Nanotoxicity and the Environment

Metal oxide nanomaterials are widely used in practical applications and represent a class of nanomaterials with the highest global annual production. Many of those, such as TiO2 and ZnO, are generally considered non-toxic due to the lack of toxicity of the bulk material. However, these materials typically exhibit toxicity to bacteria and fungi, and there have been emerging concerns about their ecotoxicity effects. The understanding of the toxicity mechanisms is incomplete, with different studies often reporting contradictory results. The relationship between the material properties and toxicity appears to be complex and diifficult to understand, which is partly due to incomplete characterization of the nanomaterial, and possibly due to experimental artefacts in the characterization of the nanomaterial and/or its interactions with living organisms. This review discusses the comprehensive characterization of metal oxide nanomaterials and the mechanisms of their toxicity.

Corn fibers and luffa peels were evaluated for removing toxic heavy metal ions and dissolved organic dyes from water. Fresh peels were pretreated to remove all soluble components before using them for extraction studies. Presence of eOH and eCO 2 H functional groups on the surface of the peels and rough morphologies were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy investigations, respectively. Corn fibers and luffa peels showed maximum extraction effi-ciencies within the pH range of 4e10 and adsorption reached a steady state within 2e3 h. Prewashed corn fibers and luffa peals extracted 159 mg g À1 and 90 mg g À1 of alcian blue, 70 mg g À1 and 124 mg g À1 of methylene blue, 50 mg g À1 and 108 mg g À1 of neutral red as well as 35 mg g À1 and 40 mg g À1 of coomassie brilliant blue from water, respectively. Both materials did not show significant extraction affinity towards heavy metal ions such as Pb 2þ (1 mg g À1), Ni 2þ (4 mg g À1 for corn fiber and 12 mg g À1 for luffa peels), and chromate (3 mg g À1 for corn fibers and 6 mg g À1 for luffa peels) ions from water. The Langmuir and Freundlich isotherms were used to understand the adsorption process on the surface of the adsorbents. Langmuir isotherm model yielded the best fit for the data obtained in the study, indicating a monolayer adsorption of pollutants on the adsorbent surface. Both adsorbents can be regenerated at acidic pH and could be reused for up to five cycles without significant loss of efficiency. Our experimental results suggest that both natural materials are effective towards removing dissolved dyes from water.

Abstract: Some authors use the term “nanosensor” for biomolecules in nano molar concentrations
acting as signals for living cells. In our review we emphasize on microbial sensors for detecting pathogens and on the “hardware” – the type of nanostructures used as a pad of bio sensing element. The main object is different type of nano-structured material used in the sensing process – non functionalized metal nanoparticles, metal oxides forming thin films and functionalized sensors as antibody-coated and aptamer-coated nanostructures and thin films.
The latter have shown high selectivity and sensitivity and appear to be promising for future applications in medicine and
environmental testing. Our investigation proved the sensitivity of thin zinc oxide films to bacterial quantity of Gracilicutes and Firmicutes bacteria. The observed sensitivity was a single cell in a drop of water, but the change of potential to Pseudomonas cells  was almost ten times higher than to Bacillus. It could be due not only to the bacterial type of cell wall but also to the type of dopant and the crystal structure of the ZnO thin film. Recent patents based on nanostructures for detection of clinically important pathogens are discussed.

Silver nanoparticles are well known potent antimicrobial agents. Although significant progresses have been achieved on the elucidation of antimicrobial mechanism of silver nanoparticles, the exact mechanism of action is still not completely known. This overview incorporates a retrospective of previous reviews published and recent original contributions on the progress of research on antimicrobial mechanisms of silver nanoparticles. The main topics discussed include release of silver nanoparticles and silver ions, cell membrane damage, DNA interaction, free radical generation, bacterial resistance and the relationship of resistance to silver ions versus resistance to silver nanoparticles. The focus of the overview is to summarize the current knowledge in the field of antibacterial activity of silver nanoparticles. The possibility that pathogenic microbes may develop resistance to silver nanoparticles is also discussed.

