Interaction of anionic/nonionic surfactant mixtures with phosphatidylcholine liposomes

Area of Science:

• Surfactant chemistry
• Liposome interactions
• Membrane biophysics

Background:

• Phosphatidylcholine liposomes are crucial in drug delivery.
• Understanding surfactant-lipid interactions is key to controlling drug release.
• Sodium dodecyl sulfate (SDS) and nonylphenol oxyethylenated (NP(EO)10) are common surfactants with distinct properties.

Purpose of the Study:

• To investigate the interaction mechanisms between mixed surfactants (SDS and NP(EO)10) and phosphatidylcholine liposomes.
• To quantify liposome permeability changes and bilayer solubilization.
• To determine the influence of surfactant composition on partitioning and critical concentrations.

Main Methods:

• Liposome preparation using phosphatidylcholine.
• Monitoring 5(6)-carboxyfluorescein (CF) release to assess permeability.
• Measuring static light scattering to evaluate bilayer solubilization.
• Calculating effective surfactant/lipid molar ratios (Re) and partition coefficients (K).

Main Results:

• Three key parameters (Re50%CF, ReSAT, ReSOL) were defined to characterize surfactant-lipid interactions.
• Partition coefficients (K) peaked at specific SDS mole fractions (XSDS), indicating complex partitioning behavior.
• Free surfactant concentrations remained below critical micelle concentrations (CMCs) at subsolubilizing levels.

Conclusions:

• The study elucidates the complex interplay between SDS and NP(EO)10 in altering liposome structure and function.
• The findings provide insights into optimizing surfactant mixtures for controlled drug release from liposomes.
• Understanding these interactions is vital for designing effective liposomal drug delivery systems.