Study shows quantum dots can penetrate skin through minor abrasions.

Researchers at North Carolina State University have found
that quantum dot nanoparticles can penetrate the skin if there is an abrasion,
providing insight into potential workplace concerns for healthcare workers or
individuals involved in the manufacturing of quantum dots or doing research on
potential biomedical applications of the tiny nanoparticles.



While the study shows that quantum dots of different sizes,
shapes and surface coatings do not penetrate rat skin unless there is an
abrasion, it shows that even minor cuts or scratches could potentially allow
these nanoparticles to penetrate deep into the viable dermal layer, or living
part of the skin, and potentially reach the bloodstream.



Dr. Nancy Monteiro-Riviere, professor of investigative
dermatology and toxicology at NC State's College of Veterinary Medicine, tested
the ability of the quantum dots to penetrate rat skin at 8 and 24 hour
intervals. The experiment evaluated rat skin in various stages of distress,
including healthy skin, skin that had been stripped using adhesive tape and
skin that had been abraded by a rough surface. The researchers also assessed
whether flexing the skin affected the quantum dots' ability to penetrate into
the dermal layer. Monteiro-Riviere co-authored the study with doctoral student
Leshuai Zhang.



While the study indicates that acute, or short term, dermal
exposure to quantum dots does not pose a risk of penetration (unless there is
an abrasion), Monteiro-Riviere notes "there is still uncertainty on long term
exposure." Monteiro-Riviere explains that the nanoparticles may be able to
penetrate skin if there is prolonged, repeated exposure, but so far no studies
have been conducted to date to examine that possibility. Quantum dots are
fluorescent nanoparticles that may be used to improve biomedical imaging, drug
delivery and diagnostic testing.



This finding is of importance to risk assessment for
nanoscale materials because it indicates that skin barrier alterations, such as
wounds, scrapes, or dermatitis conditions, could affect nanoparticle
penetration and that skin is a potential route of exposure and should not be
overlooked.



The study found that the quantum dots did not penetrate even
after flexing the skin and that the nanoparticles only penetrated deep into the
dermal layer when the skin was abraded. Although quantum dots are incredibly
small, they are significantly larger than the fullerenes, or buckyballs, that
Monteiro-Riviere showed in a 2007 study in Nano Letters can deeply and rapidly
penetrate healthy skin when there is repetitive flexing of the skin.



Additionally, Monteiro-Riviere's laboratory previously
showed quantum dots of different size, shape and surface coatings could
penetrate into pig skin. The anatomical complexity of skin and species
differences should be taken into consideration when selecting an animal model
to study nanoparticle absorption/penetration. Human skin studies are also being
conducted, but "it is important to investigate species differences and to
determine an appropriate animal model to study nanoparticle penetration,"
Monteiro-Riviere says. "Not everyone can obtain fresh human skin for
research."



Nanoparticles are generally defined as being smaller than
100 nanometres (thousands of times thinner than a human hair), and are expected
to have widespread uses in medicine, consumer products and industrial
processes.