Nanoparticles in wastewaters: Hazards, fate and remediation

Algal EPS modifies the toxicity potential of the mixture of polystyrene nanoplastics (PSNPs) and triphenyl phosphate in freshwater microalgae Chlorella sp

Triphenyl phosphate (TPP) and polystyrene nanoplastics (PSNPs) are prevalent freshwater contaminants obtained mainly from food packaging, textiles and electronics. Algal extracellular polymeric substances (EPS), a part of natural organic matter, may influence these pollutants' behaviour and toxicity. The presence of EPS can enhance the aggregation of TPP-PSNP mixtures, and reduce the bioavailability, and thus the toxicity potential. Understanding the mutual interactions between TPP, PSNPs, and EPS in the aquatic environment is a prerequisite for the environmental risk assessment of these chemicals. The study examines the toxicity effects of various surface-modified PSNPs (1 mg/L of plain, animated, and carboxylated) and TPP (0.05, 0.5, and 5 mg/L) in pristine and combined forms on freshwater microalgae, Chlorella sp., as a model organism. The physical-chemical interactions of algal EPS (10 mg/L) with PSNPs and TPP and their mixtures were studied. The toxicity potential of the PSNPs was estimated by quantifying growth inhibition, oxidative stress, antioxidant activity, and photosynthesis in the cells. TPP toxicity increased in the presence of the PSNPs, however the addition of algal EPS reduced the combined toxic effects. EPS plays a protective role by reducing oxidative stress and enhancing photosynthetic efficiency in the algal cells. The Pearson modeling analysis indicated a positive correlation between growth inhibition, and reactive oxygen species, malondialdehyde production. The cluster heatmap and correlation mapping revealed a strong correlation among the oxidative stress, growth inhibition, and photosynthetic parameters. The study clearly highlights the potential of EPS in mitigating the risk of mixed emerging pollutants in the aquatic environment.

In vivo study of chelating agent-modified nano zero-valent iron: Biodistribution and toxicity in mice

In this study, the distribution and toxicity of nanoscale zero valent iron (nZVI) and nZVIs coated with citric acid and sodium tripolyphosphate (CA-nZVI and STPP-nZVI) in mice were investigated. nZVIs were primarily found in the livers and spleens, followed by the lungs, hearts, and kidneys. Histologic analysis revealed no significant histopathologic abnormalities or lesions in all organs except the liver at 14th d gavage. nZVIs did not have a noticeable impact on the body weight of the mice or the weight of their organs. Compared with the control group, there were no significant changes in hematology indexes in the nZVIs groups. However, the nZVIs groups exhibited varying levels of elevation in alanine aminotransferase, aspartate aminotransferase, and creatinine, suggesting liver and kidney inflammation in mice. The up-regulation of Nuclear Factor erythroid 2-Related Factor 2 and Heme oxygenase 1 in the nZVIs groups may be a response to nZVIs-induced oxidative stress. Immunohistochemical analysis confirmed the inflammatory response induced by the three nZVI groups. Chelating agents did not have a significant impact on the distribution or toxicity of nZVIs in mice. This study contributes to a comprehensive and detailed insight into nZVI toxicity in the environmental field.

Nanomaterials and biochar mediated remediation of emerging contaminants

The unrestricted release of various toxic substances into the environment is a critical global issue, gaining increased attention in modern society. Many of these substances are pristine to various environmental compartments known as contaminants/emerging contaminants (ECs). Nanoparticles and emerging sorbents enhanced remediation is a compelling methodology exhibiting great potential in addressing EC-related issues and facilitating their elimination from the environment, particularly those compounds that demonstrate eco-toxicity and pose considerable challenges in terms of removal. It provides a novel technique enabling the secure and sustainable removal of various ECs, including persistent organic compounds, microplastics, phthalate, etc. This extensive review presents a critical perspective on the current advancements and potential outcomes of nano-enhanced remediation techniques such as photocatalysis, nano-sensing, nano-enhanced sorbents, bio/phyto-remediation, which are applied to clean-up the natural environment. In addition, when dealing with residual contaminants, special attention is paid to both health and environmental implications; therefore, an evaluation of the long-term sustainability of nano-enhanced remediation methods has been considered. The integrated mechanical approaches were thoroughly discussed and presented in graphical forms. Thus, the critical evaluation of the integrated use of most emerging remediation technologies will open a new dimension in environmental safety and clean-up program.

Exfoliated MXene-AuNPs hybrid in sensing and multiple catalytic hydrogenation reactions

The increasing use of nanomaterials in consumer products is expected to lead to environmental contamination sometime soon. As water pollution is a pressing issue that threatens human survival and impedes the promotion of human health, the search for adsorbents for removing newly identified contaminants from water has become a topic of intensive research. The challenges in the recyclability of contaminated water continue to campaign the development of highly reusable catalysts. Although exfoliated 2D MXene sheets have demonstrated the capability towards water purification, a significant challenge for removing some toxic organic molecules remains a challenge due to a need for metal-based catalytic properties owing to their rapid response. In the present study, we demonstrate the formation of hybrid structure AuNPs@MXene (Mo2CTx) during the sensitive detection of Au nanoparticle through MXene sheets without any surface modification, and subsequently its applications as an efficient catalyst for the degradation of 4-nitrophenol (4-NP), methyl orange (MO), and methylene blue (MB). The hybrid structure (AuNPs@MXene) reveals remarkable reusability for up to eight consecutive cycles, with minimal reduction in catalytic efficiency and comparable apparent reaction rate constant (Kapp) values for 4-NP, MB, and MO, compared to other catalysts reported in the literature.

Regulation of SiO2 Nanoparticles on the Adsorptive Fractionation of Dissolved Organic Matter by Goethite

SiO2 nanoparticles (SiO2NPs) are most widely available and coexisting with DOM at the mineral-water interface; however, the role of SiO2NPs in DOM fractionation and the underlying mechanisms have not been fully understood. Using Fourier transform ion cyclotron resonance mass spectrometry, combined with Fourier transform infrared spectroscopy and X-ray adsorption fine structure spectroscopy, was employed to investigate the adsorptive fractionation of litter layer-derived DOM on goethite coexisting with SiO2NPs under different pH conditions. Results indicated that the inhibitory effect of the coexisting SiO2NPs on OM sorbed by goethite was waning as environmental pH increased due to the reduced steric interactions and the concurrent elevated hydrogen bonding/hydrophobic partitioning interactions on the goethite surface. We observed the coexisting SiO2NPs inhibited the adsorption of high carboxylic-containing condensed aromatic/aromatics compounds on goethite under different pH conditions while improving the adsorption of highly unsaturated aliphatic/phenolic and carbohydrate-like compounds in an alkaline and/or circumneutral environment. More nitrogen-containing structures may favor the adsorption of phenolic and nonaromatic compounds to goethite by counteracting the negative effect of SiO2NPs. These findings suggest that DOM sequestration may be significantly regulated by the coexisting SiO2NPs at the mineral-water interface, which may further influence the carbon-nitrogen cycling and contaminant fate in natural environments.

