Cholesterol-Controlled Interaction of Ionic Liquids with Model Cellular Membranes

Area of Science:

• Biophysical chemistry
• Membrane biophysics
• Materials science

Background:

• Ionic liquids (ILs) show promise as antimicrobial agents.
• Understanding ILs' effects on human cell membranes is crucial for safety.
• Cholesterol is a key component of human cell membranes.

Purpose of the Study:

• Investigate the impact of an imidazolium-based IL on model membranes with and without cholesterol.
• Determine how cholesterol influences the interaction between ILs and lipid bilayers.
• Assess the potential for ILs to act as antimicrobials without harming human cells.

Main Methods:

• Area-surface pressure isotherms of lipid monolayers at the air-water interface.
• Measurement of lipid monolayer rigidity and elasticity.
• X-ray reflectivity studies on stacked lipid bilayers.

Main Results:

• ILs reduce the area per sphingomyelin lipid, an effect diminished by cholesterol.
• ILs decrease the rigidity of cholesterol-free monolayers but increase elasticity in cholesterol-containing condensed phases.
• X-ray reflectivity reveals IL-induced phase separation and thinner membranes in cholesterol-free bilayers, less so in cholesterol-containing ones.

Conclusions:

• ILs may deform bacterial membranes by forming thinner, phase-separated domains.
• Cholesterol in human cell membranes can restrict IL insertion, potentially preventing harmful effects.
• This suggests a selective antimicrobial action of ILs, sparing human cells.