Biological surface coating and molting inhibition as mechanisms of TiO2 nanoparticle toxicity in Daphnia magna

The production and use of nanoparticles (NP) has steadily increased within the last decade; however, knowledge about risks of NP to human health and ecosystems is still scarce. Common knowledge concerning NP effects on freshwater organisms is largely limited to standard short-term (≤48 h) toxicity t...

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Bibliographic Details
Published in:PloS one 2011, Vol.6 (5), p.e20112
Main Authors: Dabrunz, André, Duester, Lars, Prasse, Carsten, Seitz, Frank, Rosenfeldt, Ricki, Schilde, Carsten, Schaumann, Gabriele E, Schulz, Ralf
Format: Article
Language:English
Subjects:
Algae
Animals
Aquatic ecosystems
Aquatic organisms
Biocompatibility
Biology
Carbon
Chemistry
Coating
Cytotoxicity
Daphnia - drug effects
Daphnia - metabolism
Daphnia - physiology
Daphnia magna
Daphnia pulex
Disruption
Dose-Response Relationship, Drug
Earth Sciences
Environmental health
Environmental impact
Environmental science
Experiments
Exposure
Fish
Freshwater organisms
Hydrology
Materials Science
Medicine
Molting
Molting - drug effects
Nanomaterials
Nanoparticles
Nanoparticles - chemistry
Nanoparticles - toxicity
Oncorhynchus mykiss
Organisms
Oxidative stress
Particle Size
Photocatalysis
Physiology
Public health
Risk assessment
Studies
Surgical implants
Suspensions
Time Factors
Titanium
Titanium - chemistry
Titanium - metabolism
Titanium - toxicity
Titanium dioxide
Toxicity
Trout
Water - chemistry
Water pollution effects
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Summary:The production and use of nanoparticles (NP) has steadily increased within the last decade; however, knowledge about risks of NP to human health and ecosystems is still scarce. Common knowledge concerning NP effects on freshwater organisms is largely limited to standard short-term (≤48 h) toxicity tests, which lack both NP fate characterization and an understanding of the mechanisms underlying toxicity. Employing slightly longer exposure times (72 to 96 h), we found that suspensions of nanosized (∼100 nm initial mean diameter) titanium dioxide (nTiO(2)) led to toxicity in Daphnia magna at nominal concentrations of 3.8 (72-h EC(50)) and 0.73 mg/L (96-h EC(50)). However, nTiO(2) disappeared quickly from the ISO-medium water phase, resulting in toxicity levels as low as 0.24 mg/L (96-h EC(50)) based on measured concentrations. Moreover, we showed that nTiO(2) (∼100 nm) is significantly more toxic than non-nanosized TiO(2) (∼200 nm) prepared from the same stock suspension. Most importantly, we hypothesized a mechanistic chain of events for nTiO(2) toxicity in D. magna that involves the coating of the organism surface with nTiO(2) combined with a molting disruption. Neonate D. magna (≤6 h) exposed to 2 mg/L nTiO(2) exhibited a "biological surface coating" that disappeared within 36 h, during which the first molting was successfully managed by 100% of the exposed organisms. Continued exposure up to 96 h led to a renewed formation of the surface coating and significantly reduced the molting rate to 10%, resulting in 90% mortality. Because coating of aquatic organisms by manmade NP might be ubiquitous in nature, this form of physical NP toxicity might result in widespread negative impacts on environmental health.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0020112