Determination of the electroporation onset of bilayer lipid membranes as a novel approach to establish ternary phase diagrams: example of the L-α-PC/SM/cholesterol system

We present a detailed study to the effect of the three main lipid consistent of cell membranes on the electroporation process. The lipid matrix of cell membranes contains phospholipids belonging to two main classes, glycero- and sphingolipids, as well as cholesterol. The lipid matrix can exist in different phases, liquid disordered (l_d), liquid ordered (l_o) and eventually solid (s_o), or even a combination of those. The precise phase composition of a membrane depends on its molecular content and, more specifically, on the presence and amount of cholesterol. This in turn dictates the membrane properties. We specifically study the resistance of membranes to the process of electroporation and relate this to the membrane phase composition. For membranes prepared from various mixtures of a glycerolipid (Heart PC (L-α-PC)), a sphingolipid (Egg SM (SM)) and cholesterol (Ch), introduced in various ratios, the threshold voltage for electroporation (V_th) is measured. Binary mixture (L-α-PC/Ch; SM/Cholesterol; L-α-PC/SM) and L-α-PC/SM/Ch ternary mixtures are successively employed. For all binary and ternary systems, we measure dramatic changes in V_th as a function of the membrane molecular composition (see figure 1), and the variation patterns of V_th with are successfully correlated with the membrane phase composition. Interestingly, the measure of the electroporation onset can be employed as a novel methodology to establish ternary phase diagrams, and this is illustrated with l-α-PC/SM/cholesterol systems (see figure 1). This phase diagram correlates well with other diagrams found in literature.

A detailed explanation can be found in the research paper in Soft Matter, DOI: 10.1039/C0SM00181C: http://pubs.rsc.org/en/Content/ArticleLanding/2010/SM/C0SM00181C

For more information, contact Iris van Uitert: i.vanuitert@ewi.utwente.nl