Manufactured Nanoparticles Research Articles

Physiological and molecular effects of contaminants of emerging concerns of micro and nano-size in aquatic metazoans: overview and current gaps in Antarctic species.

Although Antarctica is the most isolated continent on Earth, its remote location does not protect it from the impacts of human activities. Antarctic metazoans such as filter-feeding invertebrates are a crucial component of the Antarctic benthos. They play a key role in the benthic-pelagic carbon flux in coastal areas by filtering particles and planktonic organisms from the sediment-water interface. Due to their peculiar ecological niche, these organisms can be considered a wasp-waist in the ecosystem, making them highly sensitive to marine pollution. Recently, anthropogenic particles such as micro-nanoplastics and manufactured nanoparticles (MNP) have been classified as contaminants of emerging concern (CEC) due to their small size range, which also overlaps with the preferred particle size ingested by aquatic metazoans. Indeed, it has been demonstrated that some species such as Antarctic krill can ingest, transform, and release MNPs, making them newly bioavailable for other Antarctic filter-feeding organisms. Similarly, the production and use of anthropogenic MNP are rapidly increasing, leading to a growing presence of materials, such as nano-sized metal-oxides, in the environment. For these reasons, it is important to provide evidence of the adverse effects of such emerging contaminants at sub-lethal concentrations in environmental risk assessments. These contaminants may cause cascade effects with consequences not only on individuals but also at the community and ecosystem levels. In this review, we discuss the state-of-the-art knowledge on the physiological and molecular effects of anthropogenic MNP in Antarctic aquatic metazoans. We further highlight the importance of identifying early biomarkers using sessile metazoans as sentinels of environmental health.

Toxicogenomic responses of Caenorhabditis elegans to pristine and transformed zinc oxide nanoparticles

Manufactured nanoparticles (MNPs) undergo transformation immediately after they enter wastewater treatment streams and during their partitioning to sewage sludge, which is applied to agricultural soils in form of biosolids. We examined toxicogenomic responses of the model nematode Caenorhabditis elegans to pristine and transformed ZnO-MNPs (phosphatized pZnO- and sulfidized sZnO-MNPs). To account for the toxicity due to dissolved Zn, a ZnSO4 treatment was included. Transformation of ZnO-MNPs reduced their toxicity by nearly ten-fold, while there was almost no difference in the toxicity of pristine ZnO-MNPs and ZnSO4. This combined with the fact that far more dissolved Zn was released from ZnO- compared to pZnO- or sZnO-MNPs, suggests that dissolution of pristine ZnO-MNPs is one of the main drivers of their toxicity. Transcriptomic responses at the EC30 for reproduction resulted in a total of 1161 differentially expressed genes. Fifty percent of the genes differentially expressed in the ZnSO4 treatment, including the three metal responsive genes (mtl-1, mtl-2 and numr-1), were shared among all treatments, suggesting that responses to all forms of Zn could be partially attributed to dissolved Zn. However, the toxicity and transcriptomic responses in all MNP treatments cannot be fully explained by dissolved Zn. Two of the biological pathways identified, one essential for protein biosynthesis (Aminoacyl-tRNA biosynthesis) and another associated with detoxification (ABC transporters), were shared among pristine and one or both transformed ZnO-MNPs, but not ZnSO4. When comparing pristine and transformed ZnO-MNPs, 66% and 40% of genes were shared between ZnO-MNPs and sZnO-MNPs or pZnO-MNPs, respectively. This suggests greater similarity in transcriptomic responses between ZnO-MNPs and sZnO-MNPs, while toxicity mechanisms are more distinct for pZnO-MNPs, where 13 unique biological pathways were identified. Based on these pathways, the toxicity of pZnO-MNPs is likely to be associated with their adverse effect on digestion and metabolism.

Investigation of cloud point extraction for the analysis of metallic nanoparticles in a soil matrix.