Classic chemotherapy has little or no specificity for cancer cells, normally resulting in low accumulation at the tumor region (inefficacy), and in severe side effects (toxicity). This challenge has resulted in the development of several delivery strategies for chemotherapy agents to improve their concentration at the tumor site, simultaneously increasing their anticancer efficacy, while reducing the associated adverse systemic effects. In this work, the potential of drug delivery strategies involving the use of nanocarriers for controlling the biodistribution of antitumor drugs is deeply revised: passive targeting (through the enhanced permeability and retention effect, EPR effect) and active targeting (including stimuli-sensitive carriers and ligand-mediated delivery). Special attention will be also focussed on the recent approaches for overcoming multi-drug resistance. Finally, a general view of the problem of “nanotoxicity” in cancer treatment is also given.

Hemoglobin has a very strong affinity with oxygen and thus is a good catalyst to carry oxygen for many oxidation reactions. Many researchers have explored this property of hemoglobin to develop sensors for the detection of nitrite and peroxide, that are important in biomedical and environmental monitoring. We have previously reported the development of biosensors that can detect nitrite and peroxide with a lower detecting limit below 1x10 -12 M, that were among the best detectors at the time. With a similar sensor platform, we have now developed a biosensor that can detect the oxidation reaction orders of magnitude better than the previous sensors. The sensor comprises layers of biocomposite made up of a polymer, nanogold particles, and a complex protein on the surface of an electrode. The performance of this electrode biosensor is compared with the previously developed sensors, the durability and other factors that can affect the performance and fabrication of this biosensor are discussed.

Over the last decade, engineered nanomaterials (NMs) brought a revolutionary development in many sectors of human life including electronics, paints, textiles, food, agriculture, and health care. However, the exponential growth in the number of NMs applications resulted in uncertainties regarding their environmental impacts. Currently, the common approach for assessing the toxicity of NMs such as, carbon-(fullerenes, single-and multi-walled carbon nanotubes), mineral-(gold and silver nanoparticles, cerium and zinc oxide, silicon and titanium dioxide), and organic-based NMs (dendrimers) includes standard guidelines applied to all chemical compounds. Nevertheless, NMs differ from traditional materials as their physicochemical and surface properties influence the toxic rather than their composition alone. Considering such NMs specificities, adaptations in some methods are necessary to ensure that environmental and human health risks are accurately investigated. In this context, the focus of this mini-review is to summarize the current knowledge in nanotoxicology regarding relevant organisms and experimental assays for assessing the terrestrial toxicity of NMs.

Atrazine is one of the most used herbicides and has been associated with persistent surface and groundwater contamination, and novel formulations derived from nanotechnology can be a potential solution. We used poly(ε-caprolactone) nanoencapsulation of atrazine (NC+ATZ) to develop a highly effective herbicidal formulation. Detailed structural study of interaction between the formulation and Brassica juncea plants was carried out with evaluation of the foliar uptake of nanoatrazine and structural alterations induced in the leaves. Following postemergent treatment, NC+ATZ adhered to the leaf and penetrated mesophyll tissue mainly through the hydathode regions. NC+ATZ was transported directly through the vascular tissue of the leaves and into the cells where it degraded the chloroplasts resulting in herbicidal activity. Nanocarrier systems, such as the one used in this study, have great potential for agricultural applications in terms of maintenance of herbicidal activity at low concentrations and a substantial increase in the herbicidal efficacy.

Gold nanomaterials (Au NMs) have been explored for a wide range of applications in catalysis and medicine. Here we report the shape sensitive toxicity of gold nanoplates (Au nanoplates) in breast cancer cell line, MCF7. Au nanoplates induced a dose-and shape-dependent toxicity to cancer cells. Oxidative stress induced by Au nanoplates is believed to be the trigger for the DNA, which resulted in cell apoptosis. In summary, the results from our study demonstrate that morphology appears to play a significant role in mediating the cellular responses and Au triangles nanoplates showed the highest toxicity to the cells. Such findings may be able to shine more light on the shape-dependent interaction between Au NMs and living organisms.

