Polylactic Acid (PLA) Particles for Hair Follicle Targeting: Controlled Release of Incorporated Fluorochromes After Skin Contact

  • Antonia Todorova, Clinical Research Center for Hair and Skin Science, Department of Dermatology , Charité-Universitätsmedizin Berlin, Germany
  • Fiorenza Rancan, Clinical Research Center for Hair and Skin Science, Department of Dermatology, Charité-Universitätsmedizin Berlin, Germany
  • Elsa Luciani, Institut de Biologie et Chimie des Protéines, Lyon, France
  • Christina Graf, Physikalische Chemie, Institut für Chemie und Biochemie Freie Universität Berlin, Germany
  • Bernard Verrier, Université Lyon 1, UMR CNRS 5223 ‘IMP’, Laboratoire des Matériaux Polymères et Biomatériaux, Villeurbanne Cedex, France
  • Wolfram Sterry, Clinical Research Center for Hair and Skin Science, Department of Dermatology , Charité-Universitätsmedizin Berlin, Germany
  • Ulrike Blume-Peytavi, Clinical Research Center for Hair and Skin Science, Department of Dermatology , Charité-Universitätsmedizin Berlin, Germany
  • Annika Vogt, Clinical Research Center for Hair and Skin Science, Department of Dermatology, Charité-Universitätsmedizin Berlin, Germany

We recently introduced biodegradable poly-lactic acid (PLA) particles as interesting carriers for hair follicle and sebaceous gland targeting. PLA particles, although stable in aqueous solution, destabilized upon contact with the skin surface and released incorporated dye. The aim of this study was to further investigate the influence of different dye loads on particle stability.
Changes in particle conformation, penetration in hair follicles and dye release of two PLA particles (207nm DiAsp-PLA and 164nm BP-PLA) were investigated after topical application on human skin explants using adhesive tape stripping, fluorescence microscopy, flow cytometry and transmission electron microscopy.
The TEM analysis of particles after contact with skin surface revealed an enhanced stability of DiAsp-PLA particles with respect to BP-PLA NP and was confirmed by the investigation of particle distribution on skin surface through adhesive tape stripping. Accumulation of 207nm DiAsp PLA particles was observed in approximately 60% of hair follicles. Fluorescent dye release started upon skin application and remained constant during observation time . On contrary, upon topical application of 164nm BP-PLA particles a faster dye release and clearance was observed. Fluorescent dye release started upon skin application and persisted up to 8 hours with a maximum at 4 hours. Flow cytometry analysis of epidermal cells revealed a slight shift in mean fluorescence intensity favoring cells of skin incubated with PLA particles compared to controls but particles associated with epidermis cells was not detected.
These results suggest that the release of drugs from PLA particles and their stability upon contact with skin can be controlled by loading particles with excipients having different affinity for skin. The higher stability of 207nm DiAsp-loaded PLA NP particle penetration in hair follicles after a single application suggest that such particles could be ideal carriers for hair follicle targeting and prolonged local dermatotherapy.