Biotransformation modulates the penetration of metallic nanomaterials across an artificial blood-brain barrier model.

Understanding the potential of nanomaterials (NMs) to cross the blood-brain barrier (BBB), as a function of their physicochemical properties and subsequent behavior, fate, and adverse effect beyond that point, is vital for evaluating the neurological effects arising from their unintentional entry into the brain, which is yet to be fully explored. This is not only due to the complex nature of the brain but also the existing analytical limitations for characterization and quantification of NMs in the complex brain environment. By using a fit-for-purpose analytical workflow and an in vitro BBB model, we show that the physiochemical properties of metallic NMs influence their biotransformation in biological matrices, which in turn modulates the transport form, efficiency, amounts, and pathways of NMs through the BBB and, consequently, their neurotoxicity. The data presented here will support in silico modeling and prediction of the neurotoxicity of NMs and facilitate the tailored design of safe NMs.

Submicron Plastic Adsorption by Peat, Accumulation in Sphagnum Mosses and Influence on Bacterial Communities in Peatland Ecosystems.

The smallest fraction of plastic pollution, submicron plastics (SMPs <1 µm) are expected to be ubiquitous in the environment. No information is available about SMPs in peatlands, which have a key role in sequestering carbon in terrestrial ecosystems. It is unknown how these plastic particles might behave and interact with (micro)organisms in these ecosystems. Here, we show that the chemical composition of polystyrene (PS) and poly(vinyl chloride) (PVC)-SMPs influenced their adsorption to peat. Consequently, this influenced the accumualtion of SMPs by Sphagnum moss and the composition and diversity of the microbial communities in peatland. Natural organic matter (NOM), which adsorbs from the surrounding water to the surface of SMPs, decreased the adsorption of the particles to peat and their accumulation by Sphagnum moss. However, the presence of NOM on SMPs significantly altered the bacterial community structure compared to SMPs without NOM. Our findings show that peatland ecosystems can potentially adsorb plastic particles. This can not only impact mosses themselves but also change the local microbial communities.

The stochastic association of nanoparticles with algae at the cellular level: Effects of NOM, particle size and particle shape.

Association of nanoparticles (NPs) with algae likely plays a critical role in their transfer in aquatic food chains. Although our understanding of the ecotoxicity and fate of NPs in the environment is increasing, it is still unclear how the physicochemical properties of NPs influence their interaction with algae at cellular levels and how this is reflected at a population level. This is due to the limitation in the existing analytical techniques to quantify the association of NPs with cells. To fill this data gap, we applied the novel technique of single-cell inductively coupled plasma mass spectrometry to quantify the cellular association of gold (Au)-NPs with algal cells (Pseudokirchneriella subcapitata) as a function of particle size, shape (spherical 10 nm, spherical 60 nm, spherical 100 nm, rod-shaped 10 × 40 nm, and rod-shaped 50 × 100 nm), and surface chemistry [citrate and natural organic matter (NOM) coating] on a cell-by-cell basis. The association of Au-NPs with algal cells was found to be a random probability following a so-called stochastic process; after 72 h of exposure, less than 45% of the cell population accumulated NPs on their surface. The number of Au-NPs per cell was found to be heterogeneously distributed as some cells were associated with a significantly higher number (e.g. up to 600 spherical 10 nm particles per cell) of Au-NPs than other cells present in the medium. The presence of NOM on the surface of the particles decreased the percentage of cells containing NPs except for the spherical 60 nm Au-NPs. We conclude that some algae within a population can accumulate NPs on their surface and this accumulation is influenced by the size, shape, and surface chemistry of NPs. It is important to understand how NPs may enter aquatic food chains to assess the possible risk.

Method for Extraction and Quantification of Metal-Based Nanoparticles in Biological Media: Number-Based Biodistribution and Bioconcentration.