Synergistic sono-adsorption and adsorption-enhanced sonochemical degradation of dyes in water by additive manufactured PVDF-based materials

The present study proposes the first mechanistic model accounting for the most meaningful physico-chemical phenomena taking place in liquid phase adsorption processes under ultrasound. Initially, this study was aimed at developing an easy-to-make and easy-to-recover piezocatalyst for the degradation of RhB in water by combining the high piezocatalytical performance of BaTiO3 with a compatible piezoelectric support such as PVDF, manufactured by a customised additive manufacturing - direct ink writing system with in-situ poling. However, initial results showed that the resulting PVDF-BaTiO3 composite slabs performed worse than BaTiO3 piezocatalysts on their own, and that poling did not have any effect on their performance (82% RhB removal after 2 h when using either poled or unpoled PVDF-BaTiO3 composite slabs compared to 92% RhB removal after 2 h in presence of BaTiO3 piezocatalysts). Further investigation with pure PVDF materials demonstrated that, instead of piezocatalysis, synergistic ultrasound-assisted adsorption and sonochemical degradation were taking place, enabling the removal of >95% of the dye within 40 min of ultrasound treatment in the presence of 4 g L-1 of additive manufactured PVDF slabs. The results of this study and their evaluation with the mechanistic model proposed for liquid phase adsorption under ultrasound suggest that the adsorption of RhB on additive manufactured PVDF slabs was enhanced by the structure, higher specific surface ratio and higher volume of mesopores achieved through the 3D-printing process, as well as the minimisation of film resistance to mass transport due to ultrasound. Moreover, adsorption on additive manufactured PVDF enhanced the sonochemical degradation of the dye due to its high concentration in the adsorbed phase. This study demonstrates that adsorption processes, especially in the presence of PVDF materials, may be significantly more important in piezocatalysis than what has been reported to date, to the point that the synergistic combination of sono-adsorption and sonochemical degradation in presence of additive-manufactured PVDF slabs may be enough to achieve high removal rates of dyes in water.

The role of algal EPS in reducing the combined toxicity of BPA and polystyrene nanoparticles to the freshwater algae Scenedesmus obliquus

Both Bisphenol A (BPA) and polystyrene nanoplastics (PSNPs) are routinely found in several consumer products such as packaging materials, flame retardants, and cosmetics. The environment is seriously endangered by nano- and microplastics. In addition to harming aquatic life, nanoplastics (NPs) also bind to other pollutants, facilitating their dispersion in the environment and possibly promoting toxicity induced by these pollutants. The toxic effects of polystyrene nanoplastics (PS-NPs) and BPA were examined in this study, as well as the combined toxic impacts of these substances on the freshwater microalgae Scenedesmus obliquus. In addition, the exopolymeric substances (EPS) secreted by algae will interact with the pollutants modifying their physicochemical behaviour and fate. This work aimed to investigate how algal EPS alters the combined effects of BPA and PSNPs on the microalgae Scenedesmus obliquus. The algae were exposed to binary mixtures of BPA (2.5, 5, and 10 mg/L) and PSNPs (1 mg/L of plain, aminated, and carboxylated PSNPs) with EPS added to the natural freshwater medium. Cell viability, hydroxyl and superoxide radical generation, cell membrane permeability, antioxidant enzyme activity (catalase and superoxide dismutase), and photosynthetic pigment content were among the parameters studied to determine the toxicity. It was observed that for all the binary mixtures, the carboxylated PSNPs were most toxic when compared to the toxicity induced by the other PSNP particles investigated. The maximum damage was observed for the mixture of 10 mg/L of BPA with carboxylated PSNPs with a cell viability of 49%. When compared to the pristine mixtures, the EPS-containing mixtures induced significantly reduced toxic effects. A considerable decrease in reactive oxygen species levels, activity of antioxidant enzymes (SOD and CAT), and cell membrane damage was noted in the EPS-containing mixtures. Reduced concentrations of the reactive oxygen species led to improved photosynthetic pigment content in the cells.

Environmental impact assessment of nanofluids containing mixtures of surfactants and silica nanoparticles

Due to widespread use of nanoparticles in surfactant-based formulations, their release into the environment and wastewater is unavoidable and toxic for biota and/or wastewater treatment processes. Because of concerns over the environmental impacts of nanofluids, studies of the fate and environmental impacts, hazards, and toxicities of nanoparticles are beginning. However, interactions between nanoparticles and surfactants and the biodegradability of these mixtures have been little studied until now. In this work, the environmental impacts of nanofluids containing mixtures of surfactants and silica nanoparticles were valuated. The systems studied were hydrophilic silica nanoparticles (sizes 7 and 12 nm), a nonionic surfactant (alkyl polyglucoside), an anionic surfactant (ether carboxylic acid), and mixtures of them. The ultimate aerobic biodegradation and the interfacial and adsorption properties of surfactants, nanoparticles, and mixtures during biodegradation were also evaluated. Ultimate biodegradation was studied below and above the CMCs of the individual surfactants. The interfacial and adsorption properties of surfactant solutions containing nanoparticles were influenced by the addition of silica particles. It was determined that silica nanoparticles reduced the capability of the nonionic surfactant alkyl polyglucoside to decrease the surface tension. Thus, silica NPs promoted a considerable increase in the surfactant CMC, whereas the effect was opposite in the case of the anionic surfactant ether carboxylic acid. Increasing concentrations of surfactant and nanoparticles in the test medium caused decreases in the maximum levels of mineralization reached for both types of surfactants. The presence of silica nanoparticles in the medium reduced the biodegradability of binary mixtures containing nonionic and anionic surfactants, and this effect was more pronounced for larger nanoparticles. These results could be useful in modelling the behaviour of nanofluids in aquatic environments and in selecting appropriate nanofluids containing nanoparticles and surfactants with low environmental impact.

Advanced sanitation products infused with silver nanoparticles for viral protection and their ecological and environmental consequences

The outbreak of coronavirus ailments (COVID-19) in 2019 resulted in public health crisis leading to global pandemonium. In response to the high prevalence of disease transmission, governments all around the globe implemented emergency measures in various routes (e.g., social distancing, personal hygiene, and disinfection of public/private places) to curb/contain COVID-19 infections. The social media infodemic, released as uncensored publishing and/or views/recommendations, also triggered large-scale behavior changes such as the overuse of advanced sanitation products (ASPs) containing nanomaterials. The majority of these ASPs contain silver nanoparticles (AgNPs) as an active ingredient to enhance their antimicrobial potential. Ecotoxicological concerns such as the transformation and degradation of these AgNP-infused products in terrestrial or aquatic environments are under the jurisdiction of the EPA. However, they are not considered in the FDA approval process. In light of excessive consumption of ASPs, it is time to consider their ecotoxicological screening prior to market approval jointly by the FDA and EPA, along with the implementation of post-market surveillance strategies. At the same time, efforts should be put into running awareness programs to prevent the overuse of ASPs.

The impact of engineered nanomaterials on the environment: Release mechanism, toxicity, transformation, and remediation

The presence and longevity of nanomaterials in the ecosystem, as well as their properties, account for environmental toxicity. When nanomaterials in terrestrial and aquatic systems are exposed to the prevailing environmental conditions, they undergo various transformations such as dissociation, dissolution, and aggregation, which affects the food chain. The toxicity of nanomaterials is influenced by a variety of factors, including environmental factors and its physico-chemical characteristics. Bioaccumulation, biotransformation, and biomagnification are the mechanisms that have been identified for determining the fate of nanomaterials. The route taken by nanomaterials to reach living cells provides us with information about their toxicity profile. This review discusses the recent advances in the transport, transformation, and fate of nanomaterials after they are released into the environment. The review also discusses how nanoparticles affect lower trophic organisms through direct contact, the impact of nanoparticles on higher trophic organisms, and the possible options for remediation.

