[Research progress of nanosecond pulsed electric field applied to intracellular electromanipulation].

In recent years, many experts have done some researches on experiment and mechanism of intracellular electromanipulation (IEM) under nanosecond pulsed electric field (nsPEF). The experiment results have shown that nsPEF could not induce electroporation of cell membrane, but could induce intracellular effects such as apoptosis, calcium release, enhancement of gene expression, and fragmentation of DNA and chromosome. In order to account for the phenomenon, researchers believe that when the pulse width of the pulsed electric field is larger than the charging time of plasma membrane, the pulsed electric field mainly targets on the outer membrane of cell; and that the effect of the pulsed electric field on nucleus and nuclear membrane increases with the decrease of the pulse width. It is also believed that the effect of electroporation changes from the outer membrane to intracellular electromanipulation when the pulse width decreases to a value being smaller than the charging time of plasma membrane.

Effects of steep pulsed electric fields (SPEF) on mitochondrial transmembrane potential of human liver cancer cell.

Mitochondrial plays an important role in apoptosis, and measuring the change of mitochondrial transmembrane potential (delta psi m) is a useful method for apoptosis. Exposing human liver cancer cell SMMC-7721 dyed with Rhodamine 123 to steep pulsed electric fields (SPEF), this paper observed the real-time change of delta psi m using laser scanning confocal microscope (LSCM) to study the apoptosis effect of SPEF. The experiment results showed that delta psi m decreased gradually in process of exposing to SPEF, SPEF with higher voltage (600V) and shorter width (100ns) could cause a quicker decrease than SPEF with lower voltage (200V) and longer width (1.3mus). Such phenomenon kept up even after canceling SPEF, this may lead to collapse of delta psi m and induce apoptosis with tremendous possibilities. The experiment results of flow cytometry (SMMC-7721 dyed with Annexin V-FITC) approved that SPEF could induce apoptosis markedly (P<0.01); SPEF with lower voltage (200V) and longer width (1.3mus) could induce apoptosis more effectively (P<0.01) than SPEF with higher voltage (600V) and shorter width (100ns). These experiment results supply possible mechanism and parameter selection basis for tumor treatment using SPEF.

Analysis of Transmembrane Potentials Induced by Pulsed Electric Field with Different Durations Based on Five-shelled Dielectric Model of Cell.

In order to account for the influence of subcellular organelles on transmembrane potential, five-shelled dielectric model of spherical cell was developed in this paper. And the calculation method of transmembrane potential induced by any pulsed electric field (PEF) was put forward. Thus the effects of different pulse duration on transmembrane potentials of cell membrane and nuclear membrane were also analyzed. It is shown that there is a strong relationship between the amplitude and waveform of transmembrane potential and pulse duration. PEF with shorter duration can reaches into the cell easily, thus with shorter duration pulses, transmembrane potential of nuclear membrane is increasing and close to that of cell membrane. So PEF with shorter duration will bring on some important biological effects, such as electroporation or apoptosis.