Melanin-Like Nanomedicine Functions as a Novel RPE Ferroptosis Inhibitor to Ameliorate Retinal Degeneration and Visual Impairment in Dry Age-Related Macular Degeneration.

Ferrous ion accumulation and lethal oxidative stress mediate irreversible retinal pigment epithelial (RPE) cell ferroptosis and subsequent photoreceptor degeneration, a potential key pathogenic factor in the onset of dry age-related macular degeneration (dAMD), causing irreversible vision loss in the global elderly population. However, currently, no effective interventional treatment strategy exists in clinical practice. Herein, lesion site-targeted melanin-like nanoparticles, named ConA-MelNPs, are designed as a novel ferroptosis inhibitor for retinal degenerative diseases. ConA-MelNPs possessed chelating iron ion characteristics, alleviating severe mitochondrial damage caused by oxidative stress and protecting RPE cells from ferroptosis induced by sodium iodate (NaIO3). In a preclinical dAMD mouse model, a single intravitreal injection of ConA-MelNPs yielded significant responses in electroretinograms and visually-driven optomotor responses in visually impaired mice, resisting the challenge posed by secondary NaIO3-induced injuries, with the long-term sustainability of its therapeutic effect. Mechanistically, ConA-MelNPs achieve a therapeutic effect by interrupting the detrimental cascade involving "RPE cell ferroptosis, lethal oxidative stress, and microglial proinflammatory activation," affording the restoration of retinal homeostasis. The synthesized ConA-MelNPs demonstrated good biosafety, with no detected ophthalmic or systemic side effects. Collectively, ConA-MelNPs are proposed as a promising therapeutic option for atrophic retinal diseases such as dAMD.