Bio-fabricated silver nanoparticles for controlling dengue and filaria vectors and their characterization, as well as toxicological risk assessment in aquatic mesocosms

The present study is focused on synthesis of silver nanoparticles from weeds and an assessment of their mosquito larvicidal efficacy. This study also presented the toxicological effects as well as the stability of these nanoparticles in aquatic mesocosms. The weed Digiteria sanguinallis was first time used for the synthesis of silver nanoparticles. The synthesized nanoparticles were characterized by various analytical techniques, such as UV-VIS, TEM, FESEM, EDX, XRD, FTIR, and zeta potential study. The result revealed that the nanoparticles are crystalline, spherical shape with band gap 2.44 eV, and average size 18 nm. The LC₅₀ value of synthesized AgNPs were recorded as 7.47 and 6.31 mg/L at 24 h against Cx. quinquefasciatus and A. albopictus respectively. In contrast, larvicidal activity of weed extract was insignificant against two target species. In aquatic mesocosm study, AgNPs (LC₅₀ dose) does not alter the nature of water parameters within experimental period. However only EC % and ORP were changes because of silver ion oxidation. In biochemical parameters, only stress enzymes for animal and plant species were moderately altered under long term exposure. But glycogen, protein, and AchE of two mosquito species were significantly changed under same mesocosm setup within short exposure. Comparatively, in control mesocosm, synthesized AgNPs are naturally change their nano form within 20 days with the presence of all non-target species and pond sediment. Therefore, it can be concluded that biosynthesized AgNPs could be used as a larvicidal agent in near future with negligible effects on aquatic organisms.

Environmental Fate of Metal Nanoparticles in Estuarine Environments

In the last decade, metal engineered nanomaterials (ENMs) have seen an exponential use in many critical technologies and products, as well an increasing release into the environment. Coastal ecosystems worldwide may receive ENM-polluted waters and wastes, with a consequent alteration of habitats and contamination of aquatic biota. There is a scarcity of data regarding the fate of these emerging contaminants in such environments. Open issues include the determination of the sources, the quantification of the interactions with marine sediments, the bioaccumulation pathways, the ecotoxicology on marine fauna and the identification of the principal biotic and abiotic factors that may alter metal ENMs toxicity. Little is known about their potential transference into the food web, as well toxicity features and co-stressors of single or multiple ENMs under laboratory and real environmental conditions for various taxonomic phyla. This review reports current knowledge on the ecological impact of ENMs under the complex environmental conditions of estuary systems, identifies gaps in current knowledge and provides directions for future research.

A Review on Emerging Pollutants in the Water Environment: Existences, Health Effects and Treatment Processes

Emerging pollutants (EPs), also known as micropollutants, have been a major issue for the global population in recent years as a result of the potential threats they bring to the environment and human health. Pharmaceuticals and personal care products (PPCPs), antibiotics, and hormones that are used in great demand for health and cosmetic purposes have rapidly culminated in the emergence of environmental pollutants. EPs impact the environment in a variety of ways. EPs originate from animal or human sources, either directly discharged into waterbodies or slowly leached via soils. As a result, water quality will deteriorate, drinking water sources will be contaminated, and health issues will arise. Since drinking water treatment plants rely on water resources, the prevalence of this contamination in aquatic environments, particularly surface water, is a severe problem. The review looks into several related issues on EPs in water environment, including methods in removing EPs. Despite its benefits and downsides, the EPs treatment processes comprise several approaches such as physico-chemical, biological, and advanced oxidation processes. Nonetheless, one of the membrane-based filtration methods, ultrafiltration, is considered as one of the technologies that promises the best micropollutant removal in water. With interesting properties including a moderate operating manner and great selectivity, this treatment approach is more popular than conventional ones. This study presents a comprehensive summary of EP’s existence in the environment, its toxicological consequences on health, and potential removal and treatment strategies.

Surfactant free synthesis of cationic nano-vesicles: A safe triple drug loaded vehicle for the topical treatment of cutaneous leishmaniasis

The basic aim of the study was to develop and evaluate the triple drug loaded cationic nano-vesicles (cNVs), where miltefosine was used as a replacement of surfactant (apart from its anti-leishmanial role), in addition to meglumine antimoniate (MAM) and imiquimod (Imq), as a combination therapy for the topical treatment of cutaneous leishmaniasis (CL). The optimized formulation was nano-sized (86.2±2.7nm) with high entrapment efficiency (63.8±2.1% (MAM) and 81.4±2.3% (Imq)). In-vivo skin irritation assay showed reduced irritation potential and a decrease in the cytotoxicity of cNVs as compared to conventional NVs (having sodium deoxycholate as a surfactant). A synergistic interaction between drugs was observed against intracellular amastigotes, whereas the in-vivo antileishmanial study presented a significant reduction in the parasitic burden. The results suggested the potential of surfactant free, triple drug loaded cNVs as an efficient vehicle for the safe topical treatment of CL.

Ecotoxicological effects of new generation pollutants (nanoparticles, amoxicillin and white musk) on freshwater and marine phytoplankton species

Phytoplankton occupies a key trophic level in aquatic ecosystems. Chemical impacts on these primary producers can disrupt the integrity of an entire ecosystem. Two freshwater (Pseudokirchneriella subcapitata-Ps and Scenedesmus obliquus-S) and three marine (Phaeodactylum tricornutum-P, Isochrysis galbana-I, Tetraselmis suecica-T) microalgae species were exposed to dilutions of four chemicals: nanoparticles (n-TiO₂, n-ZnO), amoxicillin (antibiotic), and white musk (personal care fragrance) to determine the half maximal effective concentration (EC₅₀) after 72 h of exposure under standardized and controlled environmental conditions. Cell cultures were exposed to EC₅₀ to determine sublethal effects (72 h) based on biochemical (chlorophylls a, b, c), molecular (changes in outer cell wall structure), and morphological alterations. We report for the first time EC₅₀ values for nanoparticles in not standardized species (S, I and T) and for amoxicillin and white musk in all tested species. Standardized species (Ps and P) were less sensitive than non-standardized in some cases. Fourier-transformed infrared spectroscopy showed a marked spectral alteration (from 10.44% to 90.93%) of treated cultures compared to negative controls; however, principal component analysis disclosed no differences in molecular alteration between the five microalgae species or the two aquatic habitats considered. There was a significant decrease in chlorophylls content in all species exposed to EC₅₀ compared to controls (Kruskal Wallis test; p < 0.05). There was a significant increase in cell-size (Mann-Whitney U test; p < 0.05) in I, P and T exposed to white musk and S exposed to amoxicillin. Findings highlight ecotoxicological risks from new generation pollutants for primary producers in aquatic ecosystems.

Comparison of biomarker responses after acute and chronic bioassays in Lumbriculus variegatus

Differential biomarker responses may occur after acute or chronic bioassays when animals are unfed. In many aquatic species, food deprivation may lead to a pro-oxidant condition. However, information about its effects on the oligochaete Lumbriculus variegatus, a bioindicator organism for water and sediment toxicity tests, is almost completely lacking. Acute (48 h) and chronic (21 days) bioassays were performed using unfed L. variegatus to assess the impact of food deprivation on several biomarkers related to the redox cellular status. Results showed that food deprivation inhibited the antioxidant enzymes superoxide dismutase and catalase, whilst levels of total glutathione (t-GSH) and lipid peroxidation processes increased with respect to controls. The same biomarkers were evaluated in unfed organisms exposed to tributyltin (TBT), nano-goethite or a binary mixture of both, for 48 h and 21 days. After 48 h, the organisms were able to cope with chemical stressors by enhancing antioxidant defences and lipid peroxidation processes were not observed. After 21 days, both TBT and the binary mixture induced the most noxious effects. At this time, the antioxidant enzymatic defences were still higher than controls, but levels of t-GSH were significantly decreased and lipid peroxidation was found. Therefore, differential biomarker responses were observed between starved organisms for 21 days and those simultaneously exposed to other chemical stressors. The activity of the enzyme acetylcholinesterase was also determined, but it remained unchanged in all cases.