The characterization of manufactured nanoparticles (MNPs) in environmental samples is necessary to assess their behavior, fate and potential toxicity. Several techniques are available, but the limit of detection (LOD) is often too high for environmentally relevant concentrations. Therefore, pre-concentration of MNPs is an important component in the sample preparation step, in order to apply analytical tools with a LOD higher than the ng kg-1 level. The objective of this study was to explore cloud point extraction (CPE) as a viable method to pre-concentrate gold nanoparticles (AuNPs), as a model MNP, spiked into a soil extract matrix. To that end, different extraction conditions and surface coatings were evaluated in a simple matrix. The CPE method was then applied to soil extract samples spiked with AuNPs. Total gold, determined by inductively coupled plasma mass spectrometry (ICP-MS) following acid digestion, yielded a recovery greater than 90 %. The first known application of single particle ICP-MS and asymmetric flow field-flow fractionation to evaluate the preservation of the AuNP physical state following CPE extraction is demonstrated.

Mouse Mesothelium-Derived Cell Lines:Models to Assess Cytotoxic Effects of Novel Nanomaterials <I>in vitro</I> and to Ultimately Investigating Carcinogenesis <I>in vivo</I>

Novel nanomaterials are continuously produced, but still little is known about their potential toxic and carcinogenic effects. In contrast, crocidolite is one of the best-characterized asbestos types known to induce nanotoxicity and to transform mesothelial cells resulting in malignant mesothelioma. Only in few reports mesothelial or mesothelioma-derived cells were used to investigate nanotoxicity and/or carcinogenicity. Even less studies were carried out with mouse-derived cell lines allowing to investigating nanotoxicity in vivo. Immortalized mesothelial cells from wildtype (iMeso-WT1), from NF2+/- heterozygous (iMeso-NF3) mice and the NF2+/- mouse-derived mesothelioma cell line RN5 were used to compare acute cytotoxicity between novel silica-based manufactured nanoparticles (MNP) and crocidolite. All cell lines were sensitive to crocidolite-induced cytotoxicity, but rather resistant to the spherical MNP, with iMeso-NF3 being the most sensitive and RN5 being the least sensitive cells. Chronic exposure (1 month) of iMeso-NF3 cells to a sub-lethal dose of crocidolite resulted in increased acute resistance to crocidolite. Yet, asbestos-resistant iMeso-NF3 cells didn't induce tumors after intraperitoneal injection, while RN5 cell injection resulted in macroscopic tumors after 5 weeks. Thus, mouse mesothelium-derived cell lines appear well suited to study potential hazardous health effects of MNP.

Distinct transcriptomic responses of Caenorhabditis elegans to pristine and sulfidized silver nanoparticles

Manufactured nanoparticles (MNP) rapidly undergo aging processes once released from products. Silver sulfide (Ag2S) is the major transformation product formed during the wastewater treatment process for Ag-MNP. We examined toxicogenomic responses of pristine Ag-MNP, sulfidized Ag-MNP (sAg-MNP), and AgNO3 to a model soil organism, Caenorhabditis elegans. Transcriptomic profiling of nematodes which were exposed at the EC30 for reproduction for AgNO3, Ag-MNP, and sAg-MNP resulted in 571 differentially expressed genes. We independently verified expression of 4 genes (numr-1, rol-8, col-158, and grl-20) using qRT-PCR. Only 11% of differentially expressed genes were common among the three treatments. Gene ontology enrichment analysis also revealed that Ag-MNP and sAg-MNP had distinct toxicity mechanisms and did not share any of the biological processes. The processes most affected by Ag-MNP relate to metabolism, while those processes most affected by sAg-MNP relate to molting and the cuticle, and the most impacted processes for AgNO3 exposed nematodes was stress related. Additionally, as observed from qRT-PCR and mutant experiments, the responses to sAg-MNP were distinct from AgNO3 while some of the effects of pristine MNP were similar to AgNO3, suggesting that effects from Ag-MNP is partially due to dissolved silver ions.