A multistep sample preparation method was developed to separate metal-based engineered nanoparticles (ENPs) from biological samples. The method was developed using spiked zebrafish tissues and standard titanium dioxide (TiO2) and cerium dioxide (CeO2) ENPs. Single-particle inductively coupled plasma mass spectrometry was used to quantify the separated particles in terms of number concentration. This method demonstrated mass recoveries of more than 90% and did not strikingly alter the median particles size. High number recoveries were calculated for CeO2 ENPs (>84%). Particle number recoveries were poor for TiO2 ENPs (<25%), which could be due to the interference of 48Ca with the measured isotope 48Ti. The method was verified using zebrafish exposed to CeO2 ENPs to test its applicability for nanotoxicokinetic investigations. Total mass of Ce and particle number concentration of CeO2 ENPs were measured in different tissues. Notably, the mass-based biodistribution of Ce in the tissues did not follow the number-based biodistribution of CeO2. Moreover, the calculated mass-based bioconcentration factors showed a different pattern in comparison to the number-based bioconcentration factors. Our findings suggest that considering mass as the sole dose-metric may not provide sufficient information to investigate toxicity and toxicokinetics of ENPs.

The effect of size and sex on PCB and PAH concentrations in crab Portunus pelagicus.

Polychlorinated biphenyl and polycyclic aromatic hydrocarbon concentrations in the hepatopancreas of blue swimming crab (Portunus pelagicus) from the north Persian Gulf were measured. In addition, the relationships between crab size (carapace width) and polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbon (PAH) levels in hepatopancreas were investigated by linear regression analysis. Among the PCBs, congeners 110 and 153 were the most frequent and abundant. The results showed that, except in a few cases, significant relationships between PCB and PAH levels and crab size were positive. Comparison between male and female indicated that the average PCB16, 44, 153, and acenaphthylene, acenaphthene, and anthracene concentrations in hepatopancreas of male crab were found to be significantly higher than those found in the female crab.

Analytical methods for quantifying PS and PVC Nanoplastic attachment to activated sludge Bacteria and their impact on community structure.

Nanoplastics are anticipated to be ubiquitous in various environmental compartments. However, challenges in analytical methods hinder our understanding of risks related to specific nanplastics characteristics such as size and chemical compositions, and interactions between nanoplastics and microorganisms. In this study, we applied fit-for-purpose analytical methods and techniques to understand how nanoplastic chemical composition influences their interaction with bacteria collected from activated sludge. When exposed to polystyrene (PS) and polyvinyl chloride (PVC) nanoplastics for 5 days, the nanoplastics attached to the bacteria. Specifically, on day 1, there was a significant predominance of PS nanoplastics over PVC ones of similar size and shape, possibly due to differences in their chemical composition. After 5 days, there is a substantial decrease in nanoplastics attached to bacteria, suggesting bacterial defence mechanisms may reduce particles attachment over time. The overall bacterial community structure demonstrated a high degree of resilience. This resilience highlights the ability of microbial communities to maintain their structure despite nanoplastic stressors, as evidenced by consistent alpha diversity, PCoA, and PERMANOVA results. Understanding these mechanisms is crucial for assessing nanoplastic fate and thus environmental impacts.

Heavy metal concentration in sediment, benthic, benthopelagic, and pelagic fish species from Musa Estuary (Persian Gulf).

The concentration of Cd, Co, Cu, Ni, and Pb was measured in sediment and three fish species collected from Musa Estuary, Persian Gulf. The concentration order of heavy metals in sediment were Ni > Co > Cu > Pb > Cd >. Concentrations of the heavy metals in the fish were apparently different among the three species. The concentrations of Cd and Ni in fish were Johnius belangerii > Euryglossa orientalis > Liza abu, while the Co and Cu levels were L. abu > E. orientalis > J. belangerii and E. orientalis > L. abu > J. belangerii, respectively. Result of regression analysis showed that there were no significant relationships between metal concentration in fish tissues and sediment, except for Ni concentration in the J. belangerii liver. The concentrations of studied metals in fish muscle were below the permissible limits proposed by FAO, WHO, and EC.

The relationship between heavy metal (Cd, Co, Cu, Ni and Pb) levels and the size of benthic, benthopelagic and pelagic fish species, Persian Gulf.