The impacts of metal-based engineered nanomaterial mixtures on microbial systems: A review

The last decade has witnessed tremendous growth in the commercial use of metal-based engineered nanomaterials (ENMs) for a wide range of products and processes. Consequently, direct and indirect release into environmental systems may no longer be considered negligible or insignificant. Yet, there is an active debate as to whether there are real risks to human or ecological health with environmental exposure to ENMs. Previous research has focused primarily on the acute effects of individual ENMs using pure cultures under controlled laboratory environments, which may not accurately reveal the ecological impacts of ENMs under real environmental conditions. The goal of this review is to assess our current understanding of ENM effects as we move from exposure of single to multiple ENMs or microbial species. For instance, are ENMs' impacts on microbial communities predicted by their intrinsic physical or chemical characteristics or their effects on single microbial populations; how do chronic ENM interactions compare to acute toxicity; does behavior under simplified laboratory conditions reflect that in environmental media; finally, is biological stress modified by interactions in ENM mixtures relative to that of individual ENM? This review summarizes key findings and our evolving understanding of the ecological effects of ENMs under complex environmental conditions on microbial systems, identifies the gaps in our current knowledge, and indicates the direction of future research.

Quo Vadis, Nanoparticle-Enabled In Vivo Fluorescence Imaging?

The exciting advancements that we are currently witnessing in terms of novel materials and synthesis approaches are leading to the development of colloidal nanoparticles (NPs) with increasingly greater tunable properties. We have now reached a point where it is possible to synthesize colloidal NPs with functionalities tailored to specific societal demands. The impact of this new wave of colloidal NPs has been especially important in the field of biomedicine. In that vein, luminescent NPs with improved brightness and near-infrared working capabilities have turned out to be optimal optical probes that are capable of fast and high-resolution in vivo imaging. However, luminescent NPs have thus far only reached a limited portion of their potential. Although we believe that the best is yet to come, the future might not be as bright as some of us think (and have hoped!). In particular, translation of NP-based fluorescence imaging from preclinical studies to clinics is not straightforward. In this Perspective, we provide a critical assessment and highlight promising research avenues based on the latest advances in the fields of luminescent NPs and imaging technologies. The disillusioned outlook we proffer herein might sound pessimistic at first, but we consider it necessary to avoid pursuing "pipe dreams" and redirect the efforts toward achievable-yet ambitious-goals.

Developmental neurotoxicity fingerprint of silica nanoparticles at environmentally relevant level on larval zebrafish using a neurobehavioral-phenomics-based biological warning method

BACKGROUND

Larval zebrafish (Danio rerio) is not only an ideal vertebrate applied in Fish Embryos Toxicity (FET) test but also a well-accepted model in behavioral neurotoxicity research. By applying the commercial standard behavioral tracking system (Zebrabox), the locomotion profiles (neurobehavioral-phenomics) of larval zebrafish can be comprehensively monitored and systematically analyzed to probe ecotoxicological neurotoxicity of nano-pollutants at environmental relevant concentration level.

RESULTS

Herein, the potential toxicity of at environment relevant concentration level on embryonic zebrafish was evaluated by FET and neurobehavioral-phenomics (NBP). The embryos were exposed to the environmental relevant concentration (0.05, 0.1,1, 5, 10, 100 μg/L). The FET criteria were utilized to evaluate the ecotoxicological effect induced by silica NPs. Subsequently, behavioral neurotoxicity of silica NPs was further quantified via locomotion response (LMR). Specifically, the alteration of Light/Dark challenge (LDC) evoked by light/dark stimulation was detected and analyzed by commercially standard behavioral protocols using zebrabox. We revealed that the exposures of silica NPs at environmental relevant concentration (0.05, 0.1, 1, 5, 10,100 μg/L) significantly disturbed locomotion profiles of larval zebrafish. Additionally, it was obviously noted that low, environmentally relevant silica concentrations might result in altering the total behavioral profiles in developing zebrafish.

CONCLUSIONS

In sum, neurobehavior phenomics profiling based on LMR and LDC is a potent methodology for the evaluation of sub-lethal or sub-teratogenic toxicity. Compared with the FET tests characterized by the detection of embryonic teratogenicity, the neurobehavior phenomics based method can be more sensitive to determine sub-teratogenic toxicity of silica NPs at environmental concentrations. With the combination of multivariate data analysis, this approach would offer effective technical reference for environmental nano-toxicology research.

Highly efficient removal of silver nanoparticles by sponge-like hierarchically porous thiourea-formaldehyde resin from Water

With the increasing production and rapid market penetration as well as the confirmation of the toxic effects, silver nanoparticles (AgNPs) are one kind of newly emerging environmental contaminants of high concern. It is urgent to develop the efficient method to remove them from the environment. In this study, the sponge-like hierarchically porous thiourea-formaldehyde (TF) resin rich with nitrogen and sulfur was for the first time proposed as the adsorbent to achieve this goal. With enormous interconnected layer structure and plentiful macropores, the porous TF resin provided abundant available interaction sites and fast mass transfer to adsorb citrate stabilized AgNPs (citrate-AgNPs). Fast adsorption rate and high adsorption capacity (2478 mg/g) were obtained based on the electrostatic and metal-ligand interactions. Heterogeneous aggregation and simultaneous adsorption contributed to this removal process. Furthermore, with the assistance of NaCl, the porous TF resin exhibited largely enhanced removal efficiency towards citrate-AgNPs up to 98.7 % in 5 min, possibly due to the co-operation of adsorption and coagulation. This study proposed a promising adsorbent to remove AgNPs and provided a referential strategy to design highly efficient adsorbents for removal of nanoparticles.

Carbon family nanomaterials — new applications and technologies

Research on carbon-based nanomaterials (CBNMs) and their development is one of the major scientific disciplines of the last century. This is mainly because of their unique properties which can lead to improvements in industrial technology or new medical applications. Therefore, it is necessary to examine their properties such as shape, size, chemical composition, density, toxicity, etc. This article focuses on the general characteristics of nanomaterials (NMs) and their behavior when entering the environment (water and soil). In addition, it presents individual members of the graphene family including porous ecological carbon (biochar). The article mainly deals with the new potential technologies of CBNMs considering their possible toxic and genotoxic effects. This review also highlights the latest developments in the application of self-propelled micromotors for green chemistry applications. Finally, it points to the potential biomedical applications of CBNMs.

