title: Effect of the synthetic NC-1059 peptide on diffusion of riboflavin across an intact corneal epithelium.
abstract: OBJECTIVE
  To investigate the effect of the peptide NC-1059 on riboflavin (RF) diffusion across an intact corneal epithelium into the stroma.
  
  
  METHODS
  NC-1059 peptide was synthesized by solid-phase synthesis with 9-fluorenylmethoxycarbonyl chemistry, characterized by reversed-phase HPLC, and matrix-assisted laser desorption ionization time-of-flight mass spectroscopy. The diffusion of RF across embryonic day 18 chick corneal epithelium ex vivo was monitored using confocal microscopy. The depth distributions of RF in the corneal stroma were calculated using a group of linear equations based on the relationship between RF fluorescence intensity and concentration.
  
  
  RESULTS
  Data presented in this study demonstrate that the NC-1059 peptide can transiently open the intact epithelial barrier to allow the permeation of RF into the stroma. The effect of NC-1059 peptide on RF diffusion across the corneal epithelium was concentration and time dependent. The amount of RF reaching a 50-μm depth of chick corneal stoma increased dramatically after exposure to NC-1059 for 10 minutes, reaching a plateau by 30 minutes. The concentrations of RF in the presence of NC-1059 at corneal stromal depths of 50, 100, and 150 μm were significantly higher than in the absence of the peptide, and almost as high as in corneas in which the epithelium first had been physically removed. In addition, a cell viability assay indicated that the NC-1059 peptide did not kill corneal epithelial cells.
  
  
  CONCLUSIONS
  NC-1059 peptide significantly enhances the diffusion of RF across intact corneal epithelium into the stroma.
authors.affiliation: Division of Biology, Kansas State University, Manhattan, KS 66506-4901, USA. ytz@ksu.edu
authors.forename: Yuntao
authors.initials: Y
authors.lastname: Zhang
authors.forename: Pinakin
authors.initials: P
authors.lastname: Sukthankar
authors.forename: John M
authors.initials: JM
authors.lastname: Tomich
authors.forename: Gary W
authors.initials: GW
authors.lastname: Conrad
mesh_terms: D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects; D002642:Chick Embryo; D002851:Chromatography, High Pressure Liquid; D003319:Corneal Stroma / Q000196:embryology / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019573:Epithelium, Corneal / Q000196:embryology* / Q000378:metabolism; D005486:Flavin Mononucleotide / Q000493:pharmacokinetics*; D007473:Ion Channels / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D017136:Ion Transport / Q000187:drug effects; D018613:Microscopy, Confocal; D023421:Models, Animal; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013997:Time Factors
chemical_list: D007473:Ion Channels; C487308:NC-1059; D005486:Flavin Mononucleotide