions with the lipid headgroups which may explain why experimentalists observe endocytosis of PEGylated nanocarriers in vivo.
authors.affiliation: Department of Chemical Engineering, University of Illinois at Chicago , 810 South Clinton Street, Chicago, Illinois 60607, United States.
authors.forename: Priyanka A
authors.initials: PA
authors.lastname: Oroskar
authors.affiliation: Department of Chemical Engineering, University of Illinois at Chicago , 810 South Clinton Street, Chicago, Illinois 60607, United States.|Department of Chemistry, University of Illinois at Chicago , 845 West Taylor Street, Chicago, Illinois 60607, United States.
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Jameson
authors.affiliation: Department of Chemical Engineering, University of Illinois at Chicago , 810 South Clinton Street, Chicago, Illinois 60607, United States.|Department of Chemical and Biological Engineering, Illinois Institute of Technology , 3300 South Federal Street, Chicago, Illinois 60616, United States.
authors.forename: Sohail
authors.initials: S
authors.lastname: Murad