Removal of Chromium from Synthetic Wastewater Using Modified Maghemite Nanoparticles

The main aim of this study was to ascertain the removal of chromium ions from synthetic wastewater using modified maghemite nanoparticles (MNPs). Commercially available maghemite nanoparticles (NPs) (< 50 nm) were modified using sodium dodecyl sulfate (SDS). The MNPs were characterized using a powder X-ray diffractometer (XRD) and Fourier transform infrared spectrophotometer (FTIR). Statistically designed batch experiments were carried out to evaluate the effects of various parameters, namely the pH of the solution, initial chromium concentration, and adsorbent dose, on the chromium removal efficiency (RE). The results from this study showed that the adsorbent dose had a synergistic effect on chromium RE, while pH and initial chromium concentration had antagonistic effects on the RE. An optimal chromium RE of 95.8% was obtained at pH = 2.6, adsorbent dose = 5 g/L, and initial chromium concentration = 20 mg/L. The analysis of variance (ANOVA) results showed that the model was significant, with high F value (F = 80.07) and low P value (P = < 0.001). Based on the results obtained from the experiments, the MNPs could be exploited as an efficient adsorbent for chromium removal from wastewater.

Polysaccharides derived from Enteromorpha prolifera for the removal of silver nanoparticle-humic acid contaminants by a coagulation-ultrafiltration process

Silver nanoparticles (AgNPs) pose serious health risks to humans as the adsorption between AgNPs and humic acid (HA) makes it difficult to remove them from surface water. To solve this problem, polysaccharides extracted from a marine alga, Enteromorpha prolifera (denoted as Ep), were used to eliminate the AgNP–HA composite contaminant via a coagulation-ultrafiltration (C-UF) process. The structure of Ep, AgNP–HA removal mechanism and membrane fouling were analyzed. The results indicated that the backbone of Ep was composed of (1 → 4)-linked l-rhamnopyranose, (1 → 4)-linked d-xylose and (1 → 4)-linked glucuronic acid. With the charge neutralization of PAC hydrolysates and the bridging-sweep role of Ep, AgNPs could be removed completely by the C-UF process. The coagulation performance and membrane flux were the highest when the PAC and Ep dosages were 2.0 mg L⁻¹ and 0.3 mg L⁻¹, respectively. In addition, when Ep was applied in the C-UF process, the flocs exhibited larger sizes, faster growth rates, better recovery ability and looser structures, which resulted in lower cake resistance and less pore blocking of the UF membrane. Consequently, the membrane flux could be improved by about 25–30% due to the addition of Ep.

Applying Ep as a coagulant aid in C-UF process could simultaneously remove AgNPs and reduce membrane fouling.

Synchronous removal of CuO nanoparticles and Cu2+ by polyaluminum chloride-Enteromorpha polysaccharides: Effect of Al species and pH

Copper oxide nanomaterials have been extensively applied and can have serious impacts when discharged into the aquatic environment, especially when complexed with humic acid (HA) to form composite contaminants. As an innovative recycled coagulant aid, Enteromorpha polysaccharides (Ep) were associated with polyaluminum chloride (PACl) (denoted as PACl-Ep) to simultaneously remove CuO nanoparticles, Cu²⁺ and HA in this study. The influence of different Al species coagulants (AlCl₃, PACl_b and PACl_c) and water pH on coagulation performance, floc properties and reaction mechanisms was investigated in detail. Results showed that in the three PACl-Ep systems, PACl_b-Ep gave the highest removal efficiencies for turbidity and Cu²⁺, and the best UV₂₅₄ removal effect was reached by using PACl_c-Ep. Higher contents of Al_b and Al_c contributed to great coagulation performance because of their stronger bridging and sweeping effects. For all the Al species coagulants, alkalescent conditions were more conducive to removing Cu and HA compared to acidic conditions. Additionally, smaller and more agminated flocs with great recovery ability were formed by PACl_b-Ep and PACl_c-Ep systems (bridging and enmeshment effects cooperated with the chelated reticular structure formed by the Ep and Al species). Similarly, due to the increased hydrolysis and hydroxide precipitates, flocs formed under the condition of alkalescence were smaller, denser and stronger compared with weakly acidic conditions.

Ecotoxicity of nano-metal oxides: A case study on daphnia magna

In Europe REACH framework directive imposes data acquisition concerning toxicity on acquatic species before the commercialization of chemicals to assess environmental risks. According to official methods, exposure tests are performed under in vitro and standardized conditions: OECD's guideline rules external variables such as water type, feeding conditions, and exposure time. As consequence, such obtained results could be different from effects observed in natural environments. This study collects effects within 24-96 h of exposure to nano metal-oxides (ZnO, TiO₂) on D. magna obtained by the exposure under standard OECD conditions comparing them with results obtained by the exposure under more similar conditions to natural environment (i.e. mixture, feeding). High doses exposure determines gas-bubble disease. Animals exposed to LC10 actively ingest nanoparticles under both fasting and feeding conditions. Furthermore, body burial by a coat of nanoparticles thicker in mixtures than in single dispersions was recorded. Furthermore, results show that: (i) effects increase over time; (ii) n-ZnO results less effective than n-TiO₂ in both single dispersion, and mixture; (iii) the presence of surfactant increases toxicity of nanoparticles; (iv) immobilization is a more sensitive endpoint than mortality; (v) feeding increases test sensitiveness improving differences among treated and controls till 96 h and allowing longer exposure times than standard OECD test. As general remark, this study provides evidence that in vitro ecotoxicological results obtained under standardized OECD conditions could be significant different to animals' responses under natural (feeding and mixtures) exposure conditions.

Silver nanoparticles reduced the invasiveness of redroot pigweed

The differences in the growth performance between invasive species and native species might paly a key role in the effective invasion. The extensive use of silver nanoparticles (AgNPs) has created the concern of their release into environment. Thus, the possible effects of AgNPs on the growth performance of invading agents are critical to better illustrate the underlying mechanisms for effective invasion. This study aimed to assess the impacts of AgNPs with different concentrations [200 and 400 mg kg (soil)^-1] and particle sizes (30 and 70 nm) on the growth performance and competitive ability of well known invasive Amaranthus retroflexus L. (redroot pigweed) and native A. tricolor L. (red amaranth). It was observed that the growth characteristics and supporting ability of redroot pigweed were significantly lower than those of amaranth. Results of the relative competitive intensity index and the relative dominance index also revealed that redroot pigweed exhibited lower competitive ability compared to red amaranth, especially under AgNPs. It can be assumed that the poor growth performance and competitive ability of redroot pigweed might prevent its invasiveness under AgNPs. The supporting ability, leaf photosynthetic area, leaf growing ability, leaf resource use efficiency and acquisition capability, and growth competitiveness of the two plant species were found to be significantly reduced under AgNPs. AgNPs with 30 nm at 400 mg kg (soil)^-1 triggered more toxicity on the supporting ability and growth competitiveness of the two plant species than AgNPs with 30 nm at 200 mg kg (soil)^-1. In addition, AgNPs with 30 nm imparted high toxicity on the leaf growing ability of red amaranth than AgNPs with 70 nm. However, the particle size of AgNPs did not address significant effects on the growth performance of redroot pigweed. Ag⁺ solution exhibited stronger toxicity on the supporting ability and leaf growing ability of the two plant species than AgNPs.

