Mixed DPPC/DPPG monolayers at very high film compression.

Area of Science:

• Surface science
• Biophysics
• Materials science

Background:

• Lung surfactant is crucial for respiratory function, composed of lipids and proteins.
• Maintaining stable lung surfactant films is vital for preventing alveolar collapse.
• The constrained sessile drop assembly (ADSA-CSD) offers advantages for studying thin films.

Purpose of the Study:

• To investigate the role of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) mixtures in lung surfactant.
• To characterize the impact of varying DPPC/DPPG ratios on film properties using ADSA-CSD.
• To understand the molecular interactions governing stable film formation and surface activity.

Main Methods:

• Utilized the advanced sessile drop assembly (ADSA-CSD) technique.
• Prepared mixed DPPC/DPPG monolayers at various molar ratios (90/10 to 50/50).
• Measured compression isotherms, ultimate collapse pressure, film elasticity, and hysteresis at 24°C.

Main Results:

• Low DPPG content (≤20%) maintained high collapse pressure (~70.5 mJ/m²), similar to pure DPPC.
• Increasing DPPG to 40% caused a slight decrease in collapse pressure.
• High DPPG content (≥50%) sharply reduced collapse pressure (~59.9 mJ/m²), similar to pure DPPG.
• Film elasticity and hysteresis changed with varying DPPC/DPPG ratios.

Conclusions:

• DPPG content significantly influences the stability and surface activity of DPPC-based films.
• The ADSA-CSD technique is effective for characterizing mixed monolayers relevant to lung surfactant.
• Understanding DPPC/DPPG interactions is key to developing effective lung surfactant therapies.