THE REDUCTION IN ELECTROPORATION VOLTAGES BY THE ADDITION OF A SURFACTANT TO PLANAR LIPID BILAYERS

The effects of a nonionic surfactant, octaethyleneglycol mono n-dodecy l ether (C12E8), on the electroporation of planar bilayer lipid membra nes made of the synthetic lipid 1-pamitoyl 2-oleoyl phosphatidylcholin e (POPC), was studied. High-amplitude (similar to 100-450 mV) rectangu lar voltage pulses were used to electroporate the bilayers, followed b y a prolonged, low-amplitude (similar to 65 mV) voltage clamp to monit or the ensuing changes in transmembrane conductance. The electroporati on thresholds of the membranes were found for rectangular voltage puls es of given durations. The strength-duration relationship was determin ed over a range from 10 mu s to 10 s. The addition of C12E8 at concent rations of 0.1, 1, and 10 mu M to the bath surrounding the membranes d ecreased the electroporation threshold monotonically with concentratio n for all durations (p < 0.0001). The decrease from control values ran ged from 10% to 40%, depending on surfactant concentration and pulse d uration. For a 10-mu s pulse, the transmembrane conductance 150 mu s a fter electroporation (G(150)) increased monotonically with the surfact ant concentration (p = 0.007 for 10 mu M C12E8). These findings sugges t that C12E8 incorporates into POPC bilayers, allowing electroporation at lower intensities and/or shorter durations, and demonstrate that s urfactants can be used to manipulate the electroporation threshold of lipid bilayers.