Dissolution of nanoparticles (NPs) determines the fate and subsequently the actual exposure of biota to the NPs. Whether and to what extent NPs dissolve or remain in their particulate form in... Show moreDissolution of nanoparticles (NPs) determines the fate and subsequently the actual exposure of biota to the NPs. Whether and to what extent NPs dissolve or remain in their particulate form in aqueous media is thus of pivotal knowledge for the safety assessments of NPs. In this research, secondary data on dissolution of NPs were systematically collected. A range of dissolution rates could be recalculated, as dependent on the characteristics of the NPs and the exposure medium. For example, two nanoparticles which are identical in terms of chemical composition of the particle core and of the coating, had a fully different dissolution behaviour, as subject to different surface modifications. A model was derived for calculating dissolution rate constants of NPs. The model is based on the initial kinetics of dissolution of NPs under different exposure scenarios and on the assumption of pseudo-first order reaction kinetics at the particle surface. Characterizing the dissolution rates and the parameters which modify dissolution allows for grouping of those NPs that dissolve either very slowly or very quickly. This information can be used for risk assessment of NPs, and once sufficient kinetic dissolution data are available, will ultimately allow for development of predictive models for the dissolution kinetics of newly developed nanomaterials. Show less
Fragmentation of plastic waste in the environment can lead to the formation of nanoscale plastic debris (NPD) of size < 1 μm. Although it is reported that NPD can be taken up by organisms, the... Show moreFragmentation of plastic waste in the environment can lead to the formation of nanoscale plastic debris (NPD) of size < 1 μm. Although it is reported that NPD can be taken up by organisms, the current lack of knowledge regarding its toxicokinetics is a problem. It is currently unknown whether/how NPD passes through physiological barriers, and subsequently is biodistributed, biotransformed and/or excreted from organisms. New methods and techniques are being developed at a rapid pace that facilitates gaining insights into the uptake and toxicokinetics of NPD even in complex biotic samples. However, the required knowledge is generated slowly, which hinders environmental risk assessment. In this perspective, we outline the current understanding of the toxicokinetics of NPD in organisms by transferring the acquired knowledge on the toxicokinetics of engineered polymeric NMs to NPD. We briefly discuss the absorption, distribution, metabolism (e.g., biotransformation), and excretion (ADME) of NPD and highlight the knowledge gaps and research required to address them. Building on this, a perspective on toxicokinetics modeling of NPD using physiologically based pharmacokinetic (PBPK) models is presented, discussing the factors that might influence the modeling data and providing recommendations on the factors that need to be considered for developing PBPK models for NPD. Show less
Transformation of nutrients to their nano-form, such as selenium (Se) engineered nanonutrients (Se-ENNs), is expected to enhance the absorption of the nutrients into fish and increase the... Show moreTransformation of nutrients to their nano-form, such as selenium (Se) engineered nanonutrients (Se-ENNs), is expected to enhance the absorption of the nutrients into fish and increase the efficiency of the feed. However, dissolution, aggregation, and release of ENNs from the feed matrix may decrease the efficiency of the Se-ENNs. In this study, we provided fish feed supplemented with Se-ENNs which do not aggregate or dissolve and the particles are also not released from the feed matrix. As a proof of principle, we compared the toxicity of a diet containing Se-ENNs of two different sizes (60 nm and 120 nm) with diets containing ionic Se. The adverse effects were measured by monitoring the survival rate, acetylcholinesterase (AChE) levels and swimming behavior of zebrafish over 21 days of feeding with either the Se-ENNs or ionic Se supplemented fish diets. The number size distribution of the 60 nm Se-ENNs in the diet was similar to that in MilliQ water, while the size distribution of the 120 nm Se-ENNs in the diet was slightly wider. Ion and particle release from Se-ENNs containing diets in the exposure media was not observed, indicating the stability of the particles in the feed matrices. To determine toxicity, zebrafish (Danio rerio) were nourished using a control diet (without Se and Se-ENNs), Se (sodium selenite) containing diets (with 2.4 or 240 mg Se per kg feed) and Se-ENNs containing diets (with 2.4 or 240 mg Se-ENNs of 60 or 120 nm per kg feed) for 21 days. Both sizes of Se-ENNs were taken up in the fish, however only the 120 nm Se-ENNs were detected in the brains of fish. Zebrafish fed with Se-ENNs supplemented diets (60 and 120 nm) showed normal swimming behavior compared to the control. No significant alteration was determined in the AChE activity of the fish fed with the Se-ENNs supplemented diet. In contrast, feeding the zebrafish with a diet containing 240 mg kg−1 Se led to lethal effects. These observations clearly depict the potential benefits of using Se-ENNs as nutrients in fish feed. Show less
Praetorius, A.; Badetti, E.; Brunelli, A.; Clavier, A.; Gallego-Urrea, J.A.G.; Gondikas, A.; ... ; Kammer, F. von der 2020
