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 (TiO2) 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. TiO2 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 TiO2 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 TiO2 was detected in the follicle, viable epidermis or dermis. Thus, this in vivo and in vitro penetration study showed an absence of TiO2 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.

Keywords:
Titanium dioxide, Tinosorb M, Tape stripping, Skin absorption, Electron microscopy, Particle-induced X-ray emission
This content is only available via PDF.
© 2007 S. Karger AG, Basel
2006
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.