Emulsions stabilized by phospholipids.

Area of Science:

• Colloid and Surface Science
• Materials Science
• Biophysics

Background:

• Phospholipids stabilize parenteral emulsions by adsorbing at oil/water interfaces.
• Molecular structure and interactions influence phospholipid preferred curvature, impacting lamellar phase formation and formulation constraints.

Purpose of the Study:

• Investigate mechanisms governing emulsion stability.
• Provide tools to optimize parenteral emulsion formulations by understanding phospholipid behavior.

Main Methods:

• Phase diagrams of water/phospholipid/oil systems (DOPC/POPC, hexadecane/miglyol 812) were determined.
• Small-angle neutron scattering probed droplet interfaces; Raman spectroscopy quantified adsorbed lipid.
• Metastability of nano and macro emulsions was assessed using light scattering over weeks.

Main Results:

• Nanoemulsions stabilized by lipid monolayers with sufficient positive preferred curvature showed excellent metastability.
• Macroemulsions stabilized by multilayers require positive preferred curvature and adequate interfacial anchorage, which is compromised by increasing preferred curvature.
• Formulation impacts on emulsion metastability were rationalized through preferred curvature, layering, and anchorage analysis.

Conclusions:

• Lipid monolayer stabilization with adequate positive preferred curvature is key for nanoemulsion metastability.
• Macroemulsion stability depends on a balance between preferred curvature and interfacial anchorage of lipid multilayers.
• Understanding these interfacial properties offers a rational approach to optimizing phospholipid-based emulsion formulations.