title: Differential stripping: determination of the amount of topically applied substances penetrated into the hair follicles.
abstract: The determination of penetration pathways of topically applied substances into the skin is the subject of several investigations. Recently, follicular penetration has become a major focus of interest. To date, a direct, non-invasive quantification of the amount of topically applied substance penetrated into the follicles had not been possible. The development of such a method was the aim of this study. Therefore, the advantages of both stripping techniques, tape stripping and cyanoacrylate skin surface biopsy, were combined and evaluated. Tape stripping was used to remove the part of the stratum corneum that contained the topically applied dye. Subsequently, the follicular contents were ripped off by cyanoacrylate skin surface biopsy. The combined method termed "differential stripping" was evaluated in vitro and in vivo, and the amount of topically applied fluorescent dye penetrated into the hair follicles was quantified after different penetration times. After 30 min, 5% of the recovered concentration of sodium fluorescein was found in the follicular infundibula, where it was still detectable after 48 h. Altogether, the results of this investigation revealed that differential stripping is a new method that can be used to study the penetration of topically applied substances into the follicular infundibula non-invasively and selectively.
authors.affiliation: Center of Experimental and Applied Cutaneous Physiology, Department of Dermatology, Medical Faculty Charité, Berlin, Germany. alexa.teichmann@charite.de
authors.forename: Alexa
authors.initials: A
authors.lastname: Teichmann
authors.forename: Ute
authors.initials: U
authors.lastname: Jacobi
authors.forename: Michael
authors.initials: M
authors.lastname: Ossadnik
authors.forename: Heike
authors.initials: H
authors.lastname: Richter
authors.forename: Stefan
authors.initials: S
authors.lastname: Koch
authors.forename: Wolfram
authors.initials: W
authors.lastname: Sterry
authors.forename: Jürgen
authors.initials: J
authors.lastname: Lademann
mesh_terms: D000287:Administration, Topical; D000328:Adult; D000818:Animals; D001706:Biopsy / Q000379:methods*; D003287:Contrast Media / Q000493:pharmacokinetics; D003487:Cyanoacrylates / Q000493:pharmacokinetics*; D005260:Female; D019793:Fluorescein / Q000493:pharmacokinetics; D018859:Hair Follicle / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D008297:Male; D012869:Skin Absorption; D034421:Sus scrofa
chemical_list: D003287:Contrast Media; D003487:Cyanoacrylates; D019793:Fluorescein