Noninvasive measurement of the 308 nm LED-based UVB protection factor of sunscreens
J. Biophotonics, vol. 14, no. 4, e202000453, doi:10.1002/jbio.202000453 (2021).
Copyright © 2021 The Authors. Journal of Biophotonics published by Wiley-VCH GmbH.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
The current method for determining the sun protection factor (SPF) requires erythema formation. Noninvasive alternatives have recently been suggested by several groups. Our group previously developed a functional sensor based on diffuse reflectance measurements with one UVB LED, which was previously evaluated on pig ear skin. Here we present the results of a systematic in vivo study using 12 sunscreens on 10 volunteers (skin types [ST] I-III). The relationship of the UVB-LED reflectance of unprotected skin and melanin index was determined for each ST. The spatial variation of the reflectance signal of different positions was analyzed and seems to be mainly influenced by sample inhomogeneity except for high-protection factors (PFs) where signal levels are close to detection noise. Despite the low-signal levels, a correlation of the measured LED-based UVB PF with SPF reference values from test institutes with R2 = 0.57 is obtained, suggesting a strong relationship of SPF and LED-based UVB-PF. Measured PFs tend to be lower for increasing skin pigmentation. The sensor design seems to be suitable for investigations where a fast measurement of relative changes of PFs, such as due to inhomogeneous application, bathing and sweating, is of interest.
1 Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Dermatology, Venerology and Allergology, Berlin, Germany
2 Courage + Khazaka electronic GmbH, Cologne, Germany
3 University of Potsdam, Physical Chemistry - innoFSPEC, Potsdam-Golm, Germany
4 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany
5 Hans Karrer GmbH, Augsburg, Germany
6 Beiersdorf AG, Research and Development, Hamburg, Germany
diffuse reflectance spectroscopy, in vivo measurement, nonerythema testing, sun protection factor, sunscreen, UVB-LED