title: Hydroxyapatite for keratoprosthesis biointegration.
abstract: OBJECTIVE
  Integration of keratoprosthesis with the surrounding cornea is very important in preventing bacterial invasion, which may cause ocular injury. Here the authors investigated whether hydroxyapatite (HAp) coating can improve keratoprosthesis (KPro) biointegration, using polymethyl methacrylate (PMMA)--the principal component of the Boston KPro--as a model polymer.
  
  
  METHODS
  HAp coatings were induced on PMMA discs after treatment with concentrated NaOH and coating with poly-dopamine (PDA) or polydopamine and then with 11-mercaptoundecanoic acid (11-MUA). Coatings were characterized chemically (Fourier transform infrared spectroscopy [FTIR], energy dispersive X-ray spectroscopy [EDX]) and morphologically (SEM) and were used as substrates for keratocyte growth in vitro. Cylinders of coated PMMA were implanted in porcine corneas ex vivo for 2 weeks, and the force required to pull them out was measured. The inflammatory reaction to coated discs was assessed in the rabbit cornea in vivo.
  
  
  RESULTS
  FTIR of the coatings showed absorption bands characteristic of phosphate groups, and EDX showed that the Ca/P ratios were close to those of HAp. By SEM, each method resulted in morphologically distinct HAp films; the 11-MUA group had the most uniform coating. The hydroxyapatite coatings caused comparable enhancement of keratocyte proliferation compared with unmodified PMMA surfaces. HAp coating significantly increased the force and work required to pull PMMA cylinders out of porcine corneas ex vivo. HAp coating of implants reduced the inflammatory response around the PMMA implants in vivo.
  
  
  CONCLUSIONS
  These results are encouraging for the potential of HAp-coated surfaces for use in keratoprostheses.
authors.affiliation: Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA.
authors.forename: Liqiang
authors.initials: L
authors.lastname: Wang
authors.forename: Kyung Jae
authors.initials: KJ
authors.lastname: Jeong
authors.forename: Homer H
authors.initials: HH
authors.lastname: Chiang
authors.forename: David
authors.initials: D
authors.lastname: Zurakowski
authors.forename: Irmgard
authors.initials: I
authors.lastname: Behlau
authors.forename: James
authors.initials: J
authors.lastname: Chodosh
authors.forename: Claes H
authors.initials: CH
authors.lastname: Dohlman
authors.forename: Robert
authors.initials: R
authors.lastname: Langer
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Kohane
mesh_terms: D000818:Animals; D001187:Artificial Organs; D049109:Cell Proliferation; D002478:Cells, Cultured; D020099:Coated Materials, Biocompatible; D003315:Cornea / Q000737:chemistry*; D060527:Corneal Keratocytes / Q000166:cytology; D017886:Durapatite / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D019904:Polymethyl Methacrylate; D019736:Prostheses and Implants; D011817:Rabbits; D033081:Shear Strength; D013052:Spectrometry, X-Ray Emission; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013552:Swine
chemical_list: D020099:Coated Materials, Biocompatible; D019904:Polymethyl Methacrylate; D017886:Durapatite