Dye Transport through Bilayers Agrees with Lipid Electropore Molecular Dynamics

Area of Science:

• Biophysics
• Cell Biology
• Computational Biology

Background:

• Electroporation is a key biomedical technique for molecule delivery into cells.
• Current electroporation protocols often rely on empirical optimization due to poorly understood mechanisms.
• Linking theoretical models to experimental data is challenging due to numerous fitting parameters.

Purpose of the Study:

• To investigate the consistency between atomistic molecular dynamics (MD) simulations and experimental observations of cell membrane electroporation.
• To elucidate the underlying mechanisms and timescales of electropore formation and closure in phospholipid bilayers.
• To compare electroporation dynamics in a simplified model system (GUVs) with known cellular responses.

Main Methods:

• Utilized time-resolved, atomistic molecular dynamics (MD) simulations of phospholipid bilayers subjected to electric fields.
• Employed giant unilamellar vesicles (GUVs) to study membrane electroporation, measuring molecular transport via calcein dye entry.
• Varied electric pulse durations and interpulse intervals (nanosecond scale) to probe transport kinetics and electropore lifetimes.

Main Results:

• MD simulations indicated lipid bilayer electropore lifetimes in the range of 10-50 nanoseconds.
• Molecular transport in GUVs was additive for interpulse intervals of 50 ns but not 5 ns, aligning with simulated electropore lifetimes.
• Discrepancies were observed between GUV permeabilization kinetics and published data for ultrashort electric field exposure in cells.

Conclusions:

• The study provides experimental evidence supporting MD simulations of electroporation in simplified membrane models.
• Electropore lifetimes are a critical factor in understanding molecular transport during pulsed electric field applications.
• Cellular electroporation likely involves additional factors beyond simple lipid bilayer dynamics, necessitating further investigation.