Undulation instability in a bilayer lipid membrane due to electric field interaction with lipid dipoles

TL;DR

This paper models how electric fields induce undulation instability in bilayer lipid membranes by coupling membrane dipoles and tilt, revealing conditions that increase pore formation likelihood.

Contribution

It introduces a phenomenological free energy model capturing the membrane's response to electric fields, emphasizing the role of dipole-tilt coupling and dipolar order.

Findings

Membrane becomes unstable through buckling modes.

Thickness fluctuations increase pore formation probability.

Instability depends on dipole-tilt coupling strength.

Abstract

Bilayer lipid membranes [BLMs] are an essential component of all biological systems, forming a functional barrier for cells and organelles from the surrounding environment. The lipid molecules that form membranes contain both permanent and induced dipoles, and an electric field can induce the formation of pores when the transverse field is sufficiently strong (electroporation). Here, a phenomenological free energy is constructed to model the response of a BLM to a transverse static electric field. The model contains a continuum description of the membrane dipoles and a coupling between the headgroup dipoles and the membrane tilt. The membrane is found to become unstable through buckling modes, which are weakly coupled to thickness fluctuations in the membrane. The thickness fluctuations, along with the increase in interfacial area produced by membrane buckling, increase the probability of localized membrane breakdown, which may lead to pore formation. The instability is found to depend strongly on the strength of the coupling between the dipolar headgroups and the membrane tilt as well as the degree of dipolar ordering in the membrane.