Aqueous toxicity and food chain transfer of quantum dots^™ in freshwater algae and Ceriodaphnia dubia

Abstract

Innovative research and diagnostic techniques for biological testing have advanced during recent years because of the development of semiconductor nanocrystals. Although these commercially available, fluorescent nanocrystals have a protective organic coating, the inner core contains cadmium and selenium. Because these metals have the potential for detrimental environmental effects, concerns have been raised over our lack of understanding about the environmental fate of these products. U.S. Environmental Protection Agency test protocol and fluorescence microscopy were used to determine the fate and effect of quantum dots (QDs; Qdot® 545 ITK™ Carboxyl Quantum Dots [Fisher Scientific, Fisher part Q21391MP; Invitrogen Molecular Probes, Eugene, OR, USA]) using standard aquatic test organisms. No lethality was measured following 48-h exposure of Ceriodaphnia dubia to QD suspensions as high as 110 ppb, but the 96-h median lethal concentration to Pseudokirchneriella subcapitata was measured at 37.1 ppb. Transfer of QDs from dosed algae to C. dubia was verified with fluorescence microscopy. These results indicate that coatings present on nanocrystals provide protection from metal toxicity during laboratory exposures but that the transfer of core metals from intact nanocrystals may occur at levels well above toxic threshold values, indicating the potential exposure of higher trophic levels. Studies regarding the fate and effects of nanoparticles can be incorporated into models for predictive toxicology of these emerging contaminants.

Effects and Implications of Trophic Transfer and Accumulation of CeO2 Nanoparticles in a Marine Mussel

“…This corresponds well with the results of two other studies using marine invertebrates. 14,26 For pseudofeces excreted by the mussels, a pseudofeces-water partitioning coefficient (K p , the ratio of pseudofeces Ce concentration to the concentration of Ce in the surrounding We found accumulation of CeO 2 in mussel tissues over time in all experimental groups, which when considered with the constant Ce concentrations in pseudofeces suggests that some ENMs were being stored either in the digestive gland or elsewhere in the organism and were not immediately captured in pseudofeces and excreted. It is unlikely that a significant amount remained in the gut as bivalves have been shown to excrete micrometer-scale particles after 30 h or less with and without additional food.…”

“…Several studies have looked at the trophic transfer and biomagnification of ENMs in terrestrial, 13 freshwater, 14 and marine 15 food…”

Toxicity, bioaccumulation and biomagnification of silver nanoparticles in green algae (Chlorellasp.), water flea (Moina macrocopa), blood worm (Chironomusspp.) and silver barb (Barbonymus gonionotus)

“…An implication is that AgNPs accumulated by primary producers such as phytoplankton or algae could then be available to the next level of predators in the food chain, which could lead to broader ecological effects. There are several sources of evidence that nano materials can be transferred in the food chain; for example, from protozoa to rotifer (Nowack and Bucheli, 2007) and algae (Pseudokirchneriella subcapitata) to zooplankton (Ceriodaphnia dubia) (Bouldin et al, 2008). D. magna can accumulate nano TiO 2 from the ambient environment with high bioaccumulation factor (BCF) values (1,232.28-118,062.84 L kg -1 ) (Zhu et al, 2010).…”

Interactions between engineered nanomaterials and agricultural crops: implications for food safety

“…Notably, the majority of existing data related to ENM trophic transfer come from studies in freshwater plants and aquatic invertebrates, e.g., transfer of quantum dots from ciliated protozoans to rotifers, nTiO 2 from daphnia to zebrafish and quantum dots from dosed algae to C. dubia (Bouldin et al, 2008;Holbrook et al, 2008;Zhu et al, 2010). No biomagnification was observed in the above aquatic studies, with bioaccumulation factors (BAFs) ranging from 0.004-0.04 (Hou et al, 2013).…”