Localization of a FITC-labeled phosphorothioate oligodeoxynucleotide in the skin after topical delivery by iontophoresis and electroporation.

PURPOSE: The aim of this study was to verify the hypothesis that the application of high voltage to the skin enhances both stratum corneum and keratinocyte permeability. Therefore, the transport of FITC labelled phosphorothioate oligonucleotides (FITC-PS) administered by passive diffusion, iontophoresis or electroporation was localized. METHODS: Fluorescent microscopy and laser scanning confocal microscopy were used to visualize the FITC-PS transport at the tissue and cell level respectively in hairless rat skin after electroporation (5 x (200 V approximately 500 ms) or iontophoresis (same amount of charges transferred). RESULTS: FITC-PS did not penetrate the viable skin by passive diffusion. Molecular transport in the skin upon electroporation or iontophoresis was localized and implied mainly hair follicles for iontophoresis. In the stratum corneum, the pathways for FITC-PS transport were more transcellular during electroporation and paracellular during iontophoresis. FITC-PS were detected in the nucleus of the keratinocytes a few minutes after pulsing. In contrast, iontophoresis did not lead to an uptake of the oligomer. CONCLUSIONS: The internalization of FITC-PS in the keratinocytes after electroporation confirms the hypothesis and suggests that electroporation, which allows both efficient topical delivery and rapid cellular uptake of the oligonucleotides, might be useful for antisense therapy of epidermal diseases