Comparison of candidate materials for a synthetic osteo-odonto keratoprosthesis device

Purpose. Osteo-odonto keratoprosthesis is one of the most successful forms of keratoprosthesis surgery for end-stage corneal and ocular surface disease. There is a lack of detailed comparison studies on the biocompatibilities of different materials used in keratoprosthesis. The aim of this investigation was to compare synthetic bioinert materials used for keratoprosthesis surgery with hydroxyapatite (HA) as a reference. Methods. Test materials were sintered titanium oxide (TiO₂), aluminum oxide (Al₂O₃), and yttria-stabilized zirconia (YSZ) with density >95%. Bacterial adhesion on the substrates was evaluated using scanning electron microscopy and the spread plate method. Surface properties of the implant discs were scanned using optical microscopy. Human keratocyte attachment and proliferation rates were assessed by cell counting and MTT assay at different time points. Morphologic analysis and immunoblotting were used to evaluate focal adhesion formation, whereas cell adhesion force was measured with a multi-mode atomic force microscope. Results. The authors found that bacterial adhesion on the TiO₂, Al₂O₃, and YSZ surfaces were lower than that on HA substrates. TiO₂ significantly promoted keratocyte proliferation and viability compared with HA, Al₂O₃ and YSZ. Immunoflu-orescent imaging analyses, immunoblotting, and atomic force microscope measurement revealed that TiO₂ surfaces enhanced cell spreading and cell adhesion compared with HA and Al₂O₃. Conclusions. TiO₂ is the most suitable replacement candidate for use as skirt material because it enhanced cell functions and reduced bacterial adhesion. This would, in turn, enhance tissue integration and reduce device failure rates during keratoprosthesis surgery.