P1.15 Standardized protocols allow specific targeting of vellus hair follicles and terminal hair follicles, respectively

A. Vogt, R. Toll, S. Gontschoukow, S. Hadam, J. Lademann, U. Blume-Peytavi

Center of Experimental and Applied Cutaneous Physiology, Department of Dermatology, Charité - University Medicine Berlin, Germany

In intact skin, the stratum corneum considerably impairs interfollicular penetration processes. This tight barrier, however, is interrupted in the infrainfundibular parts of the human hair follicles which may represent not only a reservoir, but also a major entry point for topically applied compounds. Selective follicular targeting allows to direct active compounds at high concentrations into the hair follicles and may lead to new therapeutic approaches in the treatment of hair disorders. Microspheres, loaded with fluorescent dyes for proof of concept studies or with active compounds for therapeutic use, are valuable tools for efficient drug delivery into the hair follicle. The aim of this project was to standardize the application method of microparticles in aqueous and alcoholic solutions ranging from 6 mm to 40 nm in size on fresh human skin samples. Infrared irradiation, massage, tape stripping and cyanoacrylate tape stripping were assessed to optimize follicular penetration. The microspheres were localized by fluorescence microscopy on cryosections.

Depending on size and formulation, microspheres allow to target different sites of the hair follicle, and targeting of different hair follicle types can be achieved by minor modifications of the application protocol.