Molecular-level characterization of lipid membrane electroporation using linearly rising current.

We present experimental and theoretical results of electroporation of small patches of planar lipid bilayers by means of linearly rising current. The experiments were conducted on ~120-μm-diameter patches of planar phospholipid bilayers. The steadily increasing voltage across the bilayer imposed by linearly increasing current led to electroporation of the membrane for voltages above a few hundred millivolts. This method shows new molecular mechanisms of electroporation. We recorded small voltage drops preceding the breakdown of the bilayer due to irreversible electroporation. These voltage drops were often followed by a voltage re-rise within a fraction of a second. Modeling the observed phenomenon by equivalent electric circuits showed that these events relate to opening and closing of conducting pores through the bilayer. Molecular dynamics simulations performed under similar conditions indicate that each event is likely to correspond to the opening and closing of a single pore of about 5 nm in diameter, the conductance of which ranges in the 100-nS scale. This combined experimental and theoretical investigation provides a better quantitative characterization of the size, conductance and lifetime of pores created during lipid bilayer electroporation. Such a molecular insight should enable better control and tuning of electroporation parameters for a wide range of biomedical and biotechnological applications.