title: A simple, cross-linked collagen tissue substitute for corneal implantation.
abstract: OBJECTIVE
  To develop a simple corneal substitute from cross-linked collagen.
  
  
  METHODS
  Porcine type I collagen (10%; pH 5), was mixed with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The final homogenous solution was molded to corneal dimensions, cured, and then implanted into rabbits and minipigs by lamellar keratoplasty. The implants were followed for up to 6 months after surgery. Clinical examinations of the cornea included detailed slit lamp biomicroscopy, in vivo confocal microscopy, topography and esthesiometry for nerve function. Histopathologic examinations were also performed on rabbit corneas harvested after 6 months.
  
  
  RESULTS
  Cross-linked collagen (refractive index, 1.35) had optical clarity superior to human corneas. Implanted into rabbit and porcine corneas, only 1 of 24 of the surgical corneas showed a slight haze at 6 months after surgery. All other implants showed no adverse reactions and remained optically clear. Topography showed a smooth surface and a profile similar to that of the contralateral nonsurgical eye. The implanted matrices promoted regeneration of corneal cells, tear film, and nerves. Touch sensitivity was restored, indicating some restoration of function. The corneas with implants showed no significant loss of thickness and demonstrated stable host-graft integration.
  
  
  CONCLUSIONS
  Collagen can be adequately stabilized, using water soluble carbodiimides as protein cross-linking reagents, in the fabrication of corneal matrix substitutes for implantation. The simple cross-linking methodology would allow for easy fabrication of matrices for transplantation in centers where there is a shortage of corneas, or where there is need for temporary patches to repair perforations in emergency situations.
authors.affiliation: National Research Council Canada, Ottawa, Ontario, Canada.
authors.forename: Yuwen
authors.initials: Y
authors.lastname: Liu
authors.forename: Lisha
authors.initials: L
authors.lastname: Gan
authors.forename: David J
authors.initials: DJ
authors.lastname: Carlsson
authors.forename: Per
authors.initials: P
authors.lastname: Fagerholm
authors.forename: Neil
authors.initials: N
authors.lastname: Lagali
authors.forename: Mitchell A
authors.initials: MA
authors.lastname: Watsky
authors.forename: Rejean
authors.initials: R
authors.lastname: Munger
authors.forename: William G
authors.initials: WG
authors.lastname: Hodge
authors.forename: David
authors.initials: D
authors.lastname: Priest
authors.forename: May
authors.initials: M
authors.lastname: Griffith
mesh_terms: D000818:Animals; D001187:Artificial Organs; D001672:Biocompatible Materials / Q000737:chemistry / Q000378:metabolism / Q000627:therapeutic use*; D024042:Collagen Type I / Q000737:chemistry / Q000378:metabolism / Q000627:therapeutic use*; D003315:Cornea / Q000294:innervation / Q000601:surgery*; D016039:Corneal Transplantation / Q000379:methods*; D003432:Cross-Linking Reagents / Q000737:chemistry / Q000378:metabolism; D005022:Ethyldimethylaminopropyl Carbodiimide / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D018613:Microscopy, Confocal; D009416:Nerve Regeneration / Q000502:physiology; D009882:Ophthalmic Nerve / Q000502:physiology; D010539:Permeability; D019919:Prosthesis Implantation; D011817:Rabbits; D013388:Succinimides / Q000737:chemistry; D013552:Swine; D013556:Swine, Miniature
chemical_list: D001672:Biocompatible Materials; D024042:Collagen Type I; D003432:Cross-Linking Reagents; D013388:Succinimides; C001426:N-hydroxysuccinimide; D005022:Ethyldimethylaminopropyl Carbodiimide