Bioaccumulation and toxic effects of nanoparticulate and ionic silver in Saccostrea glomerata (rock oyster)

The increasing production of Ag nanoparticle (AgNP) containing products has inevitably led to a growing concern about their release into the aquatic environment, along with their potential behaviour, toxicity, and bioaccumulation in marine organisms exposed to NPs released from these products. Hence, this study is focused on the effects of AgNPs in Saccostrea glomerata (rock oyster) in artificial seawater (ASW); evaluating the NP's stability, dissolution, and bioaccumulation rate. AgNPs NM300K (20 ± 5 nm) in concentrations of 12.5 μgL^-1 and 125 μgL^-1 were used to conduct the experiments, and were compared to a blank and a positive control of 12.5 μgL^-1 AgNO₃. Dissolution in ASW was measured by ICP-OES and stability was assessed by TEM after 1 h and 3, 5, and 7 days of exposure. Bioaccumulation in gills and digestive glands was measured after 7 days of exposure. The higher concentration of AgNPs induced more aggregation, underwent less dissolution, and showed less bioaccumulation, while the lower concentration showed less aggregation, more dissolution and higher bioaccumulation. Five biomarkers (EROD: ethoxyresorufin-o-deethylase, DNA strand breaks, LPO: lipid peroxidation, GST: glutathione S-transferase and GR: glutathione reductase) were analysed at 0, 3, 5 and 7 days. Significant differences compared to the initial day of exposure (day 0) were reported in DNA strand breaks after 5 and 7 days of exposure, GST, from the third day of exposure, in all the Ag samples, and in some samples for LPO and GR biomarkers, while no significant induction of EROD was observed. A combined effect for each type of treatment and time of exposure was also reported for DNA strand breaks and GST biomarkers measured at the digestive glands. In general, the significant inductions measured showed the following trend: 125 μgL^-1 AgNPs >12.5 μgL^-1 AgNPs ∼12.5 μgL^-1 AgNO₃ even though bioaccumulation followed the opposite trend.

Simultaneous removal of nitrogen and phosphorous by heterotrophic nitrification-aerobic denitrification of a metal resistant bacterium Pseudomonas putida strain NP5

A novel strain NP5 with efficient heterotrophic nitrification, aerobic denitrification and phosphorus accumulation ability was isolated and identified as Pseudomonas putida strain NP5. The removed ammonium and phosphate were mainly converted into intracellular components by assimilation, and negligible nitrification intermediates and N₂O were accumulated during heterotrophic nitrification. In addition, the optimal conditions for nutrient removal were: succinate as carbon source, C/N 10, P/N 0.2, temperature 30 °C, salinity 0% and shaking speed 160 rpm. Besides, strain NP5 possessed an exceptional heavy metal and nanoparticles resistance. Cr⁶⁺ was found to be the most toxic among the tested metals, and it could be removed simultaneously. Moreover, an obvious phosphorus release was observed under anaerobic condition, and repeated exposure to the anaerobic/aerobic conditions could significantly improve the nutrient removal. Furthermore, the successful expression of key enzymes for nitrogen and phosphorous removal provided additional evidence for possibility of simultaneous nitrification, denitrification and phosphorus removal.

Incidence and persistence of silver nanoparticles throughout the wastewater treatment process

While the predicted or observed concentrations of Ag NPs in wastewater treatment plants (WWTPs) have ranged from μg/L to ng/L, there is still uncertainty with regards to the realistic concentration range of Ag NPs in WWTPs. In addition, the persistence, removal, and size of Ag NPs throughout WWTP process is also not well investigated, particularly in real operating conditions. In this study, the incidence and persistence of Ag NPs in the wastewater process were studied by using single particle inductively coupled plasma mass spectrometry (sp-ICP-MS). The incidence of Ag NPs was determined in samples collected at the influent and effluent of the conventional process, as well as reclaimed and backwash waters of the ultrafiltration (UF) system in a WWTP (Santa Barbara, CA), showing a concentration of 13.5, 3.2, 0.5 and 9.8 ng/L, respectively, with relative standard deviations (RSDs) < 5%. Total Ag concentration (Ag NP and Ag⁺) ranged from 40 to 70 ng/L, in line with lower predicted values. Most of the Ag NPs detected were below 100 nm, with a few above 100 nm in the conventional effluent. Biological and physical processes in the secondary treatment removed 76.3% of the colloidal Ag fraction, while with the tertiary treatment (UF) the WWTP achieved a removal of 96.3% of the colloidal fraction. Persistence of Ag NPs in various water matrixes, including a synthetic wastewater (SWW), was determined by spiking 300 ng/L of Ag NPs (40 nm) and monitoring the concentrations and size change for 15 days. The persistence of Ag NPs in suspension was Influent > Effluent > Reclaimed > SWW. Partial dissolution of NPs in all waters was observed from time 0 h. Although the current concentrations in the outlet flows from WWTP (effluent and reclaimed waters) were low, the presence of small and stable Ag NPs may raise ecotoxicological concerns via bioaccumulation.

Polyaluminum chloride-functionalized colloidal gas aphrons for flotation separation of nanoparticles from water

The present work used the coagulative colloidal gas aphron (CCGA)-involved flotation as a robust technology to efficiently remove the typical engineered nanoparticles - silica nanoparticles (SNPs) from water. The inorganic polymer coagulant - polyaluminum chloride (PACl) was used to surface-functionalize the zwitterionic surfactant (C15B)-based CGAs. Results denote that the physicochemical conditions of PACl/C15B mixed solution markedly influenced the flotation behaviors by changing the properties of CCGAs. The C15B molecules showed different dissociated states and interaction behaviors with Al species with the variation of pH. The addition of salt into the PACl/C15B mixed solution decreased the foamability of solution, and the bubbles collapsed before they could efficiently capture SNPs in their rising trajectory. The optimum SNP removal (87.2%) was obtained when the pH and the additional ionic strength of PACl/C15B mixed solution were ∼4.7 and ≤ 1.0 g NaCl/L, individually, and the pH of SNP suspension was ∼9.4. Importantly, modifying PACl on microbubbles took greater advantages than directly using it as coagulant in terms of SNP removal and PACl utlization. The CCGAs were robust since their colloidal attraction and collision efficiency with SNPs were simultaneously enhanced. The PACl was more efficiently utilized during flotation whilst the regular chemical-dosing unit was omitted.

Lead Remediation Using Smart Materials. A Review

The nanoparticles have been prepared and employed as excellent adsorbents for the sequestration of heavy metal ions and hazardous impurities from the aqueous media. The surface morphological, textural and structural properties of nanoparticles have been modified, which are capable and potentially useful for the remediation of metal ions. Several metals (oxides, doped, nanocomposites of Fe, Ti, Zn, SiO2, SiC, Mo, Co, Ni, Zr, Mn, Si, S, Al, Cu, Ce, graphene, CNTs) were reported an efficient adsorbents for the removal of lead (Pb) ions from aqueous media and polluted water. The present review focuses on different kinds of nanoparticles such as metal oxides, carbon based and host supported employed for removal of Pb ions under varying experimental conditions such as pH, temperature, contact time and concentrations. The preparation strategies, physicochemical properties and adsorption are also discussed. Based on studies, it was found that the smart materials are affective adsorbents for the purification of wastewater containing Pb ions and could possibly extended for the remediation of other heavy metal ions.

