Article

In vitro Percutaneous Absorption and in vivo Stratum Corneum Distribution of an Organic and a Mineral Sunscreen

Centre de Recherche Pierre Fabre, Tolosa de Llenguadoc, Midi-Pyrénées, France
Skin pharmacology and physiology (Impact Factor: 2.37). 02/2007; 20(1):10-20. DOI: 10.1159/000096167
Source: PubMed

ABSTRACT

Sunscreens, whose main function is to protect the skin against the harmful effects of solar irradiation, should remain at the skin surface or impregnate the first layers of the stratum corneum only and not penetrate into the underlying living tissue. The goal of this work was to assess the penetration of titanium dioxide (TiO(2)) and methylene bis-benzotriazoyl tetramethylbutylphenol (MBBT), included in a broad-spectrum sunscreen formulation, into human skin in vivo, using the tape stripping method, and in vitro, using a compartmental approach. An additional objective was to propose an easy and minimally invasive approach to determining the percutaneous uptake of sunscreens following topical application. TiO(2) and MBBT were quantified using colorimetric assay and HPLC analysis, respectively. The transmission electron microscopy and particle-induced X-ray emission techniques were used to localize the TiO(2) in skin sections. More than 90% of both sunscreens was recovered in the first 15 tape strippings. In addition we have shown that the remaining 10% did not penetrate the viable tissue, but was localized in the furrows and in the opened infundibulum. Less than 0.1% of MBBT was detected in the receptor medium, and no TiO(2) was detected in the follicle, viable epidermis or dermis. Thus, this in vivo and in vitro penetration study showed an absence of TiO(2) penetration into the viable skin layers through either transcorneal or transfollicular pathways and negligible transcutaneous absorption of MBBT. However, differences in distribution within the stratum corneum reinforced the need for a complementary approach, using minimally invasive in vivo methodology and in vitro compartmental analysis. This combination represents a well-adapted method for testing the safety of topically applied sunscreen formulations in real-life conditions.

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Available from: Alain Mavon, Sep 10, 2015
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    • "Skin exposure to nano particle-containing sunscreens leads to incorporation of TiO 2 and ZnO in the stratum corneum, which may alter certain properties due to particleparticle , particle-skin, and skin-particle-light physicochemical interactions[195]. Overall, the weight of scientific evidence suggests that insoluble nanoparticles used in sunscreens pose no or negligible risk to human health[196,197,201202203204205206207208209210however there are some discrepancies in the results probably related to differences in techniques and methods, laboratory conditions, and the absence of standardized evaluation protocols. The reason for these results is unclear based on the observation that most other nano particle types (polymers, metals and carbon nano tubes) permeate the skin. "

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    • "However, cutaneous penetration is a critical issue regarding the development of sunscreens containing antioxidants. UV-filters must remain in the stratum corneum to be safe and effective (Mavon et al., 2007; Yang et al., 2008). On the other hand antioxidant compounds should be able to reach viable skin layers to afford satisfactory photoprotection, since UV radiation penetrates deeply into the skin (Saija et al., 2000). "
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    • "The deep skin penetration of solid particles may be considered as an issue regarding possible health concerns of nanoparticles. Such topic has been largely addressed concerning inorganic particles used in sunscreen formulations, titanium dioxide, and zinc oxide (Mavon et al. 2007; Nohynek at al. 2008; Bolzinger et al. 2011). There is a wealth of experimental data showing that such inorganic particles do not penetrate the skin deeply and that their penetration is restricted to the stratum corneum upon reasonable exposure durations (hours to days). "
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