Research from the U.K.'s University of Bath could be a downer for companies looking to develop transdermal nanoparticle delivery, hoping to get drugs down to the deepest layers of the skin. According to a paper published in the Journal of Controlled Release, nanoparticles do not cross the skin.
There has been a lot of research on using nanoparticles--particles less than a hundredth of the thickness of a human hair--to deliver drugs across the skin, for cosmetics as well as for pharmaceuticals. However, because the results seem to conflict with each other, the Bath research team decided to look again at the fate of nanoparticles in mammalian skin and found evidence that will perhaps not please groups developing drug delivered across the skin.
The researchers tagged tiny polystyrene beads with florescent markers and used a form of microscopy to track where the beads travelled in the skin. They found that the nanoparticles only entered the stratum disjunctum, the cells that are starting to detach from the skin's surface, in undamaged skin. They didn't travel much farther, just getting into the stratum corneum (the outermost layer of the skin), in skin that was slightly damaged by stripping off the outer layers using adhesive tape (ouch!)
Richard Guy, who led the study, said: "Whereas earlier work has suggested that nanoparticles appear to penetrate the skin, our results indicate that they may in fact have simply been deposited into a deep crease within the skin sample. The skin's role is to act as a barrier to potentially dangerous chemicals and to reduce water loss from the body. Our study shows that it is doing a good job of this."
While this may not be the news that some people want to hear, it may make others feel more comfortable--those who were concerned that nanoparticles that could cause side effects, such as those in sunscreens, won't pass through the skin. Another upside from the work is that researchers may be able to use these findings to design a new type of nanoparticle-based drug formulation that could be applied to the skin and release drug over a long period.
- read the press release
- see the abstract