Aggravated Visual Toxicity of Eco-Corona on Micro(Nano)Plastics in Marine Medaka (<i>Oryzias melastigma</i>)

In marine environments, micro(nano)plastics (MNPs) and biomolecules will inevitably combine to form eco-corona. However, the presence of eco-corona may change MNP physicochemical properties, thereby impacting their biological effects. This study investigated how eco-corona influenced the visual toxicity and potential mechanisms of MNPs in marine medaka. The results showed that MNPs, with or without eco-corona, can cause eye malformation, retinal damage, eye cell apoptosis, and suppression of visual-related gene expression. Although MNPs caused visual impairments, they did not lead to abnormal behavior during light-dark alternation. Moreover, while 5 μm polystyrene microplastics (MP5) caused eye swelling, 50 nm polystyrene microplastics (NP50) resulted in more severe retinal damage. Regardless of eco-corona, NP50 induced greater activity during dark periods compared with MP5. Notably, eco-corona exacerbated retinal damage and cell apoptosis caused by MNPs, leading to increased activity. The analysis of visual-related genes revealed that eco-corona aggravated the visual toxicity of MNPs, and NP50 exhibited greater visual toxicity than MP5, regardless of eco-corona. Overall, smaller MNPs may pose higher risks to the visual system in real marine environments. This study provides novel insights into the effects of eco-corona in MNP-induced visual toxicity and highlights the importance of considering biomolecules in marine environments.