Nanostructured materials (NSMs) of silver (Ag@TiO 2) and copper (TiO 2-Cu 2+) doped titanium dioxide were synthesized, fully characterized, and evaluated for their antimicrobial efficiency and effects on Arabidopsis thaliana. The NSMs were prepared using an environmentally benign route. The physicochemical properties of the materials were determined with analytical techniques. These materials are active under visible light, exhibit a small size (10–12 nm), are crystalline (anatase), and liberate metal ions (Ag + and Cu 2+) in solution. Microbicide activity was observed in E. coli C600 and S. cerevisiae W303 strains treated with several concentrations of Ag@TiO 2 and TiO 2-Cu 2+ , radiated and nonradiated, and after different times. Higher inactivation was achieved with Ag@TiO 2 in E. coli, with value of log inactivation of 2.2 with 0.5 mg/mL after 4 h, than in S. cerevisiae, with a log inactivation of 2.6 with 10 mg/mL after 24 h. The impact of these NSMs in plants was evaluated in Arabidopsis thaliana Col-0 strain exposed to such materials at different conditions and concentrations, and physical and biochemical effects were analyzed. Seeds exposed to NSMs did not show effects on germination and growth. However, seedlings treated with these materials modified their growth and their total chlorophyll content.

The broad spectrum applications of CoFe2O4 NPs have attracted much interest in medicine, environment and industry, resulting in exceedingly higher exposures to humans and environmental systems
in succeeding days. Their health effects and potential biological impacts need to be determined for risk
assessment. Zebrafish (Danio rerio) embryos were exposed to environmentally relevant doses of nanoCoFe2O4 (mean diameter of 40 nm) with a concentration range of 10–500 M for 96 h. Acute toxic end
points were evaluated by survival rate, malformation, hatching delay, heart dysfunction and tail flexure
of larvae. Dose and time dependent developmental toxicity with severe cardiac edema, down regulation
of metabolism, hatching delay and tail/spinal cord flexure and apoptosis was observed. The biochemical
changes were evaluated by ROS, Catalase (CAT), Lipid peroxidation (LPO), Acid phophatase (AP) and Glutatione s- transferase (GST). An Agglomeration of NPs and dissolution of ions induces severe mechanical
damage to membranes and oxidative stress. Severe apoptosis of cells in the head, heart and tail region
with inhibition of catalase confirms ROS induced acute toxicity with increasing concentration. Increased
activity of GST and AP at lower concentrations of CoFe2O4 NPs demonstrates the severe oxidative stress.
Circular dichroism (CD) spectra indicated the weak interactions of NPs with BSA and slight changes
in -helix structure. In addition, CoFe2O4 NPs at lower concentrations do not show any considerable
interference with assay components and analytical instruments. The results are possible elucidation of
pathways of toxicity induced by these particles, as well as contributing in defining the protocols for risk
assessment of these nanoparticles.

the usefulness of matrix-assisted laser desorption/ioniza- tion (MALDI) mass spectrometry imaging (MSI) as a new imaging method for detecting the temporal distribution of nanomaterials throughout the brain.
Conclusions: rGO was able to be detected and monitored in the brain over time provided by a novel application for MALDI-MSI and could be a useful tool for treating a variety of brain disorders that are normally unresponsive to conventional treatment because of BBB impermeability.
Keywords: Blood–brain barrier, Paracellular pathway, Nanomaterials, MALDI-MSI

