Device-assisted transdermal drug delivery.

Transdermal drug delivery is a prospective drug delivery strategy to complement the limitations of conventional drug delivery systems including oral and injectable methods. This delivery route allows both convenient and painless drug delivery and a sustained release profile with reduced side effects. However, physiological barriers in the skin undermine the delivery efficiency of conventional patches, limiting drug candidates to small-molecules and lipophilic drugs. Recently, transdermal drug delivery technology has advanced from unsophisticated methods simply relying on natural diffusion to drug releasing systems that dynamically respond to external stimuli. Furthermore, physical barriers in the skin have been overcome using microneedles, and controlled delivery by wearable biosensors has been enabled ultimately. In this review, we classify the evolution of advanced drug delivery strategies based on generations and provide a comprehensive overview. Finally, the recent progress in advanced diagnosis and therapy through customized drug delivery systems based on real-time analysis of physiological cues is highlighted.