title: Exchange kinetics of protein-functionalized micelles and liposomes studied by Förster resonance energy transfer.
abstract: Protein-functionalized micelles and liposomes are attractive delivery systems for applications ranging from targeted drug delivery to molecular imaging. In particular, systems that use pegylated phospholipids have become popular, but little is known about the stability of these lipid-functionalized proteins toward exchange. In this study, Förster resonance energy transfer (FRET) between the fluorescent proteins ECFP and EYFP was used to investigate the lipid exchange behavior of protein-functionalized liposomes and micelles. Native chemical ligation was used as an efficient method to site-specifically couple varying amounts of proteins to pegylated phospholipids. No exchange was observed between protein-functionalized phospholipids in sterically stabilized liposomes. In micelles, however, protein-functionalized lipids were found to exchange with a half-time of exchange ranging from almost 2 h at room temperature to 4 min at 37 degrees C. These pegylated micelles remained intact at lipid concentrations down to 0.15 microM, indicating that they are even more stable than previously assumed. The results obtained in this study provide a useful frame of reference for assessing the potential role of protein exchange in biomedical applications of these lipid-based nanoparticles.
authors.affiliation: Laboratory of Chemical Biology, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Sanne W A
authors.initials: SW
authors.lastname: Reulen
authors.forename: Maarten
authors.initials: M
authors.lastname: Merkx
mesh_terms: D031541:Fluorescence Resonance Energy Transfer; D049452:Green Fluorescent Proteins / Q000737:chemistry*; D007700:Kinetics; D008081:Liposomes / Q000737:chemistry*; D008823:Micelles
chemical_list: D008081:Liposomes; D008823:Micelles; C527701:enhanced cyan fluorescent protein; D049452:Green Fluorescent Proteins