The concentration of heavy metals was determined in tissues of sole (Euryglossa orientalis), mullet (Liza abu) and croacker fish (Johnius belangerii) from Musa estuary. Generally, the highest concentration of the studied metals in the three species was found in the liver tissue. The levels of Cd and Cu in fish liver were J. belangerii = E. orientalis > L. abu and E. orientalis > L. abu > J. belangerii respectively. The concentrations of Cd and Cu in fish gills were E. orientalis > L. abu = J. belangerii and E. orientalis > L. abu > J. belangerii, respectively, and the level of Cu in muscle was E. orientalis > L. abu = J. belangerii. The results of linear regression analysis indicated that highly significant (p < 0.001) negative relationships were found between fish size and Cd concentrations in the liver of L. abu and Pb in the gills of J. belangerii.

Bioaccumulation of CuO nanomaterials in rainbow trout: Influence of exposure route and particle shape.

The bioaccumulation potential of spherical and rod-shaped CuO nanomaterials (NMs) was assessed in rainbow trout (Oncorhynchus mykiss) exposed via water and diet following the OECD Test Guideline No. 305. Fish were exposed via diet to both NMs at concentrations of 70 and 500 mg Cu/kg for 15 days, followed by 44 days of depuration. For water-borne exposure, only the rod-shaped CuO NMs were tested at 0.08 and 0.8 mg Cu/L for 28 days, followed by 14 days of depuration. The concentration of Cu was determined in fish whole body to derive biomagnification and bioconcentration factors (BMF and BCF). Different tissues were sampled to investigate the total Cu biodistribution and target organs as well as the particle number-based bioaccumulation of CuO NMs. Estimated BMF and BCF values were below the thresholds of concern. However, shape and route influenced depuration. Following dietary exposure, there was a higher depuration of Cu from fish exposed to the rod-shaped compared to the spherical CuO NMs. A higher depuration was also observed for rod-shaped CuO NMs following the dietary exposure compared the aqueous one. Despite the much higher dietary exposure concentrations of rod-shape CuO NMs, similar Cu body burdens were reached via water. Cu was found in particulate form in different tissues. Although these NMs had a low bioaccumulation potential, differences in distribution and elimination patterns of Cu were observed depending on the exposure route and particle shape. Careful consideration of the most relevant exposure route is needed when designing a bioaccumulation experiment for testing NMs.

Exposure protocol for ecotoxicity testing of microplastics and nanoplastics.

Despite the increasing concern about the harmful effects of micro- and nanoplastics (MNPs), there are no harmonized guidelines or protocols yet available for MNP ecotoxicity testing. Current ecotoxicity studies often use commercial spherical particles as models for MNPs, but in nature, MNPs occur in variable shapes, sizes and chemical compositions. Moreover, protocols developed for chemicals that dissolve or form stable dispersions are currently used for assessing the ecotoxicity of MNPs. Plastic particles, however, do not dissolve and also show dynamic behavior in the exposure medium, depending on, for example, MNP physicochemical properties and the medium's conditions such as pH and ionic strength. Here we describe an exposure protocol that considers the particle-specific properties of MNPs and their dynamic behavior in exposure systems. Procedure 1 describes the top-down production of more realistic MNPs as representative of MNPs in nature and particle characterization (e.g., using thermal extraction desorption-gas chromatography/mass spectrometry). Then, we describe exposure system development for short- and long-term toxicity tests for soil (Procedure 2) and aquatic (Procedure 3) organisms. Procedures 2 and 3 explain how to modify existing ecotoxicity guidelines for chemicals to target testing MNPs in selected exposure systems. We show some examples that were used to develop the protocol to test, for example, MNP toxicity in marine rotifers, freshwater mussels, daphnids and earthworms. The present protocol takes between 24 h and 2 months, depending on the test of interest and can be applied by students, academics, environmental risk assessors and industries.

Distribution of metals in the tissues of benthic, Euryglossa orientalis and Cynoglossus arel., and bentho-pelagic, Johnius belangerii., fish from three estuaries, Persian Gulf.

Concentrations of Cd, Co, Cu, Ni, Pb, Fe and Zn were determined in the muscle, liver and gills of three commercial benthic and pelagic fish species (Johnius belangerii, Euryglossa orientalis and Cynoglossus arel) from three estuaries in the northwest Persian Gulf. Metals levels varied significantly depending on the tissues, species and locations. Generally, the results showed that liver accumulate higher concentrations of the metals in comparison to muscle and gills, except in few cases. Among the species, E. orientalis showed the highest levels of Co, Cu, Ni and Fe, while the highest concentrations of Pb and Zn were observed in C. arel. J. belangerii accumulated the highest level of Pb element.

