Apoptosis Induction Effects of Steep Pulsed Electric Fields (SPEF) on Human Liver Cancer Cell SMMC-7721 in vitro

To research the apoptosis effects of steep pulsed electric fields (SPEF) on human liver cancer cell SMMC-7721
in vitro
, this paper studied phosphatidylserine (PS) externalization detection utilizing flow cytometry, real-time change of mitochondrial transmembrane potential (Ωψ
_m
) using confocal laser scanning microscope (CLSM) and DNA fragmentation assay by agarose gel electrophoresis. The experiment results by flow cytometry showed that μsSPEF (SPEF with electric field intensity of 200V/cm and duration of 1.3μs) effectively (P<0.05) induced PS externalization but μsSPEF (SPEF with electric field intensity of 600V/cm and duration of 100ns) did not (P>0.05). On the contrary, nsSPEF induced Ωψ
_m
decrease and DNA fragmentation more notably than μsSPEF. These results indicate that SPEF can distinctly induce apoptosis and the effects are electric field intensity/pulse duration-dependent. Theoretically calculation showed that temperature increase of cell solutions for treated groups exposed to SPEF was less than 1.3K without regard to heat dissipation. Multi-shelled dielectric cell model and frequency spectrum analysis showed that μsSPEF contained abundant low frequency components which mainly acted on plasma membrane, whereas μsSPEF contained plentiful high frequency components which permeated plasma membrane and mainly affected on intracellular organelle.