Acoustic mechanisms as an enhancer for transdermal drug delivery

An acoustic enhancer for transdermal drug delivery has been studied for several decades in the field of engineering. However, its delivery mechanisms are not well understood. In this study, simple experiments were proposed to simulate a human skin system with a rat back skin for transdermal insulin delivery. Unfocused 0.5‐, 1‐, and 3‐MHz ultrasound transducers were used for acoustic enhancers, and a heating wire loop was used for a nonacoustic enhancer. Ultrasound worked as a very effective delivery enhancer. The acoustic enhancer even gave better enhancement of insulin transportation than the nonacoustic enhancer, such as the heating wire loop, while almost the same amount of heating from both enhancers was applied to the diffusion cell. These results show that the thermal effect in the acoustic enhancer works as a major mechanism for transdermal insulin delivery. However, the nonthermal effects of ultrasound was also observed to contribute to enhance the transdermal insulin delivery.