In vitro and in vivo assessment of titanium surface modification for coloring the backplate of the Boston keratoprosthesis.

Purpose: Recent use of a titanium (Ti) backplate has improved the design and biocompatibility of the Boston Keratoprosthesis (BKpro). Titanium's shiny metallic appearance, however, makes the cosmetic outcome less favorable. The purpose of this study was to develop and test a coloring surface modification of Ti.
Methods: Ti coloring was achieved using electrochemical anodization. Color assessment included scanning electron microscopy, atomic force microscopy (AFM), x-ray diffraction crystallography (XRD), and Fourier transform infrared spectroscopy (FTIR). Biocompatibility assessment of Ti disks included in vitro proliferation and cytotoxicity in coculture with human corneal limbal epithelial (HCLE) cells, primary human corneal fibroblasts, and immortalized human corneal endothelial cells (HCEnCs), and in vivo intralamellar implantation in rabbit corneas. Histologic appearance (hematoxylin-eosin and trichrome staining) and presence of cell inflammation (CD45), apoptosis (TUNEL), and corneal neovascularization (CD31) were evaluated 27 and 53 days post implantation.
Results: Blue and brown coloration of Ti was achieved. Analysis showed the presence of a nanoporous oxide surface with no chemical change of the modified Ti surface. In vitro assessment showed no significant differences in cell proliferation and cytotoxicity between anodized and nonanodized Ti (P > 0.05; ANOVA for all cell types). Analysis of corneal tissues harboring the Ti disks showed normal cellular appearance, and lack of CD45, TUNEL, and CD31-positive cells.
Conclusions: A biocompatible Ti backplate coloring was achieved by electrochemical anodization. In vitro and in vivo results suggest that the anodized Ti is equally biocompatible and as safe as the standard nonanodized Ti. The color modification of the BKpro may improve the cosmesis and acceptance of the BKpro by patients.