Nanoparticle pollution and associated increasing potential risks on environment and human health: a case study of China.

The aims of this study are (1) to discuss the mechanism of nanoparticle lifecycle and estimate the impacts of its associated pollution on environment and human health; and (2) to provide recommendation to policy makers on how to leverage nanopollution and human health along with the rapid development of economics in China. Manufactured nanoparticles (MNPs) could either directly or indirectly impair human health and the environment. Exposures to MNP include many ways, such as via inhalation, ingestion, direct contact, or the use of consumer products over the lifecycle of the product. In China, the number of people exposed to MNP has been increasing year by year. To better provide medical care to people exposed to MNP, the Chinese government has established many disease control and prevention centers over China. However, the existing facilities and resources for controlling MNP are still not enough considering the number of people impacted by MNP and the number of ordinary workers in the MNP related industry applying for their occupational identification through the Center for Disease Control and Prevention. China should assess the apparent risk environment and human health being exposed to MNP and develop action plans to reduce the possibility of direct contacts between human beings and the emerging nanomaterials. In addition, we suggest more comprehensive studies on the MNP behavior and the development of quantitative approaches to measure MNP transport, and persistence should be carried out.

Analysis of soil bacteria susceptibility to manufactured nanoparticles via data visualization.

The impact of ZnO and TiO2 manufactured nanoparticles (MNPs) on soil bacterial communities for different exposure periods and MNP doses was explored via data visualization techniques. Interrelationships between MNP treatments and responses of bacterial taxa were illustrated by bipartite graphs, allowing fast identification of important soil bacterial taxa that are susceptible to MNPs. Contribution biplots with subcompositional coherence property were generated via log-ratio analysis (LRA), which jointly display the treatment distribution and the variance (contribution) of bacterial taxa. The LRA contribution biplots and nonmetric multi-dimensional scaling (NMDS) of the dataset, along with hierarchical clustering, demonstrated that high doses of ZnO and TiO2 MNPs caused significant compositional changes in soil bacterial communities. The suitability of family level for MNP taxonomic impact assessment was demonstrated by both the LRA biplots and simplified NMDSs with quantification provided by the distance correlation between MNP impacts summarized at different taxonomic levels. The present study demonstrates that visual exploration could potentially assist in knowledge discovery and interpretation of data on soil bacterial communities exposed to MNPs and thus evaluate the potential for environmental impacts.

Stability of Fe-oxide nanoparticles coated with natural organic matter under relevant environmental conditions.

Manufactured nanoparticles (MNPs) are increasingly released into the environment and thus research on their fate and behaviour in complex environmental samples is urgently needed. The fate of MNPs in the aquatic environment will mainly depend on the physico-chemical characteristics of the medium. The presence and concentration of natural organic matter (NOM) will play a significant role on the stability of MNPs by either decreasing or exacerbating the aggregation phenomenon. In this study, we firstly investigated the effect of NOM concentration on the aggregation behaviour of manufactured Fe-oxide nanoparticles. Then, the stability of the coated nanoparticles was assessed under relevant environmental conditions. Flow field-flow fractionation, an emerging method which is gaining popularity in the field of nanotechnology, has been employed and results have been compared to another size-measurement technique to provide increased confidence in the outcomes. Results showed enhanced stability when the nanoparticles are coated with NOM, which was due to electrosteric stabilisation. However, the presence of divalent cations, even at low concentration (i.e. less than 1 mM) was found to induce aggregation of NOM-coated nanoparticles via bridging mechanisms between NOM and Ca(2+).

Modeling Population Exposures to Silver Nanoparticles Present in Consumer Products.

