Transdermal drug delivery system (TDDS) has attracted more and more attention due to its significant potential in avoiding the hepatic first-pass metabolism

maintaining a constant and prolonged drug level

and providing a local target and convenience for administration. However

the stratum corneum

namely the outermost layer of the skin

acts as a biological barrier

which would limit the transdermal delivery of drug molecules

especially the hydrophilic ones. For this reason

the development of effective methods to enhance the penetration of drugs through skin has become important. In recent years

as a kind of drug carrier for TDDS

the nanoparticle has become popular because of its excellent properties such as high entrapment efficiency

reduced enzymatic degradation

controlled release rate and large specific surface area which can easily accumulate on the surface of the skin to promote the penetration of the drug. This article mainly reviews the research progress in polymeric nanoparticles for TDDS

including the mechanism of enhanced penetration

the combination of nanoparticles and active penetration methods for TDDS. With reference to the problems existing in current studies

suggestions are also proposed.