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


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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    ABSTRACT: Cutaneous permeation is a critical parameter when topical application of sunscreens containing antioxidants is considered. The aim of this study was to evaluate the cutaneous penetration of most marketed UV-filters combined with trans-resveratrol (RES) and beta-carotene (BTC) since few studies report skin penetration when such compounds are applied. Formulations containing octocrylene, octyl methoxycinnamate, avobenzone and bemotrizinole were prepared and supplemented or not with BTC, or with RES, or with both compounds in combination. Penetration studies were performed using Franz vertical diffusion cells and porcine ear skin as the biological membrane. The quantification of UV-filters and antioxidants in the stratum corneum (SC), viable epidermis plus dermis and receptor fluid was performed by HPLC. Results suggested that UV-filters and antioxidants did not permeate the skin but were retained for 12h post application. About 90% and 80%, respectively, of the total penetrated amount of UV-filters and antioxidants was found in the SC. Interestingly, it was observed that BTC, alone or combined with RES, reduced the skin retention of UV-filters on average by 63%. In conclusion, this study demonstrated that the combination of antioxidants and UV-filters in sunscreens is advantageous for cutaneous penetration, since BTC and BTC+RES improved sunscreen safety by reducing delivery of the four UV-filters in the study into SC and viable epidermis. Copyright © 2015. Published by Elsevier B.V.
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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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    ABSTRACT: Emulsions stabilized by solid particles in place of emulsifiers are known as Pickering emulsions. The dense coating made of solid particles adsorbed at the surface of emulsion droplets provides specific properties that strongly influence the transfer of drugs from emulsion droplets to the skin. After a short review about physicochemical properties of Pickering emulsions, the skin delivery of drugs controlled by Pickering emulsions is discussed with the help of examples. Further, possible mechanisms by which such emulsions contribute to drug transport and/or accumulation in the skin are discussed. Penetration-enhancing activity specific to Pickering emulsions comes from the adhesion of droplets onto the skin surface, allowing the transfer of loaded drug molecules to the skin. Application of Pickering emulsions for topical delivery of drugs and cosmetics may be quite a direct implementation of already existing manufacturing processes of classical emulsions.
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