Jin Il Kwak

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.

Multigenerational study of gold nanoparticles in Caenorhabditis elegans: transgenerational effect of maternal exposure.

In this study, the generational transfer and multigenerational effect of gold nanoparticles (AuNPs) on Caenorhabditis elegans were investigated by observing the parental generation (F0) to the fourth offspring generation (F4) using food-exposure approaches. There were no significant changes on survival rate under all generations by AuNP maternal exposure to the F0 generation. However, reproduction rate was clearly affected in the F2 generation but then gradually recovered in the F3 and F4 generations. The abnormalities of the reproductive system showed a close relationship with reproduction rates. These phenomenons may be due to the germ-line transfer. The germ line of F0 generation such as gonad and embryo germ cell may be affected during their development by maternal exposure of AuNPs, and this generation caused transgeneration effect on future generations. To the best of our knowledge, this is the first study to provide the evidence of transgenerational effects by maternal exposure of nanoparticles to the next generations.

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.

Evidence for the inhibitory effects of silver nanoparticles on the activities of soil exoenzymes

Silver nanoparticles (AgNPs) are well known to have antimicrobial ability, but very little is known about the effect of AgNPs on soil exoenzyme activities, which reflect the potential of a soil to support biochemical processes. This study provides evidence of the inhibitory effects of AgNPs on the activities of soil exoenzymes. Six exoenzymes related to nutrient cycles (urease, acid phosphatase, arylsulfatase, β-glucosidase) and the overall microbial activity (dehydrogenase, fluorescein diacetate hydrolase) were tested in soils treated with AgNPs (1, 10, 100 and 1000 μg g(-1)) and silver ion (0.035, 0.175, 0.525, 1 and 1.5 μg g(-1)). AgNPs were capable of inhibiting the activities of all the exoenzymes tested in this study. Especially, the urease and dehydrogenase activities were significantly related to the presence of AgNPs. The effects of silver ions dissolved from the AgNPs were not significant, indicating the adverse effects caused by AgNPs themselves. This study suggested that AgNPs negatively affect soil exoenzyme activities, with the urease activity especially sensitive to AgNPs.

The current state of the art in research on engineered nanomaterials and terrestrial environments: Different-scale approaches

Recent studies regarding the environmental fate of engineered nanomaterials (ENMs) reported that most ENMs were eventually deposited in landfills. Therefore, it is important to evaluate the environmental effects of ENMs on soils through long-term and environmentally relevant studies. Our review of 65 studies published since 2007 revealed that ENMs had adverse effects on terrestrial species, including soil microorganisms, plants, and earthworms. The papers reported the results of soil toxicity tests for ENMs at the microcosm and mesocosm levels, in the field, and through food chains, as well as their effects on species sensitivity distributions. Little research has been conducted on the interaction between ENMs and actual environmental conditions, such as their effects on a community of multiple species or species sensitivity distributions. Few studies have used mesocosms, and only a single study has been conducted in the field. The present review provides a broad perspective on the impact of ENMs on soil organisms as reported in the literature and highlights directions for future work.

A new and sensitive method for measuring in vivo and in vitro cytotoxicity in earthworm coelomocytes by flow cytometry

This study describes a new and sensitive method for measuring the in vivo and in vitro cytotoxicity of 2 earthworm species, Eisenia andrei and Perionyx excavatus, exposed to copper. Specifically, we measured the number of coelomocyte cells that were affected by copper following in vivo and in vitro exposure by flow cytometry, after calcein acetoxymethyl ester (calcein-AM) staining. We found that the coelomocyte viability of both earthworm species was noticeably reduced in the in vivo cytotoxicity test at concentrations of 100mg/kg copper in dry soil. However, pathological symptoms, such as mucous secretion and bleeding, swelling, thinning, and fragmentation, and burrowing symptoms were not evident following exposure to copper levels of <400mg/kg dry soil. In conclusion, the present study demonstrates that calcein-AM is a more sensitive test of earthworm coelomocyte cytotoxicity compared to the traditional individual level toxicity test. Therefore, this test could be used to detect low levels of metal contamination in soils.

Multispecies toxicity test for silver nanoparticles to derive hazardous concentration based on species sensitivity distribution for the protection of aquatic ecosystems

Abstract With increasing concerns about the release of silver nanoparticles (AgNPs) into the environment and the risks they pose to ecological and human health, a number of studies of AgNP toxicity to aquatic organisms have been conducted. USEPA and EU JRC have published risk assessment reports for AgNPs. However, most previous studies have focused on the adverse effects of AgNPs on individual species. Hazardous concentration (HC) of AgNPs for protection of aquatic ecosystems that are based on species sensitivity distributions (SSDs) have not yet been derived because sufficient data have not been available. In this study, we conducted multispecies toxicity tests, including acute assays using eight species from five different taxonomic groups (bacteria, algae, flagellates, crustaceans and fish) and chronic assays using six species from four different taxonomic groups (algae, flagellates, crustaceans and fish). Using the results of these assays, we used a SSD approach to derive an AgNP aquatic HC5 (Hazard concentrations at the 5% species) of 0.614 μg/L. To our knowledge, this is the first report of a proposed HC of AgNPs for the protection of aquatic ecosystems that is based on SSDs and uses chronic toxicity data.

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.

Trophic transfer of silver nanoparticles from earthworms disrupts the locomotion of springtails (Collembola)

Understanding how nanomaterials are transferred through food chains and evaluating their resulting toxicity is important. However, limited research has been conducted on the toxic consequences of trophically transferred nanomaterials in terrestrial ecosystems. In this study, we documented the adverse effects of trophically transferred silver nanoparticles (AgNPs) in a soil-earthworm (Eisenia andrei)-Collembola (Lobella sokamensis) food chain. We exposed E. andrei to soil with AgNPs at concentrations of 50, 200, and 500μg AgNPs/g soil dry weight and assessed their survival after 7days. Trophic-transfer containers were then prepared and E. andrei that survived the 7days test period were washed, killed in boiling water, and added to the containers with L. sokamensis. We noted negligible effects and low bioaccumulation at the lowest AgNP concentration (50μg AgNPs/g soil dry weight) in earthworms and the L. sokamensis that fed on them. The highest concentration of AgNPs (500μg AgNPs/g soil dry weight) resulted in juvenile earthworm mortality and increased transfer of AgNPs to Collembola, which subsequently inhibited their locomotion. To our knowledge, this is the first study to document the trophic transfer and adverse effects of AgNPs in a soil-earthworm-Collembola food chain, a common prey-decomposer interaction in soil ecosystems.