title: On-line visualization of dye diffusion in fresh unfixed human skin.
abstract: OBJECTIVE
  The purpose of the current study was to develop a new method to examine the diffusion in fresh unfixed human skin on-line.
  
  
  METHODS
  Full thickness skin samples were cut perpendicular to the skin surface (cutting plane facing upwards) with a new cutting device forming part of the final diffusion cell. The donor solution contained 0.1 mg/ml Bodipy FL C5 (moderately lipophilic) dissolved in citric acid buffer, pH 5.0, and the acceptor phase consisted of phosphate-buffered saline, pH 7.4. Images were taken with confocal laser scanning microscopy (CLSM) every 10 min for 8 h.
  
  
  RESULTS
  This new method enabled for the first time visualization of concentration profiles in different skin layers simultaneously as a function of time. For this model penetrant, Bodipy FL C5 showed that the lower stratum corneum layer constitutes the greatest barrier to diffusion. Furthermore, there is preferred partitioning of this probe in epidermis vs. either stratum corneum or dermis.
  
  
  CONCLUSIONS
  The on-line diffusion cell in combination with CLSM is a promising tool to study diffusion processes of dyes in fresh unfixed skin on-line. The method has the potential to access deeper skin layers as well as to visualize diffusion processes in cells.
authors.affiliation: Leiden/Amsterdam Center for Drug Research, Department of Pharmaceutical Technology, Leiden University, 2300 RA Leiden, The Netherlands.
authors.forename: Ylva Y
authors.initials: YY
authors.lastname: Grams
authors.forename: Lynne
authors.initials: L
authors.lastname: Whitehead
authors.forename: Paul
authors.initials: P
authors.lastname: Cornwell
authors.forename: Joke A
authors.initials: JA
authors.lastname: Bouwstra
mesh_terms: D000465:Algorithms; D002264:Carboxylic Acids; D004396:Coloring Agents / Q000493:pharmacokinetics*; D003199:Computer Systems; D004058:Diffusion; D015194:Diffusion Chambers, Culture; D005456:Fluorescent Dyes; D006801:Humans; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D015233:Models, Statistical; D009862:Online Systems; D012867:Skin / Q000033:anatomy & histology*; D012869:Skin Absorption / Q000502:physiology*
chemical_list: D002264:Carboxylic Acids; D004396:Coloring Agents; D005456:Fluorescent Dyes; C436864:Oregon Green 488 carboxylic acid