Parameters controlling topical delivery of oligonucleotides by electroporation

Electroporation, using high voltage electrical pulses has been recognized as a powerful method for delivering macromolecules such as DNA and proteins in cells, or smaller molecules through the skin. Transdermal electroporation could combine targeted delivery of drugs to the skin and permeabilization of skin cells, suggesting that electroporation could be an interesting alternative for topical delivery of oligonucleotides. This work is devoted to the determination of the electroporation parameters that allow optimal delivery of oligonucleotides to the viable tissues of hairless rat skin in vitro. Phosphorothioate derivatives were preferred to the phosphodiester congeners as the former were found to be much less degraded when extracted from the tissues. Long duration (100-500 ms)--medium voltage (100-200 V)--exponentially decaying pulses appeared to be the best conditions for delivering oligonucleotides to the skin. The oligonucleotide quantity permeating the viable tissues of the skin was controlled by the selection of the electrical parameters of the pulses (voltage, pulse time and number of pulses) or by the ON concentration in the donor compartment. After delivery by electroporation, therapeutic levels of oligonucleotides were reached in the viable tissues of the skin (above 1 microM or 10 microM in intact or stripped skin respectively). Taken together, our results show that electroporation could be an interesting method for the delivery of oligonucleotides to the skin.