The majority of the current production, use, and disposal of engineered nanomaterials
(ENMs) occur in terrestrial environments, and consequently terrestrial ecosystems are and will increasingly be some of the largest receptors of ENMs at all stages of their life cycles. In particular, soil is predicted to be one of the major receptors of ENMs due to ENM-contaminated biosolid fertilizer and nanopesticide application to agricultural fields, runoff from landfills or ENM-bearing paints, or atmospheric deposition. Both agricultural and natural systems are at risk to ENM contamination via these release scenarios, which makes it necessary to understand the interactions between ENMs, soils, and soil organisms such as plants in order to predict their impacts in real-world scenarios.
Gravity-driven vertical transport of TiO2, CeO2, and Cu(OH)2 engineered
nanomaterials (ENMs) and their effects on soil pH and nutrient release were measured in three unsaturated soils. ENM transport was found to be highly limited in natural soils collected from farmland and grasslands, with the majority of particles being retained in the upper 0-3 cm of the soil profile, while greater transport depth was seen in a commercial potting soil. Physical straining appeared to be the primary mechanism of retention in natural soils as ENMs immediately formed micron-scale aggregates, which was exacerbated by coating particles with Suwannee River natural organic matter (NOM).
Changes in soil pH were observed in natural soils contaminated with ENMs that
were largely independent of ENM type and concentration. These changes may have been due to enhanced release of naturally present pH-altering ions (Mg2+, H+) in the soil, likely via substitution processes. This suggests ENMs will likely be highly retained near source zones in soil and may impact local communities sensitive to changes in pH or nutrient availability.
Few studies have investigated the influence of environmental conditions on ENM
uptake and toxicity, particularly throughout the entire plant life cycle. Here, soil-grown
plants (Clarkia unguiculata, Raphanus sativus, and Triticum aestivum) were exposed until maturity to TiO2, CeO2, or Cu(OH)2 ENMs under different illumination intensities, in different soils, and with different nutrient levels. Fluorescence and gas exchange
measurements were recorded throughout growth and tissue samples from mature plants were analyzed for metal content. ENM uptake was observed in all plant species, but was seen to vary significantly with ENM type, light intensity, nutrient levels, and soil type. Light intensity in particular was found to be important in controlling uptake, likely as a result of plants increasing or decreasing transpiration in response to light.
Significant impacts on plant transpiration, photosynthetic rate, CO2 assimilation
efficiency, water use efficiency, and other parameters related to physiological fitness were seen. The impacts were highly dependent on environmental conditions as well as ENM and soil type. Notably, many of these effects were found to be mitigated in soils with limited ENM mobility due to decreased uptake. These results show that abiotic conditions play an important role in mediating the uptake and physiological impacts of ENMs in terrestrial plants.

Poly(epsilon-caprolactone) (PCL) nanocapsules have been used as a carrier system for the herbicide atrazine, which is commonly applied to maize. We demonstrated previously that these atrazine containing polymeric nanocapsules were 10-fold more effective in the control of mustard plants (a target species), as compared to a commercial atrazine formulation. Since atrazine can have adverse effects on non-target crops, here we analyzed the effect of encapsulated atrazine on growth, physiological and oxidative stress parameters of soil-grown maize plants (Zea mays L.). One day after the post-emergence treatment with PCL nanocapsules containing atrazine (1 mg mL−1 ), maize plants presented 15 and 21% decreases in maximum quantum yield of photosystem II (PSII) and in net CO2 assimilation rate, respectively, as compared to water-sprayed plants. The same treatment led to a 1.8-fold increase in leaf lipid peroxidation in comparison with control plants. However, all of these parameters were unaffected 4 and 8 days after the application of encapsulated atrazine. These results suggested that the negative effects of atrazine were transient, probably due to the ability of maize plants to detoxify the herbicide. When encapsulated atrazine was applied at a 10-fold lower concentration (0.1 mg mL−1), a dosage that is still effective for weed control, no effects were detected even shortly after application. Regardless of the herbicide concentration, neither pre- nor post-emergence treatment with the PCL nanocapsules carrying atrazine resulted in the development of any macroscopic symptoms in maize leaves, and there were no impacts on shoot growth. Additionally, no effects were observed when plants were sprayed with PCL nanocapsules without atrazine. Overall, these results suggested that the use of PCL nanocapsules containing atrazine did not lead to persistent side effects in maize plants, and that the technique could offer a safe tool for weed control without affecting crop growth.

