Probing the structure of PEGylated-lipid assemblies by coarse-grained molecular dynamics

Wataru Shinoda, Dennis E. Discher, Michael L. Klein, Sharon M. Loverde

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

Poly(ethylene glycol) (PEG) and various zwitterionic species are now used routinely as components in soft biomaterials. The study of mixtures composed of PEGylated-lipids with zwitterionic lipids provides an excellent opportunity to understand molecular interactions in such systems. To this end, we examine the liposome/bicelle/micelle phase behavior of such mixtures in bulk solution and as monolayers at the air-water interface, utilizing a coarse-grained molecular-dynamics (CG-MD) approach rooted in experimental parameters that inform the nature of the short-range interactions. Specifically, we examine mixtures of PEGylated lipid and dimyristoylphosphatidylcholine (DMPC) lipid monolayers and find the standard force fields yield calculated surface tensions in agreement with experiment. Long-time CG-MD simulations (∼0.5 microsecond) of the self-assembly for different concentrations of PEG indicate the critical micellar size for the aggregate to form a bicelle from a spherical micellar nucleus. At lower PEG concentrations we find self-assembly of the PEGylated lipid into a liposome coexisting with a mixture of smaller bicelles. Examination of large individual bicelles (1000 lipids) at increasing concentrations of PEG indicates that the degree of PEG de-mixing towards the outer radius of the bicelle is correlated with the overall concentration of PEG in the bicelle. The CG-MD approach used herein should be a useful complement to experimental studies designed to probe solute (drug) interactions with such membrane systems.

Original languageEnglish
Pages (from-to)11549-11556
Number of pages8
JournalSoft Matter
Volume9
Issue number48
DOIs
Publication statusPublished - Dec 28 2013
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics

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