Exposures of the general population to manufactured nanoparticles (MNPs) are expected to keep rising due to increasing use of MNPs in common consumer products (PEN 2014). The present study focuses on characterizing ambient and indoor population exposures to silver MNPs (nAg). For situations where detailed, case-specific exposure-related data are not available, as in the present study, a novel tiered modeling system, Prioritization/Ranking of Toxic Exposures with GIS (Geographic Information System) Extension (PRoTEGE), has been developed: it employs a product Life Cycle Analysis (LCA) approach coupled with basic human Life Stage Analysis (LSA) to characterize potential exposures to chemicals of current and emerging concern. The PRoTEGE system has been implemented for ambient and indoor environments, utilizing available MNP production, usage, and properties databases, along with laboratory measurements of potential personal exposures from consumer spray products containing nAg. Modeling of environmental and microenvironmental levels of MNPs employs Probabilistic Material Flow Analysis combined with product LCA to account for releases during manufacturing, transport, usage, disposal, etc. Human exposure and dose characterization further employs screening Microenvironmental Modeling and Intake Fraction methods combined with LSA for potentially exposed populations, to assess differences associated with gender, age, and demographics. Population distributions of intakes, estimated using the PRoTEGE framework, are consistent with published individual-based intake estimates, demonstrating that PRoTEGE is capable of capturing realistic exposure scenarios for the US population. Distributions of intakes are also used to calculate biologically-relevant population distributions of uptakes and target tissue doses through human airway dosimetry modeling that takes into account product MNP size distributions and age-relevant physiological parameters.

Species-specific toxicity of ceria nanoparticles to Lactuca plants

Species-specific differences in the toxicity of manufactured nanoparticles (MNPs) have been reported, but the underlying mechanisms are unknown. We previously found that CeO2 NPs inhibited root elongation of head lettuce, whereas no toxic effect was observed on other plants (such as wheat, cucumber and radish). In this study, interactions between Lactuca plants and three types of CeO2 NPs (lab-synthesized 7 and 25 nm CeO2 NPs, and a commercial CeO2 NPs) were investigated. It was found that CeO2 NPs were toxic to three kinds of Lactuca genus plants and different CeO2 NPs showed different degrees of toxicity. The results of X-ray absorption near edge fine structure indicate that small parts of CeO2 NPs were transformed from Ce(IV) to Ce(III) in roots of the plants that were treated with CeO2 NPs during the seed germination stage. But the high sensitivity of Lactuca plants to the released Ce3+ ions caused the species-specific phytotoxicity of CeO2 NPs. Differences in sizes and zeta potentials among three types of CeO2 NPs resulted in their different degrees of biotransformation which accounted for the discrepancy in the toxicity to Lactuca plants. This study is among the few, and may indeed the first, that addresses the relation between the physicochemical properties of nanoparticles and its species-specific phytotoxicity.

Applications and implications of manufactured nanoparticles in soils: a review

The environmental application and risk assessment of manufactured nanoparticles (MNPs) in soil greatly depend on our understanding of the interactions between MNPs and soil components. Because of the complexity of the soil system and the very early stage of MNP research in soil, our understanding of MNP behaviour in this system is very limited. This review summarizes the progress of research on MNPs and their implications for soils. Manufactured nanoparticles are applied deliberately for soil remediation and are also released unintentionally through various other pathways to soil. Their colloidal behaviour in the soil system is discussed by analysing the effect of dissolved organic matter, light irradiation, water chemistry conditions and biological processes. The methods currently used for modelling MNP leaching and transport are summarized and several requirements for model improvement are proposed. The current topics regarding the environmental risks of MNPs (such as identifying the toxicity of MNPs and their dissolved ions, evidence that MNPs may be taken up by soil organisms or the risks of other pollutants as affected by the presence of MNPs) are described. Future research directions are discussed and proposed.

