Bioelectrorheological model of the cell. 4. Analysis of the extensil deformation of cellular membrane in alternating electric field

Permeabilizing Cell Membranes with Electric Fields

The biological impact of exogenous, alternating electric fields (AEFs) and direct-current electric fields has a long history of study, ranging from effects on embryonic development to influences on wound healing. In this article, we focus on the application of electric fields for the treatment of cancers. In particular, we outline the clinical impact of tumor treating fields (TTFields), a form of AEFs, on the treatment of cancers such as glioblastoma and mesothelioma. We provide an overview of the standard mechanism of action of TTFields, namely, the capability for AEFs (e.g., TTFields) to disrupt the formation and segregation of the mitotic spindle in actively dividing cells. Though this standard mechanism explains a large part of TTFields' action, it is by no means complete. The standard theory does not account for exogenously applied AEFs' influence directly upon DNA nor upon their capacity to alter the functionality and permeability of cancer cell membranes. This review summarizes the current literature to provide a more comprehensive understanding of AEFs' actions on cell membranes. It gives an overview of three mechanistic models that may explain the more recent observations into AEFs' effects: the voltage-gated ion channel, bioelectrorheological, and electroporation models. Inconsistencies were noted in both effective frequency range and field strength between TTFields versus all three proposed models. We addressed these discrepancies through theoretical investigations into the inhomogeneities of electric fields on cellular membranes as a function of disease state, external microenvironment, and tissue or cellular organization. Lastly, future experimental strategies to validate these findings are outlined. Clinical benefits are inevitably forthcoming.

Low dose, alternating electric current inhibits growth of prostate cancer

BACKGROUND

A number of minimally invasive technologies exist for the treatment of prostate cancer (CaP), each with their associated morbidities. We sought to test the efficacy of low dose alternating electric current (LDAEC) to inhibit CaP growth in a preclinical setting and determine its effect on normal tissue.

METHODS

In the first study, two power settings, 15 or 25 mA of current, and two treatment times, 15 or 60 min, were evaluated in C4-2B CaP xenografts. In the second study, power was regulated to maintain an intra-tumoral temperature of <or=45 degrees C in C4-2B and LuCaP 35 tumors. In both studies, tumor volume, serum PSA levels, survival and histology were analyzed. In a third study, LDAEC was applied to mice hamstrings with evaluation of gait and histology.

RESULTS

The most effective tumor volume reduction in the first study was seen with tumors treated with 25 mA for 15 min (62 +/- 9.4% decrease, P = 0.001). Longer treatment time did not enhance treatment effect. Using 45 degrees C to govern delivery of LDAEC resulted in a near 100% reduction in tumor volume in 8/10 mice with C4-2B tumors (P < 0.001) with similar inhibition of LuCaP 35 tumors (P = 0.01). This treatment, although resulting in skeletal muscle necrosis, did not affect nerves, smooth muscle and blood vessels.

CONCLUSION

LDAEC demonstrates efficacy against C4-2B and LuCaP 35 CaP xenografts while causing no harm to nerves and blood vessels. These results warrant further investigations into the use of LDAEC as a treatment for CaP.

Transient dielectro-deformations of erythrocyte governed by time variation of cell ionic state

The possibility is shown to monitor the transient ionic state and volume of erythrocyte suspended in low ionic strength solution (LISS) by registration of the dielectro-deformation (DD) of a cell. The adequate theoretical basis is developed. Possible registration modes are considered analytically and numerically using the theory of dielectro-deformation of erythrocytes developed previously.

Electrorheological modeling of the permeabilization of the stratum corneum: theory and experiment

Experimentally observed changes in the conductivity of skin under the influence of a pulsing electric field were theoretically analyzed on the basis of a proposed electrorheological model of the stratum corneum (SC). The dependence of relative changes in conductivity on the amplitude of electric field and timelike parameters of applied pulses or pulse trains have been mathematically described. Statistical characteristics of phenomena of transient and long-term electroporation of SC were taken into consideration. The time-dependent decreases of skin resistance depicted by the models were fitted to experimental data for transient and long-term skin permeabilization by electric pulses. The results show two characteristic times and two spectra of characteristic energies for transient and long-term permeabilizations. The rheological parameters derived from the fittings agreed with those reported elsewhere for biological membranes.

Bioelectrorheological model of the cell. VI. Experimental verification of the rheological model of cytoplasmic membrane

The susceptibility of the Neurospora crassa (slime) cellular membrane to electroporation and electrodestruction in an alternating electric field was further investigated. The results were analyzed according to the dynamic rheological model of the cytoplasmic membrane. Based on an analytical description of membrane susceptibility to electroporation, the rheological parameters of the foregoing process in N. crassa cellular membrane were found: they closely resemble those previously determined for the membranes' destruction. This suggests that both processes are temporally related and are induced within the same structures of the membrane. The dependence of the destruction of the membrane on the time of application and the frequency of the electric field was theoretically predicted and experimentally confirmed.

Bioelectrorheological model of the cell. 5. Electrodestruction of cellular membrane in alternating electric field

Recently proposed analysis of the extensil stress developed in a cellular membrane subjected to an alternating electric field (Pawłowski, P., and M. Fikus, 1993. Bioelectrorheological model of the cell. 4. Analysis of the extensil deformation of the membrane in an alternating field. Biophys. J. 65:535-540) was applied in calculations of extensil stress threshold values, sigma eo[d], producing experimentally observed electrodestruction of cells within the frequency range of 7 x 10(1) - 3 x 10(5) Hz. It was shown that the susceptibility (s[d] = 1/sigma eo[d]), of the membrane to this process varies with field frequency and depends on the type of cells. Electrodestruction is facilitated in the 10(5)-Hz field. A rheological hypothesis explaining the experimentally observed dependence of membrane stability on electric field frequency was proposed and successfully tested for two other phenomena: electroporation and electrofusion.