Heteroaggregation of engineered nanoparticles (ENPs) with suspended particulate matter (SPM) ubiquitous in natural waters often dominates the transport behaviour and overall fate of ENPs in aquatic... Show moreHeteroaggregation of engineered nanoparticles (ENPs) with suspended particulate matter (SPM) ubiquitous in natural waters often dominates the transport behaviour and overall fate of ENPs in aquatic environments. In order to provide meaningful exposure predictions and support risk assessment for ENPs, environmental fate and transport models require quantitative information about this process, typically in the form of the so-called attachment efficiency for heteroaggregation alpha(hetero). The inherent complexity of heteroaggregation-encompassing at least two different particle populations, various aggregation pathways and several possible attachment efficiencies (alpha values)-makes its theoretical and experimental determination challenging. In this frontier review we assess the current state of knowledge on heteroaggregation of ENPs with a focus on natural surface waters. A theoretical analysis presents relevant equations, outlines the possible aggregation pathways and highlights different types of alpha. In a second part, experimental approaches to study heteroaggregation and derive alpha values are reviewed and three possible strategies are identified: i) monitoring changes in size, ii) monitoring number or mass distribution and iii) studying indirect effects, such as sedimentation. It becomes apparent that the complexity of heteroaggregation creates various challenges and no single best method for its assessment has been developed yet. Nevertheless, many promising strategies have been identified and meaningful data can be derived from carefully designed experiments when accounting for the different concurrent aggregation pathways and clearly stating the type of alpha reported. For future method development a closer connection between experiments and models is encouraged. Show less
The chemical composition and properties of environmental media determine nanomaterial (NM) transport, fate, biouptake, and organism response. To compare and interpret experimental data, it is... Show moreThe chemical composition and properties of environmental media determine nanomaterial (NM) transport, fate, biouptake, and organism response. To compare and interpret experimental data, it is essential that sufficient context be provided for describing the physical and chemical characteristics of the setting in which a nanomaterial may be present. While the nanomaterial environmental, health and safety (NanoEHS) field has begun harmonization to allow data comparison and re-use (e.g. using standardized materials, defining a minimum set of required material characterizations), there is limited guidance for standardizing test media. Since most of the NM properties driving environmental behaviour and toxicity are medium-dependent, harmonization of media is critical. A workshop in March 2016 at Duke University identified five categories of test media: aquatic testing media, soil and sediment testing media, biological testing media, engineered systems testing media and product matrix testing media. For each category of test media, a minimum set of medium characteristics to report in all NM tests is recommended. Definitions and detail level of the recommendations for specific standardized media vary across these media categories. This reflects the variation in the maturity of their use as a test medium and associated measurement techniques, variation in utility and relevance of standardizing medium properties, ability to simplify standardizing reporting requirements, and in the availability of established standard reference media. Adoption of these media harmonization recommendations will facilitate the generation of integrated comparable datasets on NM fate and effects. This will in turn allow testing of the predictive utility of functional assay measurements on NMs in relevant media, support investigation of first principles approaches to understand behavioral mechanisms, and support categorization strategies to guide research, commercial development, and policy. Show less
Meesters, J.A.J.; Peijnenburg, W.J.G.M.; Hendriks, A.J.; Meent, D. van de; Quik, J.T.K. 2019
Major molecular mechanisms that underpin the toxicity of nanoparticles (NPs) are the formation of reactive oxygen species and the induction of inflammation. The latter is frequently observed in vitro. Show moreMajor molecular mechanisms that underpin the toxicity of nanoparticles (NPs) are the formation of reactive oxygen species and the induction of inflammation. The latter is frequently observed in vitro and in mammalian organisms, yet in aquatic organisms, such NP-induced inflammatory responses remain largely unexplored. Zebrafish offer a wide range of molecular tools to investigate immune responses in an aquatic organism, and were therefore used here to describe how copper (Cu) NPs (25 nm; 1 mg L−1) and soluble Cu as well as polystyrene (PS) NPs (25 nm; 10 mg L1−) induce innate immune responses, focussing on the skin cells and the intestine as likely organs of interaction. mRNA expression of the immune responsive genes interleukin 1 beta (il1β) and immunoresponsive gene 1-like (irg1l) of CuNP exposed embryos was observed to be weaker in the intestinal tissue compared to the rest of the body, indicating a strong outer epithelium response. Specifically, NPs were observed to accumulate in the cavities of lateral neuromasts in the skin, which coincided with an increased local expression of il1β. Exposure to CuNPs triggered the strongest transcriptional changes in pro-inflammatory-related genes and was also observed to increase migration of neutrophils in the tail, indicating a NP-specific inflammatory response. This is the first in vivo evidence for waterborne NP exposure triggering alterations of immune system regulating genes in the skin and intestine of zebrafish embryos. The observed molecular responses have the potential to be linked to adverse effects at higher levels of biological organization and hence might be used for screening purposes in nanotoxicology or as building blocks for adverse outcome pathways. Show less
The article by Andrea Fabre et al. (Environ. Sci.: Nano, 2017, 4, 670–678) was published with an incorrect title (‘Modeling thesize distribution in a fluidized bed of nanopowder’). The correct... Show moreThe article by Andrea Fabre et al. (Environ. Sci.: Nano, 2017, 4, 670–678) was published with an incorrect title (‘Modeling thesize distribution in a fluidized bed of nanopowder’). The correct article title is ‘Entrainment of nanosized clusters from a nanopowder fluidized bed’. Show less
