title: Penetration of topically applied nanocarriers into the hair follicles of dog and rat dorsal skin and porcine ear skin.
abstract: BACKGROUND
  In humans, topically applied nanocarriers penetrate effectively into the hair follicles where they can be exploited for the localized and targeted treatment of skin disorders.
  
  
  OBJECTIVE
  The objective of the present study was to examine the applicability of particle-based systems for follicular drug delivery in companion animals and livestock, which have a large follicular reservoir.
  
  
  METHODS
  Skin samples from 10 beagle dogs, 14 Wistar rats and four ears from freshly slaughtered cross-bred pigs were used.
  
  
  METHODS
  Fluoresceinamine labelled poly (L-lactide-co-glycolide) nanocarriers (256 or 430 nm) were applied on the different skin samples. After penetration, skin biopsies were removed and cryohistological cross sections prepared and investigated with regard to the follicular penetration depths (in μm ± standard deviation) of the nanocarriers using confocal laser scanning microscopy.
  
  
  RESULTS
  In canine, rat and porcine hair follicles, the smaller nanoparticles were detected at mean follicular penetration depths of 630.16 ± 135.75 μm, 253.55 ± 47.36 μm and 653.40 ± 94.71 μm, respectively. The larger particles were observed at average follicular depths of 604.79 ± 132.42 μm; 262.87 ± 55.25 μm and 786.81 ± 121.73 μm, respectively, in canine, rat and porcine hair follicles. Statistically significant differences (P < 0.05) in the mean follicular penetration depths of the differently sized nanocarriers could be determined for the canine and porcine skin samples.
  
  
  CONCLUSIONS
  The mean follicular penetration depths of the differently sized nanocarriers were mostly significantly different between the different species, which might be due to different species-specific follicular dimensions. This issue needs to be addressed specifically in further studies.
authors.affiliation: Center of Experimental and Applied Cutaneous Physiology (CCP), Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany.
authors.forename: Fanny
authors.initials: F
authors.lastname: Knorr
authors.affiliation: Center of Experimental and Applied Cutaneous Physiology (CCP), Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany.
authors.forename: Alexa
authors.initials: A
authors.lastname: Patzelt
authors.affiliation: Center of Experimental and Applied Cutaneous Physiology (CCP), Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany.
authors.forename: Maxim E
authors.initials: ME
authors.lastname: Darvin
authors.affiliation: Department of Biopharmaceutics and Pharmaceutical Technology, Saarland University, University Campus, 66123, Saarbrücken, Germany.
authors.forename: Claus-Michael
authors.initials: CM
authors.lastname: Lehr
authors.affiliation: Department of Biopharmaceutics and Pharmaceutical Technology, Saarland University, University Campus, 66123, Saarbrücken, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schäfer
authors.affiliation: Department of Veterinary Medicine, Institute of Veterinary Pathology, Freie Universität Berlin, Robert-von-Ostertag-Strasse 15, 14163, Berlin, Germany.
authors.forename: Achim D
authors.initials: AD
authors.lastname: Gruber
authors.affiliation: Department of Veterinary Medicine, Institute of Veterinary Pathology, Freie Universität Berlin, Robert-von-Ostertag-Strasse 15, 14163, Berlin, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Ostrowski
authors.affiliation: Center of Experimental and Applied Cutaneous Physiology (CCP), Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Lademann
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D001672:Biocompatible Materials; D004285:Dogs; D016503:Drug Delivery Systems; D004423:Ear; D005456:Fluorescent Dyes; D018859:Hair Follicle / Q000378:metabolism*; D053758:Nanoparticles / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012869:Skin Absorption / Q000187:drug effects*; D013552:Swine
chemical_list: D001672:Biocompatible Materials; D005456:Fluorescent Dyes