Poly(epsilon-caprolactone) (PCL) nanocapsules have been recently developed as a modi- fied release system for atrazine, an herbicide that can have harmful effects in the environ- ment. Here, the post-emergence herbicidal activity of PCL nanocapsules containing atrazine was evaluated using mustard (Brassica juncea) as target plant species model. Characterization of atrazine-loaded PCL nanocapsules by nanoparticle tracking analysis indicated a concentration of 7.5 x 1012 particles mL-1 and an average size distribution of 240.7 nm. The treatment of mustard plants with nanocapsules carrying atrazine at 1 mg mL-1 resulted in a decrease of net photosynthesis and PSII maximum quantum yield, and an increase of leaf lipid peroxidation, leading to shoot growth inhibition and the development of severe symptoms. Time course analysis until 72 h after treatments showed that nanoen- capsulation of atrazine enhanced the herbicidal activity in comparison with a commercial atrazine formulation. In contrast to the commercial formulation, ten-fold dilution of the atra- zine-containing nanocapsules did not compromise the herbicidal activity. No effects were observed when plants were treated with nanocapsules without herbicide compared to con- trol leaves sprayed with water. Overall, these results demonstrated that atrazine-containing PCL nanocapsules provide very effective post-emergence herbicidal activity. More impor- tantly, the use of nanoencapsulated atrazine enables the application of lower dosages of the herbicide, without any loss of efficiency, which could provide environmental benefits.

Bacterial adhesion onto inorganic/nanoengineered surfaces is a key issue in biotechnology and medicine, because it is one of the first necessary steps to determine a general pathogenic event. Understanding the molecular mechanisms of bacteria-surface interaction represents a milestone for planning a new generation of devices with unanimously certified antibacterial characteristics. Here, we show how highly controlled nanostructured substrates impact the bacterial behavior in terms of morphological, genomic, and proteomic response. We observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM) that type-1 fimbriae typically disappear in Escherichia coli adherent onto nanostructured substrates, as opposed to bacteria onto reference glass or flat gold surfaces. A genetic variation of the fimbrial operon regulation was consistently identified by real time qPCR in bacteria interacting with the nanorough substrates. To gain a deeper insight into the molecular basis of the interaction mechanisms, we explored the entire proteomic profile of E. coli by 2D-DIGE, finding significant changes in the bacteria adherent onto the nanorough substrates, such as regulations of proteins involved in stress processes and defense mechanisms. We thus demonstrated that a pure physical stimulus, that is, a nanoscale variation of surface topography, may play per se a significant role in determining the morphological, genetic, and proteomic profile of bacteria. These data suggest that in depth investigations of the molecular processes of microorganisms adhering to surfaces are of great importance for the design of innovative biomaterials with active biological functionalities.

Considering the prevalence of emerging nanotechnology, predicting the environmental impact of nanomaterials has great importance. The aim of this study was to investigate the possible accumulation and histological damage resulting from the exposure of fish to silver nanoparticles (AgNPs). Hence, rainbow trout (Oncorhynchus mykiss) were exposed for 21 days to sublethal concentrations of either colloidal or powdered forms of silver nanoparticles (cAgNPs or pAgNPs, respectively); the resulting histological changes (in gills, intestines, liver, and kidneys) and bioaccumulation (in gills, intestines, liver, and white muscles) were examined on days 11 and 21. In the case of cAgNPs, the highest concentrations of silver were observed in the liver, gills, and intestines. Meanwhile, in the case of pAgNPs, the highest concentrations of silver were observed in the intestines, liver, gills, and muscles. The greatest histopathological impacts were observed in the gills (mostly proliferation and inflammation), intestines (mostly necrosis and inflammation), and liver (mostly pigmentation). Thus, when taken together, the current findings indicate that both forms of AgNPs had a chronic effect on the rainbow trout (as a model aquatic organism); therefore, preventing the entry of these nanomaterials into the aquatic environment would seem to be essential.

Toxicity of ZnO nanoparticles (NPs) are often related to the release of Zn 2+ ions due to their dissolution. Studies also suggest that the toxicity of ZnO NPs cannot be solely explained by the release of Zn 2+ ions; however, there is a lack of direct evidence of ZnO particulate effects. This study compared the acute toxicity of ZnO NPs and ZnSO 4 following intranasal exposure using a combination of metallomics and metabolomics approaches. Significant accumulation of Zn in the liver was only found in the ZnO NP treatment, with 29% of the newly accumulated Zn in the form of ZnO as revealed by X-ray fine structure spectroscopy (XAFS). This is the first direct evidence suggesting the persistence of ZnO NPs in liver upon intranasal exposure. Although both ZnO NPs and ZnSO 4 altered the metabolite profiles, with some overlaps and considerable specificity, of both liver and plasma samples, more and distinct metabolites in the liver and opposite effects in the plasma were altered by ZnO NPs compared with ZnSO 4 , consistent with no accumulation of Zn detected in liver from ZnSO 4. Specifically, a large number of antioxidant-related compounds and energetic substrates were exclusively elevated in the liver of ZnO NP-treated animals. These findings provided direct evidence that persistence of ZnO NPs induced particle-specific effects on the antioxidant systems and energy metabolism pathways.