An analytical workflow for dynamic characterization and quantification of metal-bearing nanomaterials in biological matrices.

To assess the safety of engineered nanomaterials (ENMs) and to evaluate and improve ENMs' targeting ability for medical application, it is necessary to analyze the fate of these materials in biological media. This protocol presents a workflow that allows researchers to determine, characterize and quantify metal-bearing ENMs (M-ENMs) in biological tissues and cells and quantify their dynamic behavior at trace-level concentrations. Sample preparation methods to enable analysis of M-ENMs in a single cell, a cell layer, tissue, organ and physiological media (e.g., blood, gut content, hemolymph) of different (micro)organisms, e.g., bacteria, animals and plants are presented. The samples are then evaluated using fit-for-purpose analytical techniques e.g., single-cell inductively coupled plasma mass spectrometry, single-particle inductively coupled plasma mass spectrometry and synchrotron X-ray absorption fine structure, providing a protocol that allows comprehensive characterization and quantification of M-ENMs in biological matrices. Unlike previous methods, the protocol uses no fluorescent dyes or radiolabels to trace M-ENMs in biota and enables analysis of most M-ENMs at cellular, tissue and organism levels. The protocols can be applied by a wide variety of users depending on the intended purpose of the application, e.g., to correlate toxicity with a specific particle form, or to understand the absorption, distribution and excretion of M-ENMs. The results facilitate an understanding of the biological fate of M-ENMs and their dynamic behavior in biota. Performing the protocol may take 7-30 d, depending on which combination of methods is applied.

The joint adverse effects of aged nanoscale plastic debris and their co-occurring benzo[α]pyrene in freshwater mussel (Anodonta anatina).

Although the presence of small-scale plastics, including nanoscale plastic debris (NPD, size <1 µm), is expected in the environment, our understanding of their potential uptake and biodistribution in organisms is still limited. This mostly is because of the limitations in analytical techniques to characterize NPD in organisms' bodies. Moreover, it is still debatable whether aged NPD can sorb and transfer chemicals into organisms. Here, we apply iron oxide-doped polystyrene nanoparticles (Fe-PS NPs) of 270 nm size to quantify the uptake and biodistribution of NPD in freshwater mussels (Anodonta anatina). The Fe-PS NPs were, first, oxidized using heat-activated potassium persulfate treatments to produce NPD (aged particles). Then, the sorption of benzo[a]pyrene (B[α]P), as a model of organic chemicals, into the aged NPD was studied. Chemical oxidation (i.e. aging) significantly decreased the sorption of B[α]P into the particles over 5 days when compared to pristine particles. After 72-h of exposure, A. anatina accumulated NPD in the gills and digestive gland. When exposed to the mixture of NPD and B[α]P, the number of particles in the gills and digestive gland increased significantly compared to the mussels exposed to NPD alone. Moreover, the mixture of NPD and B[α]P increased the activity of Superoxide dismutase and Catalase enzymes in the exposed mussels when compared to the control and to the NPD alone. The present study provides evidence that aged NPD not only could accumulate and alter the toxicity profile of organic chemicals in aquatic organisms, but the chemicals also could facilitate the uptake of NPD (combined effects).

Method for extraction of nanoscale plastic debris from soil.

Sample preparation for extraction of nanoscale plastic debris (NPD, size < 1 µm) from environmental samples is a critical step to prepare NPD for further identification and quantification. Developing a NPD extraction method from soil matrices is particularly challenging due to the complexity of solid matrices. In the present study, we built upon the lessons learned from method development for extraction of microplastics and nanomaterials from environmental samples to develop a sample preparation method for extraction of NPD from soil matrices. The evaluation criteria for the extraction method are size distribution, particle number recovery, and particle mass recovery. Since there is no validated method available to trace and quantify the mass of NPD in complex matrices, we applied polystyrene particles doped with europium (Eu-PS NPs). Standard LUFA soil and field soil were spiked and mixed for 24 h with 1 mg of Eu-PS NPs and the particles were extracted from the matrices of the soils. The extraction method did not significantly influence the size distribution of the particles and the extraction agents did not degrade the Eu-PS NPs. Mass balance calculation suggested recoveries of 82 and 77% of the added Eu-PS NPs in LUFA soil and field soil, respectively. The number recoveries of the particles were 81 and 85% for LUFA soil and field soil, respectively. This method can be further optimized and used as the first building block to develop a generic sample preparation method for the extraction of NPD from soil samples. By combining this developed and verified extraction method with identification and quantification techniques, a fit-for-purpose workflow can be developed to quantify and subsequently understand the fate of NPD in soil.

