Poster N16 - Development of Cerium Oxide Nanoparticle-based Permanent Nanocatalyst Intraocular Lens for Treatment of Age-related Macular Degeneration

Introduction: Age-related macular degeneration (AMD) is an acquired retinal disease characterized by progressive vision loss due to degenerative changes in the macula, the central part of the retina responsible for critical vision functions, including photoreceptor and retinal pigment epithelial cells (RPEs) degeneration. Since reactive oxygen species (ROS) and chronic inflammation in the retina are believed to be essential contributors to AMD pathogenesis, the regulation of ROS and inflammation levels may be effective therapeutic targets. Cerium oxide nanoparticles (CeNPs) exhibit characteristics similar to enzymes involved in the cellular antioxidant mechanism such as catalase, superoxide dismutase (SOD), and peroxidase. CeNPs possess excellent activity characterized by repeated oxidation state exchanges of metal ions on the nanoparticle surface, unaffected significantly by temperature or ambient conditions. Therefore, CeNPs demonstrate autocatalytic properties, attracting attention for their therapeutic potential in the scavenging of ROS.
In this study, we propose a novel alternative permanent treatment by embedding CeNPs, known for their excellent antioxidant and anti-inflammatory effects, into intraocular lens (IOL). The permanent nanocatalyst IOL exhibited excellent ROS scavenging properties, and high biocompatibility with retinal tissue-derived cells.

Materials and

Methods: Materials: Cerium (III) nitrate hexahydrate, hydrogen peroxide, imidazole, 10-undecenoic acid (10-UA), 2-hydroxyethyl methacrylate (HEMA), 2-phenylethyl acrylate(PEA), min. 92%, PEG-PEA, Styrene, nOA, BDDA, Darocur, SOD Assay Kit – WST, Amplex red Assay Kit, EGDMA, cell counting kit-8 (CCK-8).
Preparation of hydrophobic CeNPs: To synthesize the CeNPs, cerium acetate precursor solution, prepared by dissolving cerium acetate in acetone, and imidazole precursor solution, prepared by dissolving imidazole in acetone and deionized water mixture, and the appropriate amount of 10-UA were mixed with a stirring at 40°C. After 2 days of reaction, the reaction mixture was poured into an excess amount of acetone to precipitate the CeNPs. The precipitated CeNPs were centrifuged, washed three times with acetone, and vacuum-dried.
Fabrication of CeNPs-IOL: CeNPs-IOL was fabricated via free-radical polymerization using UV cross-linking.
1. PEA/HEMA IOL: First, the appropriate concentration of CeNPs were dissolved in nOA. PEA, HEMA, CeNPs-nOA, BDDA, and Darocur were gently mixed and poured into a mold, and the mixture was irradiated with UV light for 2 hrs.
2. PHS IOL: First, the appropriate concentration of CeNPs were dissolved in styrene. PEG-PEA, HEMA, CeNPs-styrene, EGDMA, and Darocur were gently mixed and poured into a mold, and the mixture was irradiated with UV light for 2 hrs.

Results, Conclusions, and Discussions: One drawback of Hydrophilic IOL, a type of IOL for cataract treatment, is their tendency to develop calcification over time, leading to opacity. In contrast, hydrophobic IOL does not develop opacity even after insertion and are increasingly used for cataract treatment and vision correction due to their stable physical and optical properties. Therefore, in this study, we developed a hydrophobic acrylic foldable IOL capable of permanently encapsulating CeNPs without compromising its optical characteristics. Initially, to develop hydrophobic CeNPs that can be well dispersed within the hydrophobic lens without optical degradation, the surface of the nanoparticles was modified using 10-UA with double bond. The uniform, 4nm 10-UA modified CeNPs were confirmed using transmission electron microscopy (TEM). The solubility of CeNPs was tested using the protocols of commercially available approved intraocular lenses, PEA/HEMA IOL and PHS IOL. Furthermore, the optimal concentration of CeNPs that ensures maximum efficiency in scavenging reactive oxygen species (ROS) without compromising transparency and properties, even after acetone washing, was confirmed. Despite being a hydrophobic IOL, the ROS-scavenging efficiency was observed to be remarkably high, reaching approximately 30%.
To evaluate the biocompatibility of CeNP-embedded IOL (CeNP-IOL), CCK-8 cell proliferation/cytotoxicity assay was performed using human RPE cells. Furthermore, the cytoprotective effect of the catalytic IOL was verified by co-culturing cells and CeNP-IOL in an environment with excessive oxidative stress induced using ROS-inducing factors. Subsequently, cell viability was confirmed to assess the scavenging ability of ROS.
Finally, the CeNP-IOL was inserted into the eyes of an ex vivo porcine model of macular degeneration according to the cataract surgery protocol. Subsequently, the cytoprotective effect and inhibition of retinal degenerative changes by the catalytic IOL were assessed using histological analysis.
This study provides a strategy for the development of a highly efficient permanent catalytic IOL capable of treating multiple ophthalmic conditions concurrently. Additionally, it is anticipated to pioneer a novel field of biomaterials adept at controlling oxidative stress in vivo, with potential applications extending to diseases induced by harmful ROS.

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