Differential bioaccumulation and histopathological changes induced by iron oxide nanoparticles and ferric chloride in the neotropical snail Biomphalaria glabrata

Iron oxide nanoparticles (IONPs) are prominent in nanomedicine, cosmetics, and environmental applications. However, their increasing production, use, and release into the environment raises concerns about their potential risks to aquatic life and human health. This study aimed to evaluate the bioaccumulation, as concentration of small, medium and large iron aggregates in the digestive tubules, histopathological changes, and inflammatory responses in the freshwater snail Biomphalaria glabrata following chronic exposure to gluconic-acid functionalized IONPs (GLA-IONPs) compared to their dissolved counterpart (FeCl₃). The snails were exposed to both iron forms (1.0, 2.5, 6.25, and 15.62 mg L⁻¹) for 28 days. The qualitative and quantitative histopathological assessment of digestive glands was conducted, followed by an analysis of histopathological indices. Both forms of iron accumulated in the digestive gland and induced inflammatory responses, vacuolization, necrosis of secretory cells, and atrophy of the digestive tubules. While FeCl₃ showed greater accumulation in the digestive tubules compared to GLA-IONPs (small: 1.92 to 6.55-fold; medium: 5.84 to 4.6-fold; large aggregates: 26.5 to 8.3-fold), the IONPs caused more severe histopathological changes, including increased atrophy of digestive tubules (1.0 mg L⁻¹: 1.94 -fold) and hemocyte infiltration (1.0 mg L⁻¹: 1.41-fold; 15.62 mg L⁻¹: 1.33-fold). Thus, this study indicates differential bioaccumulation between GLA-IONPs and dissolved Fe, with GLA-IONPs inducing more pronounced toxicity and histopathological damage in the digestive gland of B. glabrata, leading to a loss of digestive functions and confirming their potential risk to aquatic biodiversity.