Bacterial adhesion onto abiotic surfaces is an important issue in biology and medicine since understanding the bases of such interaction represents a crucial aspect in the design of safe implant devices with intrinsic antibacterial characteristics. In this framework, we investigated the effects of nanostructured metal substrates on Escherichia coli adhesion and adaptation in order to understand the bio-molecular dynamics ruling the interactions at the interface. In particular, we show how highly controlled nanostructured gold substrates impact the bacterial behavior in terms of morphological changes and lead to modifications in the expression profile of several genes, which are crucially involved in the stress response and fimbrial synthesis. These results mainly demonstrate that E. coli cells are able to sense even slight changes in surface nanotopography and to actively respond by activating stress-related pathways. At the same time, our findings highlight the possibility of designing nanoengineered substrates able to trigger specific bio-molecular effects, thus opening the perspective of smartly tuning bacterial behavior by biomaterial design.

Development in nanotechnology field has generated both positive and negative responses from gov-ernments, scientists and social media throughout the world. Metal-oxide nanoparticles are class of nanoparticles with wide range of properties and application in industries due to their ability to bind with molecules and catalyze chemical reaction at nano scale. Industries producing and using nanopar-ticles are releasing these particles in their waste water. We assumed that when such forms of nanopar-ticles enter into the environment they could release their metal in free radical forms which can be toxic to microorganisms. Inherent microbes are key determinants of soil quality and functioning of various nutrient cycles in ecosystem. In present study investigation of influences of ZnO and TiO 2 nanopar-ticles was studied on normal soil inhabiting bacteria including plant growth promoting rhizobacteria as well as important polymer decomposers such as Bacillus subtilis, E. coli, P. putida, B...

Our interest in ecologic problems started with endocrine disruptors and continued later in the field of nanotoxicology . However, there is some overlap in classification of various types of particulate matter, including nanoparticles. In fact, environmental toxicology differentiates coarse, fine and ultrafine particles with aerodynamic diameter less than 10, 2.5 and 0.1 µm respectively, whereas nanotoxicology describes the effects of nanoparticles with dimensions less than 100 nm, i.e. coinciding with ultrafine particles. Therefore, nanotoxicologists add "engineered" or "manufactured" to the term of nanoparticles, in order to delineate better their object of research.

Bacterial adhesion onto inorganic/nanoengineered surfaces is a key issue in biotechnology and medicine, because it is one of the first necessary steps to determine a general pathogenic event. Understanding the molecular mechanisms of bacteria-surface interaction represents a milestone for planning a new generation of devices with unanimously certified antibacterial characteristics. Here, we show how highly controlled nanostructured substrates impact the bacterial behavior in terms of morphological, genomic, and proteomic response. We observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM) that type-1 fimbriae typically disappear in Escherichia coli adherent onto nanostructured substrates, as opposed to bacteria onto reference glass or flat gold surfaces. A genetic variation of the fimbrial operon regulation was consistently identified by real time qPCR in bacteria interacting with the nanorough substrates. To gain a deeper insight into the molecular basis of the interaction mechanisms, we explored the entire proteomic profile of E. coli by 2D-DIGE, finding significant changes in the bacteria adherent onto the nanorough substrates, such as regulations of proteins involved in stress processes and defense mechanisms. We thus demonstrated that a pure physical stimulus, that is, a nanoscale variation of surface topography, may play per se a significant role in determining the morphological, genetic, and proteomic profile of bacteria. These data suggest that in depth investigations of the molecular processes of microorganisms adhering to surfaces are of great importance for the design of innovative biomaterials with active biological functionalities.