Woo-Mi Lee

Toxicity and bioavailability of copper nanoparticles to the terrestrial plants mung bean (Phaseolus radiatus) and wheat (Triticum aestivum): Plant agar test for water-insoluble nanoparticles†

Because of their insolubility in water, nanoparticles have a limitation concerning toxicity experiments. The present study demonstrated a plant agar test for homogeneous exposure of nanoparticles to plant species. The effect of Cu nanoparticles on the growth of a plant seedling was studied, and bioaccumulation of nanoparticles was investigated. All tests were conducted in plant agar media to prevent precipitation of water-insoluble nanoparticles in test units. The plant species were Phaseolus radiatus (mung bean) and Triticum aestivum (wheat). Growth inhibition of a seedling exposed to different concentrations of Cu nanoparticles was examined. Copper nanoparticles were toxic to both plants and also were bioavailable. The 2-d median effective concentrations for P. radiatus and T. aestivum exposed to Cu nanoparticles were 335 (95% confidence level, 251-447) and 570 (450-722) mg/L, respectively. Phaseolus radiatus was more sensitive than T. aestivum to Cu nanoparticles. A cupric ion released from Cu nanoparticles had negligible effects in the concentration ranges of the present study, and the apparent toxicity clearly resulted from Cu nanoparticles. Bioaccumulation increased with increasing concentration of Cu nanoparticles, and agglomeration of particles was observed in the cells using transmission-electron microscopy-energy-dispersive spectroscopy. The present study demonstrated that the plant agar test was a good protocol for testing the phytotoxicity of nanoparticles, which are hardly water soluble.

Effect of silver nanoparticles in crop plants Phaseolus radiatus and Sorghum bicolor: Media effect on phytotoxicity

Understanding some adverse effects of nanoparticles in edible crop plants is a matter of importance because nanoparticles are often released into soil environments. We investigated the phytotoxicity of silver nanoparticles (AgNPs) on the important crop plants, Phaseolus radiatus and Sorghum bicolor. The silver nanoparticles were selected for this study because of their OECD designation as a priority nanomaterial. The toxicity and bioavailability of AgNPs in the crop plant species P. radiatus and S. bicolor were evaluated in both agar and soil media. The seedling growth of test species was adversely affected by exposure to AgNPs. We found evidence of nanoparticle uptake by plants using electron microscopic studies. In the agar tests, P. radiatus and S. bicolor showed a concentration dependent-growth inhibition effect. Measurements of the growth rate of P. radiatus were not affected in the soil studies by impediment within the concentrations tested herein. Bioavailability of nanoparticles was reduced in the soil, and the dissolved silver ion effect also differed in the soil as compared to the agar. The properties of nanoparticles have been shown to change in soil, so this phenomenon has been attributed to the reduced toxicity of AgNPs to plants in soil medium. The application of nanoparticles in soil is a matter of great importance to elucidate the terrestrial toxicity of nanoparticles.

Effects of zinc oxide and titanium dioxide nanoparticles on green algae under visible, UVA, and UVB irradiations: No evidence of enhanced algal toxicity under UV pre-irradiation

Some metal oxide nanoparticles are photoreactive, thus raising concerns regarding phototoxicity. This study evaluated ecotoxic effects of zinc oxide nanoparticles and titanium dioxide nanoparticles to the green algae Pseudokirchneriella subcapitata under visible, UVA, and UVB irradiation conditions. The nanoparticles were prepared in algal test medium, and the test units were pre-irradiated by UV light in a photoreactor. Algal assays were also conducted with visible, UVA or UVB lights only without nanoparticles. Algal growth was found to be inhibited as the nanoparticle concentration increased, and ZnO NPs caused destabilization of the cell membranes. We also noted that the inhibitory effects on the growth of algae were not enhanced under UV pre-irradiation conditions. This phenomenon was attributed to the photocatalytic activities of ZnO NPs and TiO2 NPs in both the visible and UV regions. The toxicity of ZnO NPs was almost entirely the consequence of the dissolved free zinc ions. This study provides us with an improved understanding of toxicity of photoreactive nanoparticles as related to the effects of visible and UV lights.

Zinc oxide nanoparticles delay soybean development: A standard soil microcosm study

Soybean is an important crop and a source of food for humans and livestock. In this study, for the first time, the long-term effects of zinc oxide (ZnO) nanoparticles on the growth, development, and reproduction of soybean [Glycine max (L.) Merrill] were evaluated in a standard soil microcosm study. The soil was treated with 0, 50, or 500 mg/kg (dry weight) of ZnO nanoparticles. The growth and development of soybean plants were tracked during a cultivation period of 8-9 weeks under greenhouse conditions. Soybean development was damaged in both treatment groups, particularly in the group that received 500 mg/kg ZnO nanoparticles. In comparison with the control group, the roots and shoots of soybeans in treatment groups were shorter and had smaller surface area and volume. Furthermore, the plants in the 500 mg/kg treatment group did not form seeds. ZnO nanoparticles negatively affected the developmental stages and reproduction of soybean plants in a soil microcosm.

Effect of fluorescent silica nanoparticles in embryo and larva of Oryzias latipes: Sonic effect in nanoparticle dispersion

We characterized fluorescent silica nanoparticles (FNPs), which had been applied in many biological systems, in fish embryo rearing media (ERM) solution and evaluated the potential toxicity to the early development of Oryzias latipes embryos. Distribution of FNPs in embryos and larvae of O. latipes was studied by fluorescent and confocal laser scanning microscopic studies. Embryos exposed to three different concentrations of FNPs in stirred or sonicated ERM solutions were observed up to 2d after hatching. FNPs had a negligible effect on the hatchability of O. latipes embryos; however, compared to controls, more than 30% of eggs were abnormal in 10 and 50 mg FN P L(-1) solutions. We found that the toxic effect was increased in sonicated FNP solution, which seems to be related with the dissolution of FNPs in ERM solutions that could be accelerated by sonication. Further study found that the CaCl2 included in ERM solution might enhance the dissolution of the FNPs and the silicate ion released from FNPs partially contributed to larval toxicity. This study showed that some nanoparticles may not be stable in biological fluids even if they are stable in water. Dissolution factors such as sonication and cellular components should be considered in biological application of nanoparticles.

