摘要：The mechanism of skin penetration enhancement by ultrasound under sonophoresis (US) or by an electrical field under iontophoresis (IP) was investigated using hairless mouse skin in vitro . The seven model chemicals with different molecular weights (122—1485) were dissolved in a hydrophilic gel. Donor gel with the chemicals was loaded on the skin surface and then the skin was treated with US (300 kHz, 5.2 W/cm2, 5.4% duty-cycle) and IP (0.32±0.03 mA/cm2) individually or with US and IP in combination (US+IP). The penetration profiles of the chemicals with a molecular weight of less than 500 were influenced by the presence of an electric charge, the profiles of ionized chemicals for US+IP were the same as profiles for IP, while the penetration flux of a non-ionized chemical synergistically increased with US+IP compared with the individual flux of US and IP. The chemicals with molecular weight of more than 1000 showed synergistic effects with US+IP. The mathematical simulation assuming a bilayer skin model revealed that the synergistic effects were mainly influenced by electroosmosis in the stratum corneum (SC). Therefore the synergistic effects of US+IP was mainly caused by the SC diffusivity of chemicals increased by US and the electroosmotic water flow by IP application.
