822. Efficient Delivery of Plasmid DNA to Murine Skin Using In Vivo Electroporation1

The easy accessibility of skin makes it an excellent target for gene transfer protocols. Cutaneous diseases can be treated directly. In addition, the skin is a suitable target for delivering proteins directly to the circulation for systemic therapy. To be able to fully take advantage of skin as a target for gene transfer, it is important to establish an efficient and reproducible delivery system. Electroporation as a tool for the delivery of plasmid DNA is a strong candidate to meet these delivery criteria. Previously, we demonstrated that electroporation could be used to deliver plasmid DNA to the skin and confirm that localized delivery can also result in increased serum levels of a specific protein. In addition, it was shown that several factors needed to be considered when developing an electroporation delivery protocol including electrode configuration, pulse width, field strength and DNA concentration. More recently, we have been determining optimal delivery conditions using a plasmid encoding luciferase (pLUC). Various EP parameters for delivery to murine skin were examined and included over 50 different combinations. Most of the conditions showed an increase of expression over injection alone. There were 5 combinations that showed the largest increase when compared to injection alone. With respect to plasmid DNA concentration, the highest reproducible expression was seen with 2 μg/μl. Using a plasmid encoding for green fluorescent protein, an efficiency of > 30% was obtained. The effect of multiple applications was also examined. The procedure was evaluated by using the “optimal” electroporation conditions with pLUC at either 2 or 10 days apart. Peak expression could be maintained at a later time point than with a single treatment but the overall length of expression was not extended. This protocol was also repeated using a secreted protein as a marker as well. The results presented here demonstrate that electroporation can be used to augment the efficiency of direct injection of plasmid DNA to skin.