Parental and trophic transfer of nanoscale plastic debris in an assembled aquatic food chain as a function of particle size.

The existing limitations in analytical techniques for characterization and quantification of nanoscale plastic debris (NPD) in organisms hinder understanding of the parental and trophic transfer of NPD in organisms. Herein, we used iron oxide-doped polystyrene (PS) NPD (Fe-PS-NPD) of 270 nm and Europium (Eu)-doped PS-NPD (Eu-PS-NPD) of 640 nm to circumvent these limitations and to evaluate the influence of particle size on the trophic transfer of NPD along an algae-daphnids food chain and on the reproduction of daphnids fed with NPD-exposed algae. We used Fe and Eu as proxies for the Fe-PS-NPD and Eu-Ps-NPD, respectively. The algae cells (Pseudokirchinella subcapitata) were exposed to 4.8 × 1010 particles/L of Fe-PS-NPD or Eu-PS-NPD for 72 h. A high percentage (>60%) of the NPD was associated with algal cells. Only a small fraction (<11%) of the NPD, however, was transferred to daphnids fed for 21 days on the NPD-exposed algae. The uptake and trophic transfer of the 270 nm Fe-PS-NPD were higher than those for the 640 nm Eu-PS-NPD, indicating that smaller NPD are more likely to transfer along food chains. After exposure to Fe-PS-NPD, the time to first brood was prolonged and the number of neonates per adult significantly decreased compared to the control without any exposure and compared to daphnids exposed to the Eu-Ps-NPD. The offspring of daphnids exposed to Eu-PS-NPD through algae, showed a traceable concentration of Eu, suggesting that NPD are transferred from parents to offspring. We conclude that NPD can be transferred in food chains and caused reproductive toxicity as a function of NPD size. Studies with prolonged exposure and weathered NPD are endeavored to increase environmental realism of the impacts determined.

An environmental ecocorona influences the formation and evolution of the biological corona on the surface of single-walled carbon nanotubes.

Nanomaterials (NMs) taken up from the environment carry a complex ecocorona consisting of dissolved organic matter. An ecocorona is assumed to influence the interactions between NMs and endogenous biomolecules and consequently affects the formation of a biological corona (biocorona) and the biological fate of the NMs. This study shows that biomolecules in fish plasma attach immediately (within <5 min) to the surface of SWCNTs and the evolution of the biocorona is a size dependent phenomenon. Quantitative proteomics data revealed that the nanotube size also influences the plasma protein composition on the surface of SWCNTs. The presence of a pre-attached ecocorona on the surface of SWCNTs eliminated the influence of nanotube size on the formation and evolution of the biocorona. Over time, endogenous biomolecules from the plasma partially replaced the pre-attached ecocorona as measured using a fluorescently labelled ecocorona. The presence of an ecocorona offers a unique surface composition to each nanotube. This suggests that understanding the biological fate of NMs taken up from the environment by organisms to support the environmental risk assessment of NMs is a challenging task because each NM may have a unique surface composition in the body of an organism.

Removal of chromate ions from leachate-contaminated groundwater samples of Khan Chandpur, India, using chitin modified iron-enriched hydroxyapatite nanocomposite.

