Delayed poration after ultrashort electric pulses on Jurkat cell G Chen and K Daly School of Electronics and Computer Science University of Southampton United Kingdom *Email: gc@ecs.soton.ac.uk Abstract : Electrical properties of cancer cells have been studied widely to understand cancer. The increase in electrical conductivity of Jurkat cell suspension after ultrashort electric pulses has been considered as an important phenomenon of the interaction between pulsed electric field and cancer cells. Experimental evidence showed that such an interaction may result in delayed poration. In this paper an attempt has been made to find probability distribution function of poration after ultrashort electric pulses. The conductivity data collected from nanosecond pulse electroporation of Jurkat cancer cells is analysed to form a probability distribution function for pore formation after nanosecond electric field pulse. It has been found that the parameter in the function depends on pulse characteristics such as pu lse magnitude, pulse width and number of pulses. 1 INTRODUCTION Understanding cancer has been an objective of molecular and cellular biologists for many years. A variety of different techniques have been developed. One such technique is to use a pulsed electric field to control the function of biological cells via electroporation process. Electroporation is the term used to describe the appearance of pores in cell membrane due to an elevated transmembrane electric potential caused by an applied pulse electric field. Typically, it occurs with pulse width on the order of 0.1-10 ms and electric field on the order of kV/cm. It is found that such pulses promote transient membrane poration and cell survival. Various applications Q1Q in biology, biotechnology and medicine have been found to utilize such interaction. In recent years, intensive research Q2-3Q has been carried out using ultra short electric pulses. As the pulse width decreases, it has been experimentally demonstrated that interaction with plasma membrane decreases while interaction with intracellular structure increases. Hypothesis has been made that the short pulse mainly interacts with the nuclear membrane. Modelling work has been carried out to understand the mechanisms Q4Q. The phenomenon raises the possibility that ultra short electric pulse could be used to induce apoptosis in mammalian cells by affecting intracellular structures Q5Q. Our earlier result on electrical conductivity of Jurkat cell suspension after ultrashort electric pulses indicated a gradual increase Q6Q. This may be related to the interaction between the pulses and nuclear membrane via a delayed poration Q7 Q. In this paper conductivity data collected from nanosecond pulse electroporation of Jurkat cancer cells is analysed to form a probability distribution function for pore formation after nanosecond pulse electroporation. 2 EXPERIMENTAL RESULTS The increase in electrical conductivity of Jurkat cell suspension has been reported Q6Q. The detailed cell preparation is crucial for the experiment. The Jurkat cell line used in the experiment is derived from human T- cell leukaemia. The cells were cultured in RPMI-1640 Medium and centrifuged three times and then washed with sucrose/glucose buffer. Finally, the cells were adjusted to a 5% concentration. Sufficient cell suspension was transferred to a gene pulser cuvette for pulsing. After pulsed electric field application, we transferred a small amount to the electrode chamber for conductivity measurement. The cell viability was checked occasionally to ensure that pulsed electric field did not induce significant cell death. As the conductivity is temperature sensitive the sample temperature was maintained at 25 o C by using a thermostat. Figure 1 summaries the conductivity results obtained from Jurkat cell suspension after various electric pulses. It can be seen that single 10ns and 150 kV/mm pulse have very minor effect on the suspension conductivity. Therefore this set of result will not be dealt with in the present paper. For the other results it has been noticed that magnitude, pulse duration and number of pulses seem to have significant influence on the conductivity. The change in conductivity may be represented by ) ( max 0 t F σ σ σ ∆ + = (1) where 㰰 o is the conductivity of suspension before the application of electric pulse, 㥀㰰 max is the difference between stable conductivity after electric pulses and 㰰 o , F(t) the cumulative function reflecting the interaction between electric pulses and cells. The origin of conductivity is ions present in the cell suspension. The increase in conductivity can be attributed to the extra ions released from cells during poration. As there are XV International Symposium on High Voltage Engineering th University of Ljubljana, Elektroinštitut Milan Vidmar, Ljubljana, Slovenia, August 27-31, 2007 T3-151.pdf 1