Evidence of three-level trophic transfer of quantum dots in an aquatic food chain by using bioimaging

Abstract In this study, we demonstrated the three-level trophic transfer of quantum dots (QDs) within the aquatic food chain. Using bioimaging, we observed QD transfer from protozoa (Astasia longa) to zooplankton (Moina macrocopa) to fish (Danio rerio). Bioimaging is an effective tool that can improve our understanding of the delivery of nanomaterials in vivo. Measurement with an intravital multiphoton laser scanning microscope visually proved the transfer of QDs from the first to the second and the second to the third levels. As QDs may be passed from lower organisms to humans via the food chain, our findings have implications for the safety of their use.

Interaction of citrate-coated silver nanoparticles with earthworm coelomic fluid and related cytotoxicity in Eisenia andrei

Understanding the interaction of nanoparticles with biological fluid is important for predicting the behavior and toxicity of nanoparticles in living systems. The earthworm Eisenia andrei was exposed to citrate‐coated silver nanoparticles (cAgNPs), and the interaction of cAgNPs with earthworm coelomic fluid (ECF), the cytotoxicity of cAgNPs in earthworm coelomocytes was assessed. The neutral red retention assay showed a reduction in lysosomal stability after exposure. The toxicity of silver ions dissolved from cAgNPs in the soil medium was not significant. The aggregation and dissolution of cAgNPs increased in ECF, which contains various electrolytes that alter the properties of nanoparticles, and their subsequent toxicity. Microscopic and dissolution studies demonstrated that the aggregation of cAgNPs rapidly increased, and readily dissolved in ECF. The bioavailability of cAgNPs to earthworms induced lysosomal cytotoxicity. This is the first report to test the interaction and lysosomal cytotoxicity of nanoparticles in earthworm biofluids. Copyright

Research Trends of Ecotoxicity of Nanoparticles in Soil Environment

We are consistently being exposed to nanomaterials in direct and/or indirect route as they are used in almost all the sectors in our life. Nations across the worlds are now trying to put global regulation policy on nanomaterials. Sometimes, they are reported to be more toxic than the corresponding ion and micromaterials. Therefore, safety research of nanoparticles has huge implications on a national economics. In this study, we evaluated and analyzed the research trend of ecotoxicity of nanoparticles in soil environment. Test species include terrestrial plants, earthworms, and soil nematode. Soil enzyme activities were also discussed. We found that the results of nanotoxicity studies were affected by many factors such as physicochemical properties, size, dispersion method and test medium of nanoparticle, which should be considered when conducting toxicity researches. In particular, more researches on the effect of physico chemical properties and fate of nanoparticles on toxicity effect should be conducted consistently.

Ecological effects of soil antimony on the crop plant growth and earthworm activity

High levels of antimony have been frequently detected in some industrial sites. This study evaluated the adverse effects of antimony (Sb) on the surface-casting activity of earthworm and the early growths of some important crop plants. Asian earthworm (Perionyx excavates) and four crop plant species (Chinese cabbage, Brassicacampestris; wheat, Triticum aestivum; cucumber, Cucumis sativus; and mung bean, Phaseolus radiatus) were exposed to soil antimony in laboratory. Survival, abnormality and the surface-casting activity of earthworm were monitored. Negative effects of the survival and the morphological abnormalities were observed in the P. excavates exposed to Sb. The earthworm activity, expressed as surface cast production, was significantly inhibited with elevated Sb levels. In terms of plant assay, the growth of all test plants was adversely affected in Sb-contaminated soils, and the content of Sb in plant tissues increased with increasing Sb concentration in soil. The results demonstrate that elevated Sb concentrations in soil would inhibit the early growth of crop plants, and the earthworm casting activity that is a key function of earthworm to increase soil fertility. This is the first report on the negative effect of Sb on the casting activity of earthworm as well as the growth of test plant species selected.

Conducting a battery of bioassays for gold nanoparticles to derive guideline value for the protection of aquatic ecosystems

Abstract Gold nanoparticles (Au-NPs) are used in many applications, including the manufacture of products like cosmetics, paints, and electrochemical immunosensors, and in the detection, diagnosis, and treatment of tumors. However, there are no legal or recommended guidelines for protecting aquatic ecosystems from Au-NPs. In this study, we conducted a battery of bioassays and present toxicity values for two bacteria, one alga, one euglena, three cladoceran, and two fish species that were exposed to Au-NPs. Guideline values for protecting aquatic ecosystems from Au-NPs were derived using methods that are generally used to derive water-quality guidelines and are used in Australia, New Zealand, Canada, the European Community (EC), and the USA. Au-NPs had adverse effects on all test species, including growth inhibition of both bacteria, the alga, and the euglena; mortality and immobilization in the three cladocerans; and developmental malformations in the embryos and larvae of the two fish. Guideline values of 0.15 and 0.04 × 1010 particles/mL were derived for Au-NPs using a species sensitivity distribution (SSD) and assessment factor. The guideline value derived for Au-NPs using an assessment factor was more stringent than that derived using SSD. This is the first study to derive guideline values for nanoparticles in water environments.