Improvement of Keratoprosthesis Biointegration by Covalent Functionalization of PMMA

Abstract

Purpose : Boston keratoprosthesis (KPro) is the most widely used artificial cornea in cases of severe corneal diseases, where a keratoplasty presents a high risk of graft failure. However, the poor adhesion between PMMA and the surrounding corneal tissue may lead to epithelial downgrowth, bacterial infection and possibly to device failure. Although coating of PMMA with different materials such as collagen, RGD domains and hydroxyapatite have been explored, the stability and cost of processing are still the main challenges. Here, we functionalized the PMMA surface with novel and inexpensive hydrophilic moieties to promote cell adhesion and biointegration of the KPro with the host cornea.

Methods : PMMA discs were treated with sodium hydroxide solution to hydrolyze the PMMA surface to the acid functionality (Acid). The carboxylic groups were then treated with (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride/ N-hydroxysuccinimide (EDC/NHS) to form NHS-ester functionalities, that further covalently attached to tris(hydroxymethyl)aminomethane (Tris). Reflection-IR, UV-Vis spectrophotometers and goniometer were used to characterize the functionalized surfaces. Cellular adhesion and cell viability studies using Live/Dead cell and Alamar Blue assays were performed on human corneal epithelial cells (HCEC) and human corneal fibroblast (HCF) seeded on the functionalized surfaces.

Results : Chemical characterization showed the presence of the desired functionalities on the PMMA surface, while the optical properties of the PMMA discs kept intact. The hydrophilicity of treated surface was as follows: Tris > Acid > PMMA. Live/Dead assay revealed that HCEC and HCF cells seeded on the Tris surface has higher cell viability compared to the Acid and PMMA control after 1, 4 and 7 days in culture. Alamar Blue assay showed a similar trend, with the highest cell proliferation rate for Tris, while there were no significant differences between Acid group and PMMA control.

Conclusions : Our results confirm that the covalent functionalization of PMMA with hydrophilic moieties, capable of H-bonding with tissue, enhances the biocompatibility of the surface, promoting cell adhesion and proliferation. Ex vivo studies are in progress to further evaluate the adhesion of the functionalized surface to the native corneal tissue, which will further be extended to in vivo models.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.