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Surface phase behavior and microstructure of lipid/PEG-emulsifier monolayer-coated microbubbles
Mark A Borden1, Gang Pu, Gabriel J Runner
1Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA.
Colloids and Surfaces. B, Biointerfaces
|July 21, 2004
Summary
Researchers studied microbubble shells using Langmuir troughs and fluorescence microscopy. They found that lipid and emulsifier mixtures form complex microstructures, influencing microbubble design for biomedical applications.
Area of Science:
- Materials Science
- Biomedical Engineering
- Surface Chemistry
Background:
- Microbubbles are crucial for biomedical applications.
- Understanding the phase behavior of monolayer shells is key to optimizing microbubble performance.
- Phospholipids and polyethylene glycol (PEG)-emulsifiers are common components of microbubble shells.
Purpose of the Study:
- To investigate the phase behavior and microstructure of monolayer shells coating microbubbles.
- To explore the relationship between lipid composition, emulsifier miscibility, and resulting domain morphology.
- To understand the impact of surface pressure and thermal cycling on shell structure and stability.
Main Methods:
- Combined Langmuir trough techniques with fluorescence microscopy.
- Analyzed homologous series of saturated acyl chain phospholipids and PEG-emulsifiers.
- Studied phase separation, domain formation, and squeeze-out phenomena under varying conditions.
Main Results:
- Observed phase coexistence with condensed lipid domains in an emulsifier-rich expanded phase.
- Identified diverse domain morphologies, including networks, influenced by cooling rate and lipid acyl chain length.
- Determined emulsifier squeeze-out near 35 mN/m, leading to lipid-only shells upon further compression.
Conclusions:
- Microbubble shell microstructure is tunable by lipid-emulsifier composition and processing conditions.
- Phase behavior significantly impacts shell integrity and potential applications.
- Findings provide insights for the rational design of advanced microbubbles in medicine.