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1 May 2002 Electrically Enhanced Percutaneous Delivery Of δ-Aminolevulinic Acid Using Electric Pulses and a DC Potential
Patricia G. Johnson, Sek Wen Hui, Allan R. Oseroff
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Selectivity of photodynamic therapy can be improved with localized photosensitizer delivery, but topical administration is restricted by poor diffusion across the stratum corneum. We used electric pulses to increase transdermal transport of δ-aminolevulinic acid (ALA), a precursor to the photosensitizer protoporphyrin IX (PpIX). ALA-filled electrodes were attached to the surface of excised porcine skin or the dorsal surface of mice. Pulses were administered and, in some in vivo cases, a continuous DC potential (6 V) was concomitantly applied. For in vitro 14C ALA penetration, 10 μm layers parallel to the stratum corneum were assayed by liquid scintillation analysis, and 10 μm cross sections were examined autoradiographically. As the electrical dose (voltage × frequency × pulse width × treatment duration) increased, there was an increase in penetration depth. In vivo delivery was assayed by measuring the fluorescence of PpIX in skin samples. A greater than two-fold enhancement of PpIX production with electroporative delivery was seen versus that obtained with passive delivery. Superimposition of a DC potential resulted in a nearly three-fold enhancement of PpIX production versus passive delivery. Levels were higher than the sum of PpIX detected after pulse-alone and DC-alone delivery. Electroporation and electrophoresis are likely factors in electrically enhanced delivery.

Patricia G. Johnson, Sek Wen Hui, and Allan R. Oseroff "Electrically Enhanced Percutaneous Delivery Of δ-Aminolevulinic Acid Using Electric Pulses and a DC Potential," Photochemistry and Photobiology 75(5), 534-540, (1 May 2002).<0534:EEPDOA>2.0.CO;2
Received: 18 September 2001; Accepted: 1 February 2002; Published: 1 May 2002

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