The study questions whether nanoparticles are able to transport and deliver active ingredients to deeper layers of the skin, after finding that a sample used in tests was not penetrated by “the tiniest of nanoparticles, even when the skin had been partially compromised by stripping the outer layers with adhesive tape.”
The findings may now have implications for cosmetic brands that use nanoparticles in their products for this sole purpose.
According to Professor Richard Guy who led the research, until now previous studies only reached conflicting conclusions as to whether nanoparticles can actually penetrate the skin or not.
“Where 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," he says.
The team of scientists opted for a technique called laser scanning confocal microscopy to examine whether fluorescently-tagged polystyrene beads, ranging in size from 20 to 200 nanometers, were absorbed into the skin.
Guy says that using this particular technology allowed them to “unambiguously visualise and objectively assess what happens to nanoparticles on an uneven skin surface,” and that “while a consumer may draw the conclusion that nanoparticles in their skin creams, are ‘carrying’ an active ingredient deep into the skin, our research ultimately shows this is patently not the case.”
On concluding, the professor says that the study is also a good example of the skin performing its role well, i.e. reducing water loss from the body and acting as a barrier to potentially dangerous chemicals.
The results of the work, published in the Journal of Controlled Release, suggest that it might be possible to design a new type of nanoparticle-based formulation that can be applied to the skin and given a controlled release of the active over a long period of time.
In cosmetics, the two main uses for nanoparticles are as sunblocking agents and for agent delivery. Titanium dioxide and zinc oxide are the main compounds used as blockers.
Structures—such as solid lipid nanoparticles and nanostructured lipid carriers—have been shown to enhance skin hydration and bioavailability of ingredients, improve stability of the encapsulated agent and allow for controlled delivery. Nanocrystals and nanoemulsions are also being investigated
for similar purposes.