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Silvia Odorcic, Christopher Noel, Debbie Mitra, David Priest, Sabrina Taylor, May Griffith, Rejean Munger, W. Bruce Jackson; Excimer Ablation of Collagen-Based Corneal Substitutes. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4683. doi: https://doi.org/.
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Biosynthetic corneal hydrogels have already undergone successful implantation in human patients with keratoconus and may one day serve as useful alternatives to human donor tissue for surgical and refractive procedures. For synthetic materials to be biocompatible, they should undergo laser ablation in a consistent and reproducible manner. The purpose of our study was 1) to determine the feasibility and consistency of excimer ablation of collagen-based corneal biomimics (hydrogels), 2) to compare the ablation rates of hydrogels with different mechanical properties.
Twelve samples of four different hydrogel formulations (10% recombinant porcine collagen) underwent identical excimer ablations (125 µm PTK, 6.0 mm). All hydrogels were cross-linked using a carbodiimide (EDC), epoxy-based cross-linker (BDDGE) or combination (hybrid) to enhance their mechanical properties. Hydrogel ablations were captured using a specialized high resolution camera (optical profilometer). Custom software was used to extract ablation rates by analyzing silhouette images of hydrogels undergoing ablation.
All hydrogels were amenable to excimer ablation. Ablation rate was plotted against total ablation time for all samples. Hydrogels cross-linked with EDC exhibited extremely consistent ablation rates with minimal inter-sample variability during all time points relative to total ablation time. Hybrid hydrogels (EDC+BDDGE) exhibited moderate ablation consistency between samples, while those cross-linked with BDDGE alone displayed the poorest consistency in ablation rates. The ablation rate of hybrid hydrogels was almost twice as fast as that of EDC cross-linked samples. Hybrid hydrogels also had the most optimized mechanical properties (highest tensile strength and elasticity).
Cross-linked biosynthetic hydrogels can undergo excimer ablation and therefore fulfill one important requirement of synthetic corneal substitutes: biocompatibility. By tailoring the hydrogel’s mechanical properties through cross-linking, ablation rates can also be manipulated. Our hybrid hydrogels have the highest tensile strength and elasticity, as well as the fastest ablation rates of all samples tested. Such properties contribute to enhanced suturability and post-implantation healing. In the future, corneal hydrogels may supplement human donor corneas with tissue-engineered alternatives.
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