Research Papers: General

Film thickness frequency distribution of different vehicles determines sunscreen efficacy

[+] Author Affiliations
Myriam Sohn, Georgios Imanidis

University of Applied Sciences and Arts Northwestern Switzerland, School of Life Sciences, Institute of Pharmaceutical Technology, Gründenstrasse 40, 4132 Muttenz/Basel, Switzerland

University of Basel, Department of Pharmaceutical Sciences, Klingelbergstrasse 50, 4056 Basel, Switzerland

Adeline Hêche

University of Basel, Department of Pharmaceutical Sciences, Klingelbergstrasse 50, 4056 Basel, Switzerland

Bernd Herzog

BASF GmbH, Köchlinstrasse 1, 79639 Grenzach-Whylen, Germany

J. Biomed. Opt. 19(11), 115005 (Nov 18, 2014). doi:10.1117/1.JBO.19.11.115005
History: Received July 23, 2014; Revised September 22, 2014; Accepted September 22, 2014
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Abstract.  Sun protection factor (SPF) frequently differs between sunscreens containing the same composition of ultraviolet (UV) filters that primarily define sunscreen efficacy. We tested the hypothesis that the thickness frequency distribution of the sunscreen film is also responsible for and can explain the divergence in the measured SPF. For this, we developed a method to measure film thickness from the difference of topography before and after application of 2mg/cm2 of sunscreen on pig ear epidermal membrane. The influence of five vehicle formulations and of application pressure and spreading time on mean thickness (Smean), Smean to median ratio, and SPF in vitro was investigated. The vehicle had a significant impact, low vehicle viscosity resulting in a smaller Smean, larger Smean to median ratio, and lower SPF in vitro than high viscosity; continuous oil phase produced the largest Smean and SPF values. A long spreading time reduced Smean and SPF and increased application pressure reduced SPF. There was a positive correlation between Smean and SPF in vitro, underlining the relevance of film thickness for interpreting UV protection differences of formulations with the same filter composition. This work demonstrated a strong influence of vehicle and application conditions on sunscreen efficacy arising from differences in film thickness distribution.

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© 2014 Society of Photo-Optical Instrumentation Engineers

Citation

Myriam Sohn ; Adeline Hêche ; Bernd Herzog and Georgios Imanidis
"Film thickness frequency distribution of different vehicles determines sunscreen efficacy", J. Biomed. Opt. 19(11), 115005 (Nov 18, 2014). ; http://dx.doi.org/10.1117/1.JBO.19.11.115005


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