Dependence on pulse duration and number of tumor cell apoptosis by nanosecond pulsed electric fields

Tumor cell apoptosis by using nanosecond pulsed electric fields (nsPEF) has a great potential in clinical tumor treatment. It is difficult to find the appropriate parameters of nsPEF which can induce substantial apoptotic tumor cells because of selectivity between apoptosis and parameters of pulse number and pulse duration. To obtain the optimum parameters of nsPEF which can achieve large proportion of apoptotic tumor cells, nsPEF with different parameters (Electric field intensity of 45 kV/cm; pulse durations are 50, 100 and 200 ns respectively; pulse numbers are 10, 30, 60 and 80, respectively; repetition frequency of 1 Hz) were performed on SKOV3 cells. The experimental results of both Annexin-V/PI staining and DNA ladder gel electrophoresis indicated that apoptosis of tumor cells was pulse duration and number-dependent. With constant electric field intensity of 45 kV/cm, nsPEF of 100 ns duration and 30 pulses caused substantial tumor cell apoptosis with few necrotic cells and maximum caspase-3 activation.