title: Excised porcine cornea integrity evaluation in an in vitro model of iontophoretic ocular research.
abstract: OBJECTIVE
  It is a challenge to adapt traditional in vitro diffusion experiments to ocular tissue. Thus, the aim of this work was to present experimental evidence on the integrity of the porcine cornea, barrier function and maintenance of electrical properties for 6 h of experiment when the tissue is mounted on an inexpensive and easy-to-use in vitro model for ocular iontophoresis.
  
  
  METHODS
  A modified Franz diffusion cell containing two ports for the insertion of the electrodes and a receiving compartment that does not need gassing with carbogen was used in the studies. Corneal electron transmission microscopy images were obtained, and diffusion experiments with fluorescent markers were performed to examine the integrity of the barrier function. The preservation of the negatively charged corneal epithelium was verified by the determination of the electro-osmotic flow of a hydrophilic and non-ionized molecule.
  
  
  RESULTS
  The diffusion cell was able to maintain the temperature, homogenization, porcine epithelial corneal structure integrity, barrier function and electrical characteristics throughout the 6 h of permeation experiment, without requiring CO(2) gassing when the receiving chamber was filled with 25 mM of HEPES buffer solution.
  
  
  CONCLUSIONS
  The system described here is inexpensive, easy to handle and reliable as an in vitro model for iontophoretic ocular delivery studies.
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: T
authors.initials: T
authors.lastname: Gratieri
authors.forename: G M
authors.initials: GM
authors.lastname: Gelfuso
authors.forename: J A
authors.initials: JA
authors.lastname: Thomazini
authors.forename: R F V
authors.initials: RF
authors.lastname: Lopez
mesh_terms: D000818:Animals; D001692:Biological Transport; D003315:Cornea / Q000378:metabolism* / Q000648:ultrastructure; D004553:Electric Conductivity; D004594:Electrophysiology; D019793:Fluorescein / Q000493:pharmacokinetics; D007478:Iontophoresis; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D010539:Permeability; D013499:Surface Properties; D013552:Swine
chemical_list: D019793:Fluorescein