Inhaled nanoparticles and lung cancer - what we can learn from conventional particle toxicology

Manufactured nanoparticles (MNP) represent a growth area in industry where their interesting and useful properties bestow advantage over conventional particles for many purposes. This review specifically addresses the potential for lung cancer in those who might be exposed to airborne MNP. There is no strong evidence that MNP are carcinogenic and MNP come in a wide spectrum of materials, sizes, shapes and compositions and it is likely that the hazard will vary across different MNP types dependent upon their intrinsic properties. Low toxicity low solubility (LTLS) MNP are unlikely to pose a substantial cancer risk as they are not very biologically active. Nanoparticles with a more reactive surface may undoubtedly generate inflammation more readily and inflammation could be sufficiently intense to lead to secondary carcinogenesis via the oxidants and mitogens produced during inflammation. There is some evidence in vitro that MNP can gain access to the nucleus and the genetic material if specifically designed to do so by surface modification and that nanoparticles such as carbon nanotubes (CNT) can cause genetic aberrations by a primary mechanism additional to the inflammation-mediated one; these potential mechanisms require further study. High aspect ratio nanoparticles (HARN) are MNP that are fibre-shaped and analogously to asbestos might pose a special cancer hazard to the lungs, pleural and peritoneal mesothelium. Recent research suggests that the existing fibre pathogenicity paradigm is adequate for describing the hazard of HARN and that making the HARN of a non-biopersistent material or restricting the length could, via benign-by-design principles, allow safe HARN to be produced.

A comparative transmission electron microscopy study of titanium dioxide and carbon black nanoparticles uptake in human lung epithelial and fibroblast cell lines

Several studies suggest that the biological responses induced by manufactured nanoparticles (MNPs) may be linked to their accumulation within cells. However, MNP internalisation has not yet been sufficiently characterised. Therefore, the aim of this study was to compare the intracellular uptake of three different MNPs: two made of carbon black (CB) and one made of titanium dioxide (TiO2), in 16HBE bronchial epithelial cells and MRC5 fibroblasts. Transmission electron microscopy was used to evaluate the intracellular accumulation. Different parameters were analysed following a time and dose-relationship: localisation of MNPs in cells, percentage of cells having accumulated MNPs, number of aggregated MNPs in cells, and the size of MNP aggregates in cells. The results showed that MNPs were widely and rapidly accumulated in 16HBE cells and MRC5 fibroblasts. Moreover, MNPs accumulated chiefly as aggregates in cytosolic vesicles and were absent from the mitochondria or nuclei. CB and TiO2 MNPs had similar accumulation patterns. However, TiO2 aggregates had a higher size than CB aggregates. Intracellular MNP accumulation was dissociated from cytotoxicity. These results suggest that cellular uptake of MNPs is a common phenomenon occurring in various cell types.

Exploring Quantitative Nanostructure-Activity Relationships (QNAR) Modeling as a Tool for Predicting Biological Effects of Manufactured Nanoparticles

Evaluation of desired and undesired, biological effects of Manufactured NanoParticles (MNPs) is of critical importance for the future of nanotechnology. Experimental studies, especially toxicological, are time-consuming and costly, calling for the development of efficient computational tools capable of predicting biological events caused by MNPs from their structure and physical chemical properties. This mini-review assesses the potential of modern cheminformatics methods such as Quantitative Structure - Activity Relationship modeling to develop statistically significant and externally predictive models that can accurately forecast biological effects of MNPs from the knowledge of their physical, chemical, and geometrical properties. We discuss major approaches for model building and validation using both experimental and computed properties of nanomaterials. We consider two different categories of MNP datasets: (i) those comprising MNPs with diverse metal cores and organic decorations, for which experimentally measured properties can be used as particle's descriptors, and (ii) those involving MNPs possessing the same core (e.g., carbon nanotubes), but different surface-modifying organic molecules, for which computational descriptors can be calculated for a single representative of the decorative molecule. We illustrate those concepts with three case studies for which we successfully built and validated predictive models. In summary, this mini-review demonstrates that, analogous to conventional applications of QSAR modeling for the analysis of datasets of bioactive organic molecules, its application to modeling MNPs that we term Quantitative Nanostructure Activity Relationship (QNAR) modeling can be useful for (i) predicting activity profiles of novel MNPs solely from their representative descriptors and (ii) designing and manufacturing safer nanomaterials with desired properties.

