One of the plausible reactions occurring during high-voltage pulses, which are used to electroporate the cells, is the oxidation of the metal ions of the anode resulting in the dissolution of the anode. In the case of the anode made from stainless steel, which is one of the most popular electrode materials, iron ions ( Fe²⁺ and Fe³⁺) are released from the anode. Here, this process and its consequences have been studied. A single square-wave electric pulse with the duration of 2 ms and the amplitude of 1.2 kV/cm increased the concentration of iron ions in solution by over 0.5 mM. Iron ions released from the anode behave as a Lewis acid and hydrolyze the water molecules in the solution, reducing the pH of a solution and might play a role in the changes of the medium conductivity. In addition, the roughness of the stainless steel anode increased progressively, in proportion with the total amount of the electric charge that had passed through the unit area of the electrode. The reduction of the viability of cells by iron ions has been demonstrated. The iron ions quench the fluorescence of anticancer drugs, which are used when photodynamic tumor therapy is combined with electroporation, such as porphyrin sulfonate and Adriamycin.

Here, theoretical relationships between the parameters of the electric pulse, which is necessary to porate the cell by electric pulse of various shapes, have been obtained. The theoretical curves were compared with the experimental relationships. Experiments were carried out with human erythrocytes, Chinese hamster ovary and mouse hepatoma MH-22A cells. The fraction of electroporated MH-22A cells was determined from the extent of the release of intracellular potassium ions and erythrocytes-from the extent of their hemolysis after long (20-24 h) incubation in 0.63% NaCl solution at 4°C. The dependence of the fraction of electroporated cells on the amplitude of the electric field pulse was determined for pulses with the duration from 95 ns to 2 ms. The shapes of theoretical dependencies are in agreement with experimental ones. The cell poration time depended on the intensity of the pulse: the shorter the pulse duration, the higher the electric field strength has to be. This dependence is much more pronounced for pulses . For example, if the pulse amplitude required to electroporate 50% of human erythrocytes increased from 1.0 to 1.76 kV/cm, when the duration of a square-wave pulse was reduced from 2 ms to 20 μs, it increased from 3 to 12 kV/cm, when the pulse duration was reduced from 950 to 95 ns. The relationships between the electric field strength required for electroporation and the frequency of the applied ac field were calculated for different pulselengths. It has been obtained that although the electric field strength is constant for frequencies but its value depends on the pulselength decreasing with increasing pulse duration. At higher frequencies, electric field strength is dependent on the frequency of the ac field.

High-voltage pulses applied to a cell suspension cause not only cell membrane permeabilization, but a variety of electrolysis reactions to also occur at the electrode–solution interfaces. Here, the cytotoxicity of a culture medium treated by a single electric pulse and the role of the iron ions in this cytotoxicity were studied in vitro. The experiments were carried out on mouse hepatoma MH-22A, rat glioma C6, and Chinese hamster ovary cells. The cell culture medium treated with a high-voltage pulse was highly cytotoxic. All cells died in the medium treated by a single electric pulse with a duration of 2 ms and an amplitude of just 0.2 kV/cm. The medium treated with a shorter pulse was less cytotoxic. The cell viability was inversely proportional to the amount of electric charge that flowed through the solution. The amount of iron ions released from the stainless steel anode (>0.5 mM) was enough to reduce cell viability. However, iron ions were not the sole reason of cell death. To kill all MH-22A and CHO cells, the concentration of Fe³⁺ ions in a medium of more than 2 mM was required.