Nanoparticles--an efficient carrier for drug delivery into the hair follicles.

The penetration and storage behavior of dye-containing nanoparticles (diameter 320 nm) into the hair follicles was investigated. The results were compared to the findings obtained with the same amount of dye in the non-particle form. In the first part of the experiments, the penetration of the dye into the hair follicles was investigated in vitro on porcine skin, which is an appropriate model for human tissue. It was found that the nanoparticles penetrate much deeper into the hair follicles than the dye in the non-particle form, if a massage had been applied. Without massage, similar results were obtained for both formulations. Subsequently, the storage behavior of both formulations in the hair follicles was analyzed in vivo on human skin by differential stripping. Using the same application protocol, the nanoparticles were stored in the hair follicles up to 10 days, while the non-particle form could be detected only up to 4 days. Taking into consideration the surface structure of the hair follicles, it was assumed that the movement of the hairs may act as a pumping mechanism pushing the nanoparticles deep into the hair follicles.