Chromite ore processing residues (COPR) are real environmental threats, leading to CrO42-, i.e., Cr (VI) leaching into groundwater. It is of serious concern as Cr (VI) is proven to be carcinogenic. Here we emphasize the application of novel and eco-friendly chitin functionalized iron-enriched hydroxyapatite nanocomposite (HAP-Fe0-Ct) in the remediation of Cr (VI)-contaminated groundwater samples collected from Khan Chandpur, India, where the level of Cr (VI) is found to be 11.7 mg/L in a complex aqueous matrix having 793 mg/L of total dissolved solids. Chitin functionality in the composite has resulted in positive zeta potential at circum-neutral pH, favoring electrostatic attraction of chromate ions and resulting in its bulk surface transport. The HAP-Fe0-Ct showed faster kinetics of removal with efficiency (qm = 13.9 ± 0.46 mg/g) for Cr (VI). The composite has shown sorption equilibrium and 100% removal of Cr (VI) within 3 h of interaction time in groundwater samples. No Cr (VI) leaching in the acid wash process at pH 3.5 also suggests chromium's strong chemisorption onto nanocomposite. During the interaction in aqueous solutions, the reduced iron (Fe0) on the nanocomposite becomes oxidized, suggesting the probable simultaneous reduction of Cr (VI) and its co-precipitation. Continuous column extraction of chromate ions was also efficient in both spiked solutions (39.7 ± 0.04 mg/g) and COPR contaminated water (13.2 ± 0.09 mg/g). Reusability up to three cycles with almost complete Cr (VI) removal may be attributed to surface protonation, new binding sites generation, and electron transfer from Fe0 core through defects. The study concludes that HAP-Fe0-Ct could be utilized for continuous Cr (VI) removal from COPR contaminated complex groundwater matrices.

Particle number-based trophic transfer of gold nanomaterials in an aquatic food chain.

Analytical limitations considerably hinder our understanding of the impacts of the physicochemical properties of nanomaterials (NMs) on their biological fate in organisms. Here, using a fit-for-purpose analytical workflow, including dosing and emerging analytical techniques, NMs present in organisms are characterized and quantified across an aquatic food chain. The size and shape of gold (Au)-NMs are shown to control the number of Au-NMs attached to algae that were exposed to an equal initial concentration of 2.9 × 1011 particles mL-1. The Au-NMs undergo size/shape-dependent dissolution and agglomeration in the gut of the daphnids, which determines the size distribution of the NMs accumulated in fish. The biodistribution of NMs in fish tissues (intestine, liver, gills, and brain) also depends on NM size and shape, although the highest particle numbers per unit of mass are almost always present in the fish brain. The findings emphasize the importance of physicochemical properties of metallic NMs in their biotransformations and tropic transfers.

Metal sorption onto nanoscale plastic debris and trojan horse effects in Daphnia magna: Role of dissolved organic matter.

There is a debate on whether the Trojan horse principle is occurring for nanoscale plastic debris (NPD < 1 µm). It is realized that NPD have a high capacity to sorb environmental contaminants such as metals from the surrounding environment compared to their microplastic counterparts, which influences the sorbed contaminants' uptake. Herein, we studied the influence of dissolved organic matter (DOM) on the time-resolved sorption of ionic silver (Ag+) onto polymeric nanomaterials, as models of NPD, as a function of particle size (300 and 600 nm) and chemical composition [polystyrene (PS) and polyethylene (PE)]. Subsequently, the toxicity of NPD and their co-occurring (adsorbed and absorbed) Ag+ on Daphnia magna was determined. Silver nitrate was mixed with 1.2 × 105 NPD particles/mL for 6 days. The extent of Ag+ sorption onto NPD after 6 days was as follows: 600 nm PS-NPD > 300 nm PS-NPD > 300 nm PE-NPD. The presence of DOM in the system increased the sorption of Ag+ onto 300 nm PS-NPD and PE-NPD, whereas DOM decreased the sorption onto 600 nm PS-NPD. Exposure to 1 mg/L NPD or 1 µg/L Ag+ was not toxic to daphnids. However, the mixture of these concentrations of PS-NPD and Ag+ induced toxicity for both sizes (300 and 600 nm). The addition of DOM (1, 10 and 50 mg/L) to the system inhibited the combined toxicity of Ag+ and NPD regardless of the size and chemical composition. Taken together, in natural conditions where the concentration of DOM is high e.g. in freshwater ecosystems, the sorption of metals onto NPD depends on the size and chemical composition of the NPD. Nevertheless, under realistic field conditions where the concentration of DOM is high, the uptake of contaminants in D. magna that is influenced by the Trojan horse principles could be negligible.