Inter-pulse interval between rectangular voltage pulses affects electroporation threshold of artificial lipid bilayers

This paper describes experiments that determine how the inter-pulse interval between rectangular pulses in a train of pulses alters the threshold of electroporation of 1-pamitoyl 2-oleoyl phosphatidycholine bilayer lipid membranes. The bilayers were exposed to a train of sixteen 100-micros duration pulses. Threshold voltage and the sequence number of the pulse in the train, where onset of the electroporation occurred, were recorded for six inter-pulse intervals (infinity, 1000 micros, 100 micros, 10 micros, 1 micros, 0 micros). The threshold voltage of the pulse train decreased linearly with the logarithm of the inter-pulse interval. When the inter-pulse interval was 1 microm, electroporation threshold dropped to that of a single pulse with duration 1600 micros (equal to the sum of all pulse durations in the train). In this case, the occurrence of bilayer rupture was almost equally frequent for all pulses in the train. When the inter-pulse interval between the pulses exceeded 1 micros, the influence of the previous pulse on the response to the following pulse declined. It became more likely that the bilayer ruptured during the first half of the train. These experimental observations suggest that a train of pulses applied with short inter-pulse interval (less than 1 ms) can lower the electroporation threshold of bilayer lipid membranes.