Iontophoretic transport of oligonucleotides across human epidermal membrane: A study of the Nernst–Planck model

✍ Scribed by S. Kevin Li; Abdel-Halim Ghanem; Ching-Leou Teng; Gregory E. Hardee; William I. Higuchi

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 287 KB
• Volume: 90
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.1043

✦ Synopsis

The objective of this study was to investigate the transport behavior of a series of oligonucleotides with human epidermal membrane (HEM) and to examine the applicability of the modi®ed NERNST±PLANCK model to transdermal iontophoresis of these macromolecules. Iontophoretic transport experiments were ®rst carried out in a synthetic model membrane system (Nuclepore membranes) with a four-electrode potentiostat to examine the baseline modi®ed NERNST±PLANCK model. The modi®ed NERNST±PLANCK model derived from the Einstein relation and the Stokes±Einstein equation taken from previous work did not hold for the oligonucleotides. Results obtained in the Nuclepore studies were, however, consistent with predictions of the modi®ed NERNST±PLANCK model using the experimentally determined electromobilities and diffusion coef®cients. The electromobilities of the oligonucleotides (determined by capillary electrophoresis) were found to be more than a factor of two smaller than expected from the Einstein relation between electromobilities and diffusion coef-®cients (the latter determined in diffusion cell experiments). A correlation between these electromobilities and the theoretical electromobilities estimated by considering the effects of counterion binding and the effects of mobility reduction according to colloid theory was also observed. These results suggest that the modi®ed NERNST±PLANCK model predictions are satisfactory only when the electromobilities and the effective molecular size of the oligonucleotides are known and are used directly to predict the iontophoretically enhanced transport. Results with the HEM experiments generally agreed with model predictions based on the experimental electromobilities. The oligonucleotide HEM ¯ux data also suggest the existence of pores with effective pore radii greater than the effective radii estimated in previous studies with small molecular weight model permeants.