Apoptosis by direct electric field (DEF) and nanosecond pulsed electric field (nsPEF) in tumor cells and tumor tissues

摘要

Pulsed electric field induces cell fusion, electroporation on biological cells. Electroporation them occurs with pulse durations in the order of 0.1-10 ms and electric fields of kV/cm, depending on the cell type and suspension media. Nanosecond pulsed electric fields(nsPEF) are normally with durations of about 1-300 ns with the electric field strength less than 300 kV/cm. The nsPEF is recognized to induce apoptosis in cells by affecting intracellular structures. Apoptosis is expressed in a series of natural enzymatic reactions for the natural elimination of unhealthy, genetically damaged, or otherwise aberrant cells that are not needed or not advantageous to the well-being of the organism. Its markers involve cell shrinkage, activation of intracellular caspase proteases, externalization of phosphatidylserine at the plasma membrane, and fragmentation of DNA. Direct electric fields(DEF) using direct current have been exploited recently to investigate its effects on tumor cells and tissues, but the mechanism of DEF has not been exhibited clearly other than by electroosmosis or pH changes. We show that DEF induces apoptosis in tumor cells cultured as indicated by cell shrinkage, DNA fragmentation and tumor suppression. The DEF effects depend upon current intensity, level of potential and expose time of cell to DEF We also exhibit that the inhibition of tumor growth(anti-tumor effects) correlates incident dose (electrical charge delivered) into tumor tissues in formula. Total electric charge will also be compared in the two cases of nsPEF and DEF approach.