Presence and associations of retinal pigment epithelium and outer retinal atrophy: the Beijing eye study.

Metallic nanoparticles (MNPs), synthesized from pure metal precursors, have emerged as versatile materials with unique physicochemical and optical properties that underpin their widespread application across diverse scientific and industrial domains []. Structurally, MNPs typically consist of metallic or metal oxide cores, often encapsulated within oxide shells or stabilized by organic and inorganic coatings. Their integration into consumer products, including textiles, packaging, cosmetics, and personal care items, has expanded rapidly, alongside their use in pharmaceuticals, food additives, pigments, semiconductors, sensors, and therapeutic agents [,]. Despite these technological advances, growing evidence highlights the potential adverse biological and environmental consequences of nanomaterials (NMs). Manipulation of matter at the nanoscale has been linked to toxicological outcomes, including oxidative stress, apoptosis, and inflammation, which collectively raise concerns regarding their biosafety []. Embryo–fetal developmental toxicity induced by nanoparticles (NPs) is influenced not only by maternal physiological conditions but also by the physicochemical characteristics of NPs and exposure parameters such as dose and timing []. Zinc oxide nanoparticles (ZnONPs) have been reported to exert detrimental effects across biological systems ranging from plants and microorganisms to vertebrates []. ZnONPs can enter organisms via multiple routes—including inhalation, dermal absorption, ingestion, and parenteral administration—and their ubiquity in the environment further increases human exposure risk []. In vitro studies have demonstrated ZnONP-induced oxidative stress, mitochondrial dysfunction, and disruption of protein and microRNA expression critical for neural development in astrocytes and neuronal cells []. Complementary in vivo investigations confirm neurotoxic outcomes, supporting the hypothesis that ZnONPs accumulate in distinct tissues depending on route and dose of administration [].