Skin Penetration by Quantum Dots

By: Johann W. Wiechers, PhD, JW Solutions

Posted: December 9, 2008

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It is, therefore, interesting to read a later paper on quantum dot penetration from the same group.⁵ Again, they used both the small spherical and the larger ellipsoid quantum dots but only with the anionic coating that—in the previous study—localized mainly in the epidermis by 8 hr (small spherical quantum dots) or did not penetrate until 24 hr (larger ellipsoid quantum dots). The objective of the new study was to investigate whether flexion, tape stripping and abrasion could cause an increase in the penetration of quantum dots of different sizes and shapes.

Using rat skin instead of pig skin (as used in the first study), it was found that on intact skin the skin penetration of both quantum dots was primarily limited to the uppermost stratum corneum layers. Barrier perturbation by tape stripping did not cause penetration, but abrasion with sandpaper allowed the quantum dots to penetrate deeper into the dermal layers. As a result, quantum dot penetration not only depends on nanoparticle size and charge, but also on species differences in the skin and hair follicle density. Occasionally, retention of quantum dots was observed in the hair follicles in abraded skin.

Penetration of nanoparticles not only occurs on the surface of the stratum corneum layers or within the stratum corneum layers; these particles may also penetrate further down the skin with skin flexing.⁵ These findings are in full agreement with the influence of massage as described in this author’s column in the January issue of Cosmetics & Toiletries magazine.

References
1. JP Ryman-Rasmussen, JE Riviere and NA Monteiro-Riviere, Penetration of intact skin by quantum dots with diverse physicochemical properties, Toxicol Sci 91 159–165 (2006)
2. GJ Nohynek, J Lademann, C Ribaud and MS Roberts, Grey goo on the skin? Nanotechnology, cosmetic and sunscreen safety, Crit Rev Toxicol 37 251–277 (2007)
3. FR Bettley, The influence of detergents and surfactants on epidermal permeability, Br J Dermatol 77 98–100 (1965)
4. M Sznitowska, S Janicki and A Baczek, Studies on the effect of pH on the lipoidal route of penetration across stratum corneum, J Control Rel 76 327–335 (2001)
5. LW Zhang and NA Monteiro-Riviere, Assessment of quantum dot penetration into intact, tape-stripped, abraded and flexed rat skin, Skin Pharmacol Physiol 21 166–180