Application of Enteromorpha polysaccharides as a new coagulant aid to remove silver nanoparticles: role of dosage sequence and solution pH

Silver nanoparticles (AgNPs) in surface water cause a serious threat to the health of humans and aquatic organisms. However, it is difficult to remove AgNPs completely since they could adsorb onto the surface of humic acid (HA) and meanwhile release Ag⁺ into water. In this paper, Enteromorpha polysaccharides (Ep) were applied as a coagulant aid with polyaluminum chloride (PAC) to solve this problem. The influences of Ep dosage, dosing sequence and solution pH on the coagulation efficiency, kinetics and removal mechanism of AgNPs were discussed systematically. Results showed that when Ep was applied, AgNPs could be removed effectively due to charge neutralization of PAC hydrolysate and the bridging-sweeping role of Ep gel network. When Ep was added 30 s after PAC dosing, the coagulation efficiency was about 10–20% higher than that of the reverse order. Under this condition, flocs sizes achieved 450 μm when the solution pH was 6.0, which is much larger than that using Ep–PAC. Additionally, Ep showed an ability to promote the re-aggregation of broken flocs, and AgNP–HA flocs exhibited larger sizes, better shear resistance, higher recovery ability and denser structure at pH 6.0. Factorial analysis results indicated that PAC dosage had the greatest impact on HA and AgNP removal, while Ag⁺ removal is more sensitive to Ep dosage.

Silver nanoparticles (AgNPs) could be removed effectively due to bridging-sweep role of Enteromorpha polysaccharides (Ep), and flocs exhibited larger sizes, better shear resistance, higher recovery ability and denser structure when Ep was added.

Silver nanoparticles with different particle sizes enhance the allelopathic effects of Canada goldenrod on the seed germination and seedling development of lettuce

Allelopathic effects on the seed germination and seedling development of co-occurring native plant species (natives hereafter) are regarded as an important driver facilitating invasion of many invasive plant species (invaders hereafter). The release of silver nanoparticles (AgNPs) into the environment may affect the allelopathic effects of the invaders on the seed germination and seedling development of natives. This study aims to assess the allelopathic effects (using leaf extracts) of Canada goldenrod (Solidago canadensis L.) on the seed germination and seedling development of native lettuce (Lactuca sativa L.) treated with AgNPs with different particle sizes. Canada goldenrod leaf extracts with high concentration exhibit stronger allelopathic effects on the seedling height and root length of lettuce than those treated with low concentration. AgNPs of all particle sizes significantly decreased seed germination and seedling development indices of lettuce. AgNPs with larger particle sizes exerted stronger toxicity on leaf length and width of lettuce than those with smaller particle sizes. Thus, nanoparticles with larger particle sizes might mediate the production of increased sizes of cell wall pore size and large absorption of such substances by plant roots can be harmful. AgNPs significantly enhanced the allelopathic effects of Canada goldenrod on the seed germination and seedling development of lettuce. Small particle size AgNPs may play a more essential role in the enhanced allelopathic effects of low concentrations of Canada goldenrod leaf extracts; however, large particle size AgNPs may play a more important role in the enhanced allelopathic effects of high concentrations of Canada goldenrod leaf extracts.

Simultaneous Multidrop Creation with Superhydrophobic Wells for Field Environmental Sensing of Nanoparticles

Facile creation of multiple drops at appropriate volumes on surfaces without the use of sophisticated instrumentation facilitates downstream evaporative preconcentration of liquid samples for analytical purposes. In this work, a superhydrophobic (SH) substrate comprising wells with a perforated mesh base was developed for simultaneous drop creation in a quick and convenient manner. In contrast to the method of pouring liquid directly over the SH wells, consistent liquid filling was readily achieved by a simple immersion approach. This method works well even for challenging situations where well diameters are smaller than 3.4 mm. Despite the poor liquid-retention properties of SH surfaces, inverting the wells did not result in liquid detachment under gravitational force, indicating strong pinning effects afforded by the well architecture. The perforated base of the well allowed the liquid to be completely removed from the well by compressed air. High-speed camera image processing was used to study the evolution of drop contact angle and displacement with time. It was found that the liquid body was able to undergo strong oscillations. Optical spectroscopy was used to confirm the ability of evaporative preconcentration of silver nanoparticles.

Silica micro- and nanoparticles reduce the toxicity of surfactant solutions

In this work, the toxicity of hydrophilic fumed silica micro- and nanoparticles of various sizes (7 nm, 12 nm, and 50 μm) was evaluated using the luminescent bacteria Vibrio fischeri. In addition, the toxicity of an anionic surfactant solution (ether carboxylic acid), a nonionic surfactant solution (alkyl polyglucoside), and a binary (1:1) mixture of these solutions all containing these silica particles was evaluated. Furthermore, this work discusses the adsorption of surfactants onto particle surfaces and evaluates the effects of silica particles on the surface tension and critical micellar concentration (CMC) of these anionic and nonionic surfactants. It was determined that silica particles can be considered as non-toxic and that silica particles reduce the toxicity of surfactant solutions. Nevertheless, the toxicity reduction depends on the ionic character of the surfactants. Differences can be explained by the different adsorption behavior of surfactants onto the particle surface, which is weaker for nonionic surfactants than for anionic surfactants. Regarding the effects on surface tension, it was found that silica particles increased the surface activity of anionic surfactants and considerably reduced their CMC, whereas in the case of nonionic surfactants, the effects were reversed.

Silver engineered nanoparticles in freshwater systems - Likely fate and behaviour through natural attenuation processes

Growth in the nanotechnology sector is likely introducing unnatural formations of materials on the nanoscale (10^-9m) to the environment. Disposal and degradation of products incorporating engineered nanomaterials (ENMs) are likely being released into natural aquatic systems un-intentionally primarily via waste water effluents. The fate and behaviour of metallic based nanoparticles (NPs) such as silver (Ag) in aquatic waters is complex with high levels of variability and uncertainty. In-situ physical, biological and chemical (natural attenuation) processes are likely to influence ENM fate and behaviour in freshwater systems. Surfaced functionalized particles may inhibit or limit environmental transformations which influence particle aggregation, mobility, dissolution and eco-toxic potential. This paper focuses on ENM characteristics and the influence of physical, chemical and biological processes occurring in aquatic systems that are likely to impact metallic ENMs fate. A focus on silver NPs (while for comparison, reporting about other metallic ENMs as appropriate) released to aquatic systems is discussed relating to their likely fate and behaviour in this dynamic and complex environment. This paper further highlights the need for specific risk assessment approaches for metallic ENMs and puts this into context with regard to informing environmental policy and potential NP influence on environmental/human health.

Investigation of nanotoxicological effects of nanostructured hydroxyapatite to microalgae Pseudokirchneriella subcapitata

The advance of nanotechnology has enabled the development of materials with optimized properties for applications in agriculture and environment. For instance, nanotechnology-based fertilizers, such as the candidate hydroxyapatite (HAp) nanoparticles (Ca₁₀(PO₄)₆(OH)₂), can potentially increase the food production by rationally supplying phosphorous to crops, although with inferior mobility in the environment (when compared to the soluble counterparts), avoiding eutrophication. Nonetheless, the widespread consumption of nanofertilizers also raises concern about feasible deleterious effects caused by their release in the environment, which ultimately imposes risks to aquatic biota and human health. Nanoparticles characteristics such as size, shape, surface charge and chemical functionality strongly alter how they interact with the surrounding environment, leading to distinct levels of toxicity. This investigation aimed to compare the toxicity of different HAp nanoparticles, obtained by two distinct chemical routes, against algae Pseudokirchneriella subcapitata, which composes the base of the aquatic trophic chain. The as synthesized HAp nanoparticles obtained by co-precipitation and co-precipitation followed by hydrothermal method were fully characterized regarding structure and morphology. Toxicity tests against the microalgae were carried out to evaluate the growth inhibition and the morphological changes experienced by the exposition to HAp nanoparticles. The results showed that high concentrations of coprecipitated HAp samples significantly decreased cell density and caused morphological changes on the algal cells surface when compared to HAp obtained by hydrothermal method. HAp nanoparticles obtained with dispersing agent ammonium polymethacrylate (APMA) indicated negligible toxic effects for algae, due to the higher dispersion of HAp in the culture medium as well as a reduced shading effect. Therefore, HAp nanoparticles obtained by the latter route can be considered a potential source of phosphorous for agricultural crops in addition to reduce eutrophication.

