Effect of electroporation and recovery medium pH on cell membrane permeabilization, cell survival and gene transfer efficiency in vitro.

Electroporation is a method which uses an adequate number of electric pulses of enough amplitude, duration and number applied to cells, thus inducing transient permeabilization of the cell membrane. Due to possibility that microenvironment in applications of in vivo electroporation is slightly acidic, we studied the effects of slightly acidic electroporation and recovery medium. We observed no difference in the permeabilization threshold, detected by propidium iodide, of cells which were electroporated and allowed to recover in growth (pH 7.8) or acidic (pH 6.5) medium. In contrast, statistically significant difference was observed in survival of cells that were exposed to pulse amplitudes greater than permeabilization threshold. Survival of cells was greater if acidic electroporation and recovery medium were used, but acidic extracellular pH decreased gene electrotransfer efficiency. We also observed differences in morphology between cells that were electroporated and left to recover in growth medium and cells that were electroporated and left to recover in acidic medium. Our results imply that slightly acidic extracellular pH allows more efficient repair of damage that is induced on cell membrane during electroporation with high pulse amplitudes.