Surface miscibility of EPC/DOTAP/DOPE in binary and ternary mixed monolayers

Area of Science:

• Biophysics
• Materials Science
• Nanotechnology

Background:

• Lipid monolayers are crucial for understanding self-assembled systems.
• Liposomes formulated with EPC/DOPE/DOTAP are effective DNA non-viral vectors.
• Lipid packing and interactions influence liposome stability and function.

Purpose of the Study:

• To characterize the packing and miscibility of pseudo-ternary mixed Langmuir monolayers of EPC, DOTAP, and DOPE.
• To investigate the intermolecular forces and interactions within these lipid mixtures.
• To correlate monolayer behavior with liposome formulation for DNA non-viral vectors.

Main Methods:

• Surface pressure (π)-molecular area (A) isotherms were measured for pseudo-ternary and binary lipid mixtures.
• Miscibility was assessed using the additivity rule and calculating excess free energy of mixture (ΔG(Exc)).
• Surface compressional modulus (C(s)(-1)) was used to deduce lipid interactions.

Main Results:

• The miscibility and packing of EPC/DOPE/DOTAP monolayers depend on lipid composition and polar head groups.
• Attractive forces dominate at lower DOPE concentrations, while repulsive forces emerge in DOPE-rich mixtures due to DOTAP.
• The ternary monolayer exhibits distinct configurations influenced by DOPE content, mirroring DOPE/DOTAP binary mixtures.

Conclusions:

• Lipid interactions and packing in EPC/DOPE/DOTAP monolayers are complex and composition-dependent.
• Understanding these interactions is key to optimizing liposome stability for non-viral gene delivery.
• The study provides insights into the self-assembly behavior relevant for advanced drug delivery systems.