Quantitative evaluation of accelerated transdermal drug delivery by electroosmosis via frustoconical porous microneedles†

Electroosmosis-based transdermal drug delivery via frustoconical porous microneedles (F-PMNs) is studied by quantitative fluorescence analysis of the drug models penetrated into excised pig skin. An array of 300 μm height F-PMN made of poly-glycidyl methacrylate is modified by a grafted thin film of anionic poly (2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) or a cationic poly-(3-acrylamidopropyl trimethylammonium) (PAPTAC) to generate electroosmotic flow (EOF) upon application of current through the needles. Owing to the synergy of the EOF-promoted transport and the expansion of the stratum corneum with the frustoconical protrusions, the penetration rates of rhodamine B (479 Da) and FITC-dextran (4 kDa and 10 kDa) are found to be accelerated by more than 10 times. In addition, the F-PMNs modified with PAMPS and PAPTAC show similar delivery rates in opposite directions, enabling the possible dual-mode delivery from both anode and cathode in an integrated iontophoresis device.