Phase structure of liposome in lipid mixtures

► The relationship between the lipid mixture phase structure and the stability of gas microbubble ultrasound imaging systems was investigated. ► The phase behavior of a ternary lipid mixture in water with cosolvents was used. ► The polar PEG side chains from DPPE-PEG had a significant impact on the...

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Bibliographic Details
Published in:Chemistry and physics of lipids 2011-11, Vol.164 (8), p.722-726
Main Authors: Zhang, Tianxi, Li, Yuzhuo, Mueller, Anja
Format: Article
Language:English
Subjects:
Aggregation
Contrast Media - chemistry
fluorescence
image analysis
light scattering
Lipids
Lipids - chemistry
Liposome
Liposomes - chemistry
micelles
Microbubbles
nuclear magnetic resonance spectroscopy
Phase structure
Phase Transition
Polyethylene Glycols - chemistry
ultrasonography
Ultrasonography - methods
Ultrasound image
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Summary:► The relationship between the lipid mixture phase structure and the stability of gas microbubble ultrasound imaging systems was investigated. ► The phase behavior of a ternary lipid mixture in water with cosolvents was used. ► The polar PEG side chains from DPPE-PEG had a significant impact on the phase microstructure. ► The microbubbles of an ultrasound imaging system are stabilized by lipid bilayers, not micelles. Gas microbubbles present in ultrasound imaging contrast agents are stabilized by lipid aggregates that typically contain a mixture of lipids. In this study, the phase structure of the lipid mixtures that contained two or three lipids was investigated using three different methods: dynamic light scattering, 1H NMR, and microfluidity measurements with fluorescence probes. Three lipids that are commonly present in imaging agents (DPPC, DPPE-PEG, and DPPA) were used. Two types of systems, two-lipid model systems and simulated imaging systems were investigated. The results show that liposomes were the dominant aggregates in all the samples studied. The polar PEG side chains from the PEGylated lipid lead to the formation of micelles and micellar aggregates in small sizes. In the ternary lipid systems, almost all the lipids were present in bilayers with micelles absent and free lipids at very low concentration. These results suggest that liposomes, not micelles, contribute to the stabilization of microbubbles in an ultrasound imaging contrast agent.
ISSN:0009-3084
1873-2941
DOI:10.1016/j.chemphyslip.2011.08.004