Toxicity of silicon dioxide nanoparticles with varying sizes on the cornea and protein corona as a strategy for therapy.

The human cornea is exposed directly to particulate matter (PM) in polluted air. This exposure can cause eye discomfort and corneal injury. Ultrafine PM (diameter <100 nm) is thought to be particularly harmful to health, but there is limited research investigating its toxicity to the eye. In this study, we evaluated toxicity differences among 30-, 40-, 100- and 150-nm silicon dioxide nanoparticles (SiO NPs) on the cornea. A 24-hour in vitro exposure of primary human corneal epithelial cells (hCECs) to ultrafine (30 and 40 nm) SiO NPs produced toxicity, as evidenced by cell membrane damage, reduced cell viability, increased cell death and mitochondrial dysfunction. In vivo exposure to the same nanoparticles produced observable corneal injury. These effects were more severe with ultrafine than with fine (100 and 150 nm) SiO NPs. Common antioxidant compounds, e.g., glutathione, did not protect the cornea from SiO NP-induced damage. However, foetal bovine serum (FBS) did significantly reduce toxicity, likely by forming a protective protein corona around the nanoparticles. This finding suggests that FBS (or its derivatives) may be a useful clinical therapy for corneal toxicity caused by ultrafine particulates.