Ecophysiological perspectives on engineered nanomaterial toxicity in fish and crustaceans

Engineered nanomaterials (ENMs) are incorporated into numerous industrial, clinical, food, and consumer products and a significant body of evidence is now available on their toxicity to aquatic organisms. Environmental ENM concentrations are difficult to quantify, but production and release estimates suggest wastewater treatment plant effluent levels ranging from 10^-4 to >10¹μgL^-1 for the most common formulations by production volume. Bioavailability and ENM toxicity are heavily influenced by water quality parameters and the physicochemical properties and resulting colloidal behaviour of the particular ENM formulation. ENMs generally induce only mild acute toxicity to most adult fish and crustaceans under environmentally relevant exposure scenarios; however, sensitivity may be considerably higher for certain species and life stages. In adult animals, aquatic ENM exposure often irritates respiratory and digestive epithelia and causes oxidative stress, which can be associated with cardiovascular dysfunction and the activation of immune responses. Direct interactions between ENMs (or their dissolution products) and proteins can also lead to ionoregulatory stress and/or developmental toxicity. Chronic and developmental toxicity have been noted for several common ENMs (e.g. TiO₂, Ag), however more data is necessary to accurately characterize long term ecological risks. The bioavailability of ENMs should be limited in saline waters but toxicity has been observed in marine animals, highlighting a need for more study on possible impacts in estuarine and coastal systems. Nano-enabled advancements in industrial processes like water treatment and remediation could provide significant net benefits to the environment and will likely temper the relatively modest impacts of incidental ENM release and exposure.

Cellular uptake, genotoxicity and cytotoxicity of cobalt ferrite magnetic nanoparticles in human breast cells

Magnetic nanoparticles (MNPs) have been increasingly used for many years as MRI agents and for gene delivery and hyperthermia therapy, although there have been conflicting results on their safety. In this study, cobalt ferrite magnetic nanoparticles (CoFe-MNPs) were prepared by the co-precipitation method and their surfaces were modified with silica by the sol-gel method. The particle and hydrodynamic sizes, morphology and crystal structure of the bare and silica-coated CoFe-MNPs were evaluated by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction spectroscopy (XRD) and Fourier transform infrared spectroscopy (FTIR). The size of the bare CoFe-MNPs was in the range 8-20 nm and they were homogeneously coated with 3-4 nm silica shells. The bare and silica-coated CoFe-MNPs were agglomerated at physiological pH. However, the sizes of the agglomerates were below 200 nm both in water and complete medium. The cytotoxic and genotoxic potentials of the bare and silica-coated CoFe-MNPs were evaluated in a metastatic breast cancer cell line, MDA-MB-231, as well as a noncancerous mammary epithelial cell line, MCF-10A, by using XTT cytotoxicity, single-cell gel electrophoresis (comet), and cytokinesis-blocked (CB) micronucleus (CBMN) assays. Characterization studies with TEM, inductively coupled plasma optical emission spectroscopy (ICP-OES) and Prussian blue staining indicated that the CoFe-MNPs were internalized into the cells by energy-dependent endocytosis. The highest amount of uptake was observed in the cancer cells and the uptake of the silica-coated CoFe-MNPs was higher than that of the bare ones in both cell lines. The bare CoFe-MNPs showed higher levels of both cytotoxicity and genotoxicity than the silica-coated CoFe-MNPs. Moreover, the cancer cells seemed to be more susceptible to the CoFe-MNPs' toxicity compared to the noncancerous cells. There was a concentration and time-dependent increase in DNA damage and the micronucleus (MN) frequency, which was statistically significant starting with the lowest concentration of bare CoFe-MNPs (p < 0.05), while no significance was observed below the concentration of 250 μg mL-1 for the silica-coated MNPs. Also, the extent of both DNA damage and MN frequency was much higher in the cancer cells compared to the noncancerous cells. According to our results, the silica coating ameliorated both the cytotoxicity and genotoxicity as well the internalization of the CoFe-MNPs.

Mechanisms underlying the enhancement of toxicity caused by the coincubation of zinc oxide and copper nanoparticles in a fish hepatoma cell line

Ecosystems are exposed to a wide variety of individual substances, including at the nano-scale; and the potential adverse effects of their interactions are an increasing concern. The purpose of the present study was to determine whether zinc oxide nanoparticles (ZnONPs) at a no-observed-effect concentration modulate the cytotoxicity of copper nanoparticles (CuNPs) in the fish hepatoma cell line PLHC-1 after 48 h of exposure and the contribution of the released ions to these effects. Cells were exposed to 50-nm CuNPs (0.39-25.0 µg/mL), alone or in combination with ZnONPs (25 nm or 100 nm), at 6.25 µg/mL. Cells were exposed to suspensions of NPs or to their supernatants, as well as to their combinations. The effects on cell viability were assessed through cytotoxicity assays. Changes in cell morphology and metal internalization were also evaluated. The cytotoxicity exerted by CuNPs was enhanced in the presence of nontoxic concentrations of ZnONPs. On the contrary, Zn ions protected the cell line from the CuNP toxicity, this effect being related to an increase in the intracellular levels of Zn. This increase of metal was not observed in cells exposed to both ZnONPs and CuNPs, even when they were visualized inside the cell. The results indicated that the internalization of ZnONPs, but not the Zn ions, was responsible for the enhanced toxicity of the CuNPs. Environ Toxicol Chem 2016;35:2562-2570. © 2016 SETAC.

Effects of nanomaterials on marine invertebrates

The development of nanotechnology will inevitably lead to the release of consistent amounts of nanomaterials (NMs) and nanoparticles (NPs) into marine ecosystems. Ecotoxicological studies have been carried out to identify potential biological targets of NPs, and suitable models for predicting their impact on the health of the marine environment. Recent studies in invertebrates mainly focused on NP accumulation and sub-lethal effects, rather than acute toxicity. Among marine invertebrates, bivalves represent by large the most studied group, with polychaetes and echinoderms also emerging as significant targets of NPs. However, major scientific gaps still need to be filled. In this work, factors affecting the fate of NPs in the marine environment, and their consequent uptake/accumulation/toxicity in marine invertebrates will be summarized. The results show that in different model species, NP accumulation mainly occurs in digestive tract and gills. Data on sub-lethal effects and modes of action of different types of NPs (mainly metal oxides and metal based NPs) in marine invertebrates will be reviewed, in particular on immune function, oxidative stress and embryo development. Moreover, the possibility that such effects may be influenced by NP interactions with biomolecules in both external and internal environment will be introduced. In natural environmental media, NP interactions with polysaccharides, proteins and colloids may affect their agglomeration/aggregation and consequent bioavailability. Moreover, once within the organism, NPs are known to interact with plasma proteins, forming a protein corona that can affect particle uptake and toxicity in target cells in a physiological environment. These interactions, leading to the formation of eco-bio-coronas, may be crucial in determining particle behavior and effects also in marine biota. In order to classify NPs into groups and predict the implications of their release into the marine environment, information on their intrinsic properties is clearly insufficient, and a deeper understanding of NP eco/bio-interactions is required.