Evaporation-induced monolayer compression improves droplet interface bilayer formation using unsaturated lipids

Area of Science:

• Biophysics
• Materials Science
• Membrane Biophysics

Background:

• Droplet interface bilayers (DIBs) are crucial model membranes.
• Forming stable DIBs with unsaturated lipids like DOPC and POPC is challenging.
• Existing methods have low success rates for these specific lipids.

Purpose of the Study:

• To develop a reliable method for forming DIBs with difficult unsaturated lipids.
• To investigate the behavior of unsaturated lipid monolayers at oil-water interfaces.
• To enable quantitative characterization of unsaturated lipid DIB properties.

Main Methods:

• A simple evaporation technique to condition lipid monolayers on droplets.
• Pendant drop tensiometry to study interfacial tension and monolayer packing.
• Langmuir compression isotherms to quantify area per lipid.
• DIB formation and electrical property measurements.

Main Results:

• Evaporation technique increased DIB formation success rates for DOPC and POPC from <10% to ~100%.
• DOPC and POPC monolayers do not spontaneously achieve tight packing.
• Droplet evaporation leads to tighter monolayers and lower interfacial tension.
• Evaporation reduced area per lipid by 6%-16% for DOPC and POPC.

Conclusions:

• The implemented evaporation method is highly effective for forming stable DIBs with unsaturated lipids.
• This technique overcomes previous limitations in creating model membranes with DOPC and POPC.
• The improved DIBs allow for detailed characterization of unsaturated lipid membrane properties.