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Fluorescent Lipids: Functional Parts of Fusogenic Liposomes and Tools for Cell Membrane Labeling and Visualization
Institute of Complex Systems, ICS-7: Biomechanics, Forschungszentrum Jülich GmbH, Jülich 52425, Germany
* Author to whom correspondence should be addressed.
Received: 30 November 2011; in revised form: 10 January 2012 / Accepted: 16 January 2012 / Published: 20 January 2012
Abstract: In this paper a rapid and highly efficient method for controlled incorporation of fluorescent lipids into living mammalian cells is introduced. Here, the fluorescent molecules have two consecutive functions: First, they trigger rapid membrane fusion between cellular plasma membranes and the lipid bilayers of their carrier particles, so called fusogenic liposomes, and second, after insertion into cellular membranes these molecules enable fluorescence imaging of cell membranes and membrane traffic processes. We tested the fluorescent derivatives of the following essential membrane lipids for membrane fusion: Ceramide, sphingomyelin, phosphocholine, phosphatidylinositol-bisphosphate, ganglioside, cholesterol, and cholesteryl ester. Our results show that all probed lipids could more efficiently be incorporated into the plasma membrane of living cells than by using other methods. Moreover, labeling occurred in a gentle manner under classical cell culture conditions reducing cellular stress responses. Staining procedures were monitored by fluorescence microscopy and it was observed that sphingolipids and cholesterol containing free hydroxyl groups exhibit a decreased distribution velocity as well as a longer persistence in the plasma membrane compared to lipids without hydroxyl groups like phospholipids or other artificial lipid analogs. After membrane staining, the fluorescent molecules were sorted into membranes of cell organelles according to their chemical properties and biological functions without any influence of the delivery system.
Keywords: fusogenic liposomes; cellular membrane staining; fluorescent lipids; DiR; Bodipy FL-sphingomyelin; fluorescence microscopy
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Kleusch, C.; Hersch, N.; Hoffmann, B.; Merkel, R.; Csiszár, A. Fluorescent Lipids: Functional Parts of Fusogenic Liposomes and Tools for Cell Membrane Labeling and Visualization. Molecules 2012, 17, 1055-1073.
Kleusch C, Hersch N, Hoffmann B, Merkel R, Csiszár A. Fluorescent Lipids: Functional Parts of Fusogenic Liposomes and Tools for Cell Membrane Labeling and Visualization. Molecules. 2012; 17(1):1055-1073.
Kleusch, Christian; Hersch, Nils; Hoffmann, Bernd; Merkel, Rudolf; Csiszár, Agnes. 2012. "Fluorescent Lipids: Functional Parts of Fusogenic Liposomes and Tools for Cell Membrane Labeling and Visualization." Molecules 17, no. 1: 1055-1073.