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Toxicity of oxidatively degraded quantum dots to developing zebrafish (Danio rerio).

ABSTRACT: Once released into the environment, engineered nanoparticles (eNPs) are subjected to processes that may alter their physical or chemical properties, potentially altering their toxicity vis-à-vis the as-synthesized materials. We examined the toxicity to zebrafish ( Danio rerio ) embryos of CdSecore/ZnSshell quantum dots (QDs) before and after exposure to an in vitro chemical model designed to simulate oxidative weathering in soil environments based on a reductant-driven Fenton's reaction. Exposure to these oxidative conditions resulted in severe degradation of the QDs: the Zn shell eroded, Cd(2+) and selenium were released, and amorphous Se-containing aggregates were formed. Products of QD weathering exhibited higher potency than did as-synthesized QDs. Morphological endpoints of toxicity included pericardial, ocular and yolk sac edema, nondepleted yolk, spinal curvature, tail malformations, and craniofacial malformations. To better understand the selenium-like toxicity observed in QD exposures, we examined the toxicity of selenite, selenate, and amorphous selenium nanoparticles (SeNPs). Selenite exposures resulted in high mortality to embryos/larvae while selenate and SeNPs were nontoxic. Co-exposures to SeNPs + CdCl2 resulted in dramatic increase in mortality and recapitulated the morphological endpoints of toxicity observed with exposure to products of QD weathering. Cadmium body burden was increased in larvae exposed to weathered QDs or SeNP + CdCl2 suggesting the increased potency of products of QD weathering was due to selenium modulation of cadmium toxicity. Our findings highlight the need to examine the toxicity of eNPs after they have undergone environmental weathering processes.

SUBMITTER: Wiecinski PN

PROVIDER: S-EPMC3952569 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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Toxicity of oxidatively degraded quantum dots to developing zebrafish (Danio rerio).

Wiecinski Paige N PN Metz Kevin M KM King Heiden Tisha C TC Louis Kacie M KM Mangham Andrew N AN Hamers Robert J RJ Heideman Warren W Peterson Richard E RE Pedersen Joel A JA

Environmental science & technology 20130802 16

Once released into the environment, engineered nanoparticles (eNPs) are subjected to processes that may alter their physical or chemical properties, potentially altering their toxicity vis-à-vis the as-synthesized materials. We examined the toxicity to zebrafish ( Danio rerio ) embryos of CdSecore/ZnSshell quantum dots (QDs) before and after exposure to an in vitro chemical model designed to simulate oxidative weathering in soil environments based on a reductant-driven Fenton's reaction. Exposur ...[more]

PMID: 23815598

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Project description:Glutathione (GSH), the most abundant vertebrate endogenous redox buffer, plays key roles in organogenesis and embryonic development, however, organ-specific GSH utilization during development remains understudied. Monochlorobimane (MCB), a dye conjugated with GSH by glutathione-s-transferase (GST) to form a fluorescent adduct, was used to visualize organ-specific GSH utilization in live developing zebrafish (Danio rerio) embryos. Embryos were incubated in 20 μM MCB for 1 h and imaged on an epifluorescence microscope. GSH conjugation with MCB was high during early organogenesis, decreasing as embryos aged. The heart had fluorescence 21-fold above autofluorescence at 24 hpf, dropping to 8.5-fold by 48 hpf; this increased again by 72 hpf to 23.5-fold, and stayed high till 96 hpf (18-fold). The brain had lower fluorescence (10-fold) at 24 and 48 hpf, steadily increasing to 30-fold by 96 hpf. The sensitivity and specificity of MCB staining was then tested with known GSH modulators. A 10-min treatment at 48 hpf with 750 μM tert-butylhydroperoxide, caused organ-specific reductions in staining, with the heart losing 30% fluorescence, and, the brain ventricle losing 47% fluorescence. A 24 h treatment from 24-48 hpf with 100 μM of N-Acetylcysteine (NAC) resulted in significantly increased fluorescence, with the brain ventricle and heart showing 312% and 240% increases respectively, these were abolished upon co-treatment with 5 μM BSO, an inhibitor of the enzyme that utilizes NAC to synthesize GSH. A 60 min 100 μM treatment with ethacrynic acid, a specific GST inhibitor, caused 30% reduction in fluorescence across all measured structures. MCB staining was then applied to test for GSH disruptions caused by the toxicants perfluorooctanesulfonic acid and mono-(2-ethyl-hexyl)phthalate; MCB fluorescence responded in a dose, structure and age-dependent manner. MCB staining is a robust, sensitive method to detect spatiotemporal changes in GSH utilization, and, can be applied to identify sensitive target tissues of toxicants.

Dataset Information

Toxicity of oxidatively degraded quantum dots to developing zebrafish (Danio rerio).

Publications

Toxicity of oxidatively degraded quantum dots to developing zebrafish (Danio rerio).

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