title: Site-specific methylene blue delivery to pilosebaceous structures using highly porous nylon microspheres: an experimental evaluation.
abstract: OBJECTIVE
  This study aimed to evaluate the penetration of methylene blue (MB)-loaded microspheres into pilosebaceous structures of rats.
  
  
  METHODS
  MB was incorporated into 5 microm highly porous nylon microspheres. The microspheres were dispersed into fluid silicone. Male hairless rats were used to evaluate the penetration of MB into hair follicles. After formulation application, MB diffusion was induced and skin biopsies were realized immediately, 2 and 26 hours after MB loaded microspheres application. MB fluorescence was observed with a microscope expanded for fluorescence microscopy.
  
  
  RESULTS
  Position of microspheres and MB diffusion was dependent on delay between microspheres application and harvest. Inside the skin, MB was seen exclusively in the hair follicle and the sebaceous glands. MB diffusion varied from 160+/-50 microm (2 hours after application) to 410+/-70 microm (26 hours after application). MB was also found in the sebaceous glands.
  
  
  CONCLUSIONS
  This study confirms that 5 micro m microspheres are optimally deposited deep within the pilosebaceous structure. In agreement with the literature, when microspheres are topically applied on the skin, they penetrate via a "lipid-rich channel" coating the hair follicles. MB is exclusively distributed in the hair follicles and their accessories.
  
  
  CONCLUSIONS
  This report presents evidence of MB pilosebaceous delivery through the use of microsphere formulation. This is obtained thanks to topical enhancement via the follicular route. This drug delivery system aims to transport MB into the pilosebaceous unit specifically and deeply. Various other applications could derive from this work. For example, such a method might be used to increase the therapeutic index of drugs directed at hair sebaceous gland disorders. Laser treatment of acne or laser hair removal could also benefit of this technique.
authors.affiliation: UPRES EA 2689 INSERM-IFR 114, Pavillon Vancostenobel, Lille University Hospital, 59037 Lille, France. mordon@lille.inserm.fr
authors.forename: Serge
authors.initials: S
authors.lastname: Mordon
authors.forename: Chryslain
authors.initials: C
authors.lastname: Sumian
authors.forename: Jean Marie
authors.initials: JM
authors.lastname: Devoisselle
mesh_terms: D000818:Animals; D016503:Drug Delivery Systems; D018859:Hair Follicle / Q000187:drug effects*; D007202:Indicators and Reagents / Q000008:administration & dosage*; D008297:Male; D008751:Methylene Blue / Q000008:administration & dosage*; D008863:Microspheres; D009757:Nylons; D051381:Rats; D012627:Sebaceous Glands / Q000187:drug effects*
chemical_list: D007202:Indicators and Reagents; D009757:Nylons; D008751:Methylene Blue