Efficient liposome fusion to phase-separated giant vesicles

Area of Science:

• Biochemistry
• Biophysics
• Materials Science

Background:

• Lateral phase heterogeneity in biomembranes influences cellular functions and molecular interactions.
• Membrane fusion is a critical process affected by membrane composition and physical state.

Purpose of the Study:

• Investigate how membrane phase state (fluid/gel), phase coexistence, and fusion-mediated lipid incorporation affect membrane fusion.
• Determine if fusion can be targeted to specific domains on phase-separated membranes.
• Understand the impact of fusion on membrane organization and phase separation.

Main Methods:

• Utilized cationic fluid large unilamellar vesicles (LUVs) and neutral/anionic giant unilamellar vesicles (GUVs) with varying lipid compositions.
• Quantified fusion efficiency using fluorescence microscopy-based lipid and content mixing assays.
• Assessed fusion dynamics with flow chamber devices and bilayer thermal behavior with differential scanning calorimetry (DSC).

Main Results:

• Extensive fusion occurred in single-component GUVs only with fluid, negatively charged acceptor membranes.
• Phase-separated GUVs showed high fusion efficiency, even with anionic gel phases, with phase separation slightly increasing fusion.
• Extensive fusion led to gel domain dissolution due to the incorporation of fluid-state lipids from fusogenic liposomes.

Conclusions:

• Membrane phase state, charge, and phase separation play crucial roles in regulating membrane fusion.
• Fusion significantly alters membrane organization by incorporating exogenous lipids and dissolving gel domains.
• Findings offer insights into cell-liposome interactions relevant for drug delivery systems.