Physical stability of different liposome compositions obtained by extrusion method

Area of Science:

• Lipid-based drug delivery systems
• Physical chemistry of lipid formulations

Background:

• Liposomes are versatile drug delivery vehicles.
• Understanding liposome physical stability is crucial for formulation development.

Purpose of the Study:

• To evaluate the physical stability of six different liposome compositions.
• To determine the impact of formulation components on liposome stability under various temperature conditions.

Main Methods:

• Liposomes were prepared using the extrusion method through 0.1-micron polycarbonate membranes.
• Physical stability was assessed at -20°C, room temperature, 4°C, and 50°C over 40 days.
• Vesicle size, polydispersity, captured volume, and lamellarity were analyzed using photon correlation spectroscopy.

Main Results:

• Liposome compositions containing cholesterol (CHOL) showed enhanced stability at 4°C.
• Liposomes with sphingomyelin (SFM) or stearylamine (STE) exhibited high physical stability.
• Dipalmitoylphosphatidylcholine (DPPC) liposomes were stable at room temperature.
• Stearylamine (STE) maintained bilayer integrity below 0°C without cryoprotectants.
• All tested compositions were metastable at 50°C.
• Extruded vesicles exhibited non-sphericity, leading to lower-than-predicted captured volumes.
• Stearylamine (STE) and dicetyl phosphate (DCP) formulations resulted in vesicles with increased lamellarity.

Conclusions:

• Liposome formulation significantly impacts physical stability.
• Cholesterol, sphingomyelin, and stearylamine are key components for enhancing liposome stability.
• Specific formulations offer stability advantages at different temperature ranges, crucial for storage and application.