Evaluation of nanoparticle (NP) toxicity in respect to NP physicochemistry and reactivity in the aquatic environment

The increasing application of nanoparticles (NPs) has led to increased occurrence of engineered NPs in the aquatic environment. Understanding the toxicity of NPs in the aquatic environment is dependent on linking NP physicochemistry with toxicological responses and while research has been moving towards this direction, the link has not been fully understood yet. The present study critically reviewed adsorption and desorption processes of organic environmental contaminants on TiO2 NPs and evaluated interactions of NPs with compounds of different physicochemistry already existing in the aquatic environment as contaminants. Aquatic toxicity of the new generation lead-halide perovskite NPs was evaluated relative to lead ion dissolution. Finally, the sedimentation of NP agglomerates during a traditional fish early-life stage toxicity test, a major limitation of assessing NP toxicity in the aqueous phase, was addressed by development of an exposure chamber designed to keep NP agglomerates in homogeneous dispersion. The model organisms used in the present study to evaluate NP toxicity were larvae and adult zebrafish Danio rerio and the unicellular green fresh water alga Chlorella vulgaris. The main findings were: 1) sorption of environmental contaminants on NPs can change the bioavailability of the contaminant in the aqueous phase. Specifically, sorption of copper and benzo(a)pyrene (under fluorescent light) on NPs reduced the adsorbent bioavailability. On the contrary, benzo(a)pyrene and anthracene, when adsorbed on TiO2 or Si NPs, were photo-catalysed under UVA and in the case of benzo(a)pyrene, highly toxic photoby-products showed increased bioavailability in larval zebrafish; 2) lead-halide perovskite acute toxicity was attributed to lead ion dissolution based on induction of metallothionein 2 gene expression through aqueous and dietary exposure, and 3) the perovskite-spiked diets did not disrupt zebrafish gut microbiome after a 14-d exposure while disruption of gut microbiota by equivalent Pb(NO3)2 diets was observed; finally, 4) higher toxicity was found when NPs were tested using an exposure chamber that allowed continuous NP dispersion, indicating toxicity is depended on the dispersion state of NPs. This study has expanded our knowledge on NP surface physicochemistry and interactions with surrounding compounds in the aqueous phase; has confirmed metal ion dissolution out of metallic NPs and linked perovskite NP toxicity to lead ion dissolution as well as linked NP toxicity to NP dispersion in the aqueous phase contributing to a better understanding of NP properties and reactivity relation to toxicity in the aquatic environment

Aqueous Hg²⁺ associates with TiO₂ nanoparticles according to particle size, changes particle agglomeration, and becomes less bioavailable to zebrafish

Altinok, Ilhan/0000-0003-3475-521X; Boyle, David/0000-0001-6919-7137; Patsiou, Danae/0000-0002-4863-3486; Henry, Theodore/0000-0002-9675-9454WOS: 000374604100024PubMed: 26970871Engineered nanoparticles (NPs) have unique physicochemistry and potential to interact with other substances in the aqueous phase. Here, gene [metallothionein 2 (mt2)] expression changes in larval zebrafish were used to evaluate the association between aqueous Hg2+ and TiO2 (NPs and bulk particle size control) to investigate the relationship between changes in Hg2+ behavior and TiO2 size. During 24 h exposures, TiO2 agglomerates increased in size and in the presence of 25 mu g Hg-2+/L, greater increases in size were observed. the concentration of Hg2+ in suspension also decreased in the presence of TiO2-NPs. Mercury increased expression of mt2 in larval zebrafish, but this response was lessened when zebrafish were exposed to Hg2+ in the presence of TiO2-NPs, and which suggests that TiO2-NPs alter the bioavailability of Hg2+ to zebrafish larvae. This ameliorative effect of TiO2 was also likely due to surface binding of Hg2+ because a greater decrease in mt2 expression was observed in the presence of 1 mg/L TiO2-NPs than 1 mg/L TiO2-bulk. in conclusion, the results show that Hg2+ will associate with TiO2-NPs, TiO2-NPs that have associated Hg2+ will settle out of the aqueous phase more rapidly, and agglomerates will deliver associated Hg2+ to sediment surfaces. (C) 2016 Elsevier B.V. All rights reserved

Exposure to Pb-halide perovskite nanoparticles can deliver bioavailable Pb but does not alter endogenous gut microbiota in zebrafish

Lead-halide perovskite nanoparticles (NPs) are a new technology, and investigation of toxicity is of considerable importance due to the potential lead (Pb) release into the environment. The aim of the study was to investigate aqueous and dietary toxicity of Pb-halide perovskite NP and Pb in zebrafish Danio rerio. Perovskite NP toxicity was evaluated in zebrafish by mortality, gene expression, histopathology, and phylogenetic analysis of gut microbiota. Zebrafish larvae were exposed to five Pb-halide perovskite NPs in parallel with Pb(NO3)2 exposures, and zebrafish adults were exposed to the three perovskite NPs that caused the strongest effect and Pb(NO3)2. No median lethal concentration (LC50) was observed for zebrafish larvae exposed to up to 200 mg/L of perovskite NPs for 96 h. Mortality, metallothionein 2 (mt2) and δ-aminolevulinic acid dehydratase (ala-d) gene expression (24-h exposure) in zebrafish larvae after aqueous perovskite NPs exposures did not differ from total Pb concentration - response curves. The lack of differences in mortality and gene expression between perovskite NPs and soluble Pb after aqueous exposure suggest that toxicity from perovskite NPs can be attributed to bioavailable Pb rather than nano-specific effects. Induction of mt2 and reduction of ala-d expression levels in liver tissues showed Pb bioavailability after 2-d and 4-d dietary exposure to perovskite-spiked feeds. Changes in gut microbiota of adult zebrafish were detected after 14-d exposure to Pb-spiked food, but no changes were detected from perovskite-NP spiked food. The phylogenetic analysis identified different microbiome profiles of Pb-fed fish compared to perovskite-fed fish suggesting a different mechanism of toxicity. Exposure to Pb-halide perovskite NPs led to absorption of Pb likely from release of Pb ions rather than absorption of NPs. Pb-halide perovskite NPs can release bioavailable Pb and this needs to be considered during the development of this technology.Accepted versio

Interlaboratory comparison of microplastic extraction methods from marine biota tissues: A harmonization exercise of the Plastic Busters MPAs project

In the framework of the Plastic Busters MPAs project, a harmonization exercise on two methods of microplastic extraction from biological samples i.e. 15% H2O2 digestion and 10% KOH digestion was carried out. The two methods were tested in four laboratories on fish gastrointestinal tracts and mussel tissues spiked with polyethylene, polypropylene and polyethylene terephthalate. The recovery percentage of microplastics for each method, species and polymer tested were overall similar among laboratories, and interlaboratory coefficient of variation was less than 11% for the majority of samples. Microplastic recovery rates for the two methods were similar for each sample tested, but overall mean interlaboratory recovery rate using KOH (96.67%) was higher than H2O2 (88.75%). Results validate the use of both methods for extracting microplastics from biota tissues. However, when comparing the two methods in terms of microplastic recovery rate, time consumed, technical difficulties and cost, digestion with 10% KOH is considered optimal.En prensa2,35