Shin Woong Kim

Interaction of Silver Nanoparticles with Biological Surfaces of Caenorhabditis elegans

Silver nanoparticles (AgNPs) are being used in an increasing number of industrial and commercial applications; this has resulted in an increased release of AgNPs into the environment. Understanding the interaction of AgNPs with biological surfaces is important, as such understanding will facilitate predictions of the further effects of nanoparticles on biological systems. This study highlights the interaction of citrate-coated silver nanoparticles (cAgNPs) with the biological surfaces of the nematode C. elegans. General toxicity, as proxied by factors such as mortality and reproduction, was evaluated in nematode growth medium (NGM), which provides a more homogeneous distribution of cAgNPs than in K-medium. The survival and reproduction of C. elegans evidenced a clear reduction in up to 100 mg/L and 10 mg/L of cAgNPs, respectively. We also noted significant interactions of cAgNPs with the biological surfaces of C. elegans. Severe epidemic edema and burst were detected in the exposure group, which may be associated with secondary infections in soil ecosystems. We observed no evidence of cAgNPs intake by C. elegans. This is, to the best of our knowledge, the first report to investigate the nanotoxicity of cAgNPs as related to biological surfaces of C. elegans; further research is needed to study the fate of cAgNPs inside of C. elegans.

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.

Assay-dependent effect of silver nanoparticles to Escherichia coli and Bacillus subtilis

We assess the microbial assay-dependent effect of AgNP on gram-negative Escherichia coli and gram-positive Bacillus subtilis. The experiment was conducted via three different assays: a growth inhibition assay, a colony forming unit assay, and a liquid-to-plate assay. AgNP were exposed either as liquid suspensions or in an agar state. Bacterial sensitivity to AgNP was found to be dependent on the microbial assay employed. E. coli was more sensitive than B. subtilis in the growth inhibition and CFU assays, but B. subtilis was more vulnerable than E. coli in the liquid-to-plate assay, ostensibly owing to the food stress mechanisms of B. subtilis in exposure medium. The dissolution of silver from AgNP could not explain the observed toxicity of AgNP. We detected clear evidence of AgNP uptake by cells. The results of this study showed that the microbial toxicity of AgNP and the effects of dissolved silver ions were influenced profoundly by the microbial test method employed.

No evidence of the genotoxic potential of gold, silver, zinc oxide and titanium dioxide nanoparticles in the SOS chromotest