Dynamic interaction between oppositely charged vesicles: aggregation, lipid mixing, and disaggregation.

Area of Science:

• Biochemistry
• Materials Science
• Physical Chemistry

Background:

• Small unilamellar vesicles (SUVs) are crucial in drug delivery and biomimetic studies.
• Understanding vesicle interactions is key to controlling their behavior and function.
• Charged lipids influence vesicle aggregation and membrane fusion dynamics.

Purpose of the Study:

• To investigate the dynamic interactions between oppositely charged SUVs.
• To elucidate the mechanisms of aggregation, lipid mixing, and content exchange.
• To compare the effects of different cationic lipids on vesicle interactions.

Main Methods:

• Optical density measurements for aggregation kinetics.
• Fluorescence resonance energy transfer (FRET) for lipid bilayer mixing.
• Fluorescence quenching assays for content leakage.
• Light-scattering analyses and freeze-fracture transmission electron microscopy (FFTEM) for structural changes.

Main Results:

• Immediate aggregation of oppositely charged vesicles.
• Observed lipid bilayer mixing but no evidence of content mixing.
• Spontaneous disaggregation of vesicle aggregates within minutes.
• Neutralization of surface potential upon disaggregation.
• Differential disaggregation speeds based on cationic lipid type.

Conclusions:

• External lipid monolayer exchange occurs between vesicles during interaction.
• Vesicle internal monolayers remain intact, preventing content release.
• The study provides insights into the mechanisms governing charged vesicle interactions and stability.