A Structured Observational Method to Assess Dermal Exposure to Manufactured Nanoparticles: DREAM as an Initial Assessment Tool

Preliminary results of inventories of exposure scenarios for nanomaterials have indicated possible dermal exposure. Within the NANOSH project focused on occupational safety and health aspects of nanotechnology a shortened version of the observational DeRmal Exposure AssessMent (DREAM) method was used as an initial method to assess dermal exposure. A total of 45 tasks (such as bagging, dumping, and cleaning) involving different manufactured nanoparticles (MNPs) such as carbon nanotubes, fumed silica, and cerium oxide, were observed in industrial and research facilities. In 39 tasks potential dermal exposure (that is, exposure of the skin and clothing) was likely to occur. Exposure resulted from different routes, including direct contact with MNPs as well as the deposition or transfer of MNPs. The survey showed it is both feasible and useful to assess the potential dermal exposure using shortened DREAM questionnaires.

Quantitative Nanostructure−Activity Relationship Modeling

Evaluation of biological effects, both desired and undesired, caused by manufactured nanoparticles (MNPs) is of critical importance for nanotechnology. Experimental studies, especially toxicological, are time-consuming, costly, and often impractical, calling for the development of efficient computational approaches capable of predicting biological effects of MNPs. To this end, we have investigated the potential of cheminformatics methods such as quantitative structure-activity relationship (QSAR) modeling to establish statistically significant relationships between measured biological activity profiles of MNPs and their physical, chemical, and geometrical properties, either measured experimentally or computed from the structure of MNPs. To reflect the context of the study, we termed our approach quantitative nanostructure-activity relationship (QNAR) modeling. We have employed two representative sets of MNPs studied recently using in vitro cell-based assays: (i) 51 various MNPs with diverse metal cores (Proc. Natl. Acad. Sci. 2008, 105, 7387-7392) and (ii) 109 MNPs with similar core but diverse surface modifiers (Nat. Biotechnol. 2005, 23, 1418-1423). We have generated QNAR models using machine learning approaches such as support vector machine (SVM)-based classification and k nearest neighbors (kNN)-based regression; their external prediction power was shown to be as high as 73% for classification modeling and having an R(2) of 0.72 for regression modeling. Our results suggest that QNAR models can be employed for: (i) predicting biological activity profiles of novel nanomaterials, and (ii) prioritizing the design and manufacturing of nanomaterials toward better and safer products.

A method for determination of retention of silver and cerium oxide manufactured nanoparticles in soils

Environmental context.Soils are the environmental compartment likely to be exposed most to manufactured nanoparticles, but there is no method available at present to assess their retention, which determines potential mobility and bioavailability. Optimisation and application of a method to determine retention values for silver (Ag) and cerium oxide (CeO2) manufactured nanoparticles in soils found in many cases that they differed from the partitioning of their bulk and soluble counterparts. Wider application of this method can assist in comparing the risk of many different manufactured nanoparticles with other contaminants in soil systems and model their relationship to soil properties. Abstract.Methods to study the retention of manufactured nanoparticles (MNP) are lacking for soils that are likely to be increasingly exposed to MNP. In this study we present, for the first time, a method to determine retention values (Kr) of Ag and CeO2 MNP, that can be ranked among solid–liquid partitioning (Kd) values of bulk (micrometre-sized) forms, soluble salts and other possible contaminants of soils. After method optimisation, suspensions containing 1.24 mg kg–1 Ag as Ag MNP and 1.30 mg kg–1 Ce as CeO2 MNP were added to five soils. More than 7% of Ag MNP occurred as soluble AgI after 24 h and the range of Kr values of Ag MNP (77–2165 L kg–1) and CeO2 MNP (1.1–2828 L kg–1) contrasted with Kd values of soluble AgI, CeIII and CeIV salts and bulk Ag and CeO2 powders in different soils.

Sublethal toxicity of nano-titanium dioxide and carbon nanotubes in a sediment dwelling marine polychaete

The ecotoxicology of manufactured nanoparticles (MNPs) in estuarine environments is not well understood. Here we explore the hypothesis that nanoTiO 2 and single walled nanotubes (SWNT) cause sublethal impacts to the infaunal species Arenicola marina (lugworm) exposed through natural sediments. Using a 10 day OECD/ASTM 1990 acute toxicity test, no significant effects were seen for SWNT up to 0.03 g/kg and no uptake of SWNTs into tissues was observed. A significant decrease in casting rate ( P = 0.018), increase in cellular damage ( P = 0.04) and DNA damage in coelomocytes ( P = 0.008) was measured for nanoTiO 2, with a preliminary LOEC of 1 g/kg. Coherent anti-stokes Raman scattering microscopy (CARS) located aggregates of TiO 2 of >200 nm within the lumen of the gut and adhered to the outer epithelium of the worms, although no visible uptake of particles into tissues was detected.

Relevance of aerosol dynamics and dustiness for personal exposure to manufactured nanoparticles

Production and handling of manufactured nanoparticles (MNP) may result in unwanted worker exposure. The size distribution and structure of MNP in the breathing zone of workers will differ from the primary MNP produced. Homogeneous coagulation, scavenging by background aerosols, and surface deposition losses are determinants of this change during transport from source to the breathing zone, and to a degree depending on the relative time scale of these processes. Modeling and experimental studies suggest that in MNP production scenarios, workers are most likely exposed to MNP agglomerates or MNP attached to other particles. Surfaces can become contaminated by MNP, which constitute potential secondary sources of airborne MNP-containing particles. Dustiness testing can provide insight into the state of agglomeration of particles released during handling of bulk MNP powder. Test results, supported by field data, suggest that the particles released from powder handling occur in distinct size modes and that the smallest mode can be expected to have a geometric mean diameter >100 nm. The dominating presence of MNP agglomerates or MNP attached to background particles in the air during production and use of MNP implies that size alone cannot, in general, be used to demonstrate presence or absence of MNP in the breathing zone of workers. The entire respirable size fraction should be assessed for risk from inhalation exposure to MNP.

Insignificant acute toxicity of TiO2 nanoparticles to willow trees

Manufactured nanoparticles (MNP) are expected to increase in production in near future. In response, their environmental fate and effects are intensively studied. Phytotoxicity of some types of nanoparticles has been observed for annual species in the seed germination and root elongation test. Yet, no results of toxicity tests with trees have been reported. Woody species, dominant in many ecosystems, may be vulnerable in particular due to the large porous wood compartment. This study tests the toxicity of TiO2 nanoparticles on trees with the short-term willow tree transpiration test. TiO2 particles with 25- and 100-nm diameter were suspended in distilled water at concentrations of 0, 1, 10, and 100 mg/L (first test) and 0, 10, 20, and 50 mg/L (second test). Effects on transpiration, growth, and water use efficiency of exposed willow cuttings were monitored. The concentration of nanoparticles was measured by spectrophotometry. None of the measured effect parameters (growth, transpiration, and water use efficiency) showed any significant change during the test. Particles were rapidly lost from solution, probably due to sedimentation as a result of aggregation and also due to adsorption to roots. The loss of nanoparticles from solution was faster for particles with larger diameter and in the presence of trees. Willow trees were not sensitive to short-term exposure to TiO2 nanoparticles. Similar results were obtained for other plant species. Effects of nanoparticles were observed for zinc and zinc oxide particles, but these effects were probably due to heavy metal toxicity and not nanosize specific. In summary, we came to the conclusion that woody species are not in particular vulnerable to nanosized TiO2 particles in the conditions, concentrations, and time periods used in this study. The preliminary results of this study should be confirmed with other types of MNP, other plant species, experiments in soil and experiments combining longer duration, and low exposure concentrations before a final conclusion in this issue can be made.