title: Infrared spectroscopic imaging tracks lateral distribution in human stratum corneum.
abstract: OBJECTIVE
  To demonstrate the efficacy of infrared (IR) spectroscopic imaging for evaluation of lateral diffusion in stratum corneum (SC) and for elucidation of intermolecular interactions between exogenous agents and SC constituents.
  
  
  METHODS
  In separate experiments, acyl chain perdeuterated oleic acid (OA-d) and deuterated dimethyl sulfoxide (DMSO-d) were applied to the surface of isolated human SC. The lateral distribution of permeant concentrations was monitored using the time-dependence of IR images. Diffusion coefficients (D) were estimated from Fick's second law. Interactions between the exogenous agents and the SC were tracked from changes in CD2 and Amide I stretching frequencies.
  
  
  RESULTS
  Networked glyphs served as the major pathway for lateral distribution of OA-d. In glyph-poor regions, D values from 0.3-1 × 10(-8) cm(2)/s bracketed the OA-d data and apparently decreased with time. Although diffusion of DMSO-d is relatively fast compared to our experimental measurement time, the results suggest values of ~10(-7) cm(2)/s. OA-d spectral changes suggest penetration into the ordered lipids of the SC; DMSO-d penetration results in perturbation of SC keratin structure.
  
  
  CONCLUSIONS
  IR imaging provides concentration profiles, diffusion coefficients, and unique molecular level information about structural changes in the endogenous SC constituents and exogenous agents upon their mutual interaction. Transport along glyphs is the dominant mode of distribution for OA-d.
authors.affiliation: Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey, 07102, USA.
authors.forename: Qihong
authors.initials: Q
authors.lastname: Zhang
authors.forename: Peter
authors.initials: P
authors.lastname: Saad
authors.forename: Guangru
authors.initials: G
authors.lastname: Mao
authors.forename: Russel M
authors.initials: RM
authors.lastname: Walters
authors.forename: Mary Catherine
authors.initials: MC
authors.lastname: Mack Correa
authors.forename: Richard
authors.initials: R
authors.lastname: Mendelsohn
authors.forename: Carol R
authors.initials: CR
authors.lastname: Flach
mesh_terms: D001692:Biological Transport; D003903:Deuterium; D004058:Diffusion; D004121:Dimethyl Sulfoxide / Q000493:pharmacokinetics; D004817:Epidermis / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D019301:Oleic Acid / Q000493:pharmacokinetics; D012869:Skin Absorption; D013055:Spectrophotometry, Infrared; D014018:Tissue Distribution
chemical_list: D019301:Oleic Acid; D003903:Deuterium; D004121:Dimethyl Sulfoxide