Understanding interactions of plasticisers with a phospholipid monolayer

Area of Science:

• Biochemistry
• Materials Science

Background:

• Diethylhexyl phthalate (DEHP) is crucial for blood bag preservation due to its ability to extend red blood cell viability.
• Butanoyl trihexyl citrate (BTHC) is an alternative plasticizer used in pediatric blood bags but shows lower efficacy in stabilizing blood cells.
• Understanding plasticizer-lipid interactions is key to explaining differences in blood cell stabilization and potential bioaccumulation.

Purpose of the Study:

• To investigate the interactions between the plasticizers DEHP and BTHC with the phospholipid DMPC.
• To elucidate the molecular mechanisms behind DEHP's superior blood cell stabilization properties compared to BTHC.
• To assess differences in plasticizer incorporation, bioaccumulation, and interfacial behavior.

Main Methods:

• Formation and analysis of mixed monolayers of DMPC with either DEHP or BTHC using Langmuir troughs.
• Measurement of surface pressure/area isotherms to determine monolayer properties.
• Neutron reflection studies to analyze the composition and structure of the mixed lipid layers.

Main Results:

• Both DEHP and BTHC can be incorporated into DMPC monolayers up to a certain limit (40-60 mol% for DEHP, 20-40 mol% for BTHC).
• Beyond these limits, excess plasticizer is selectively removed from the interface at high surface pressures.
• DEHP integrates more effectively into DMPC monolayers (50-100 Ų per molecule) compared to BTHC (65-120 Ų per molecule).

Conclusions:

• DEHP exhibits better compatibility and packing within DMPC lipid monolayers than BTHC.
• The superior fit of DEHP in lipid bilayers likely contributes to its enhanced effectiveness in stabilizing blood cells.
• These findings provide insights into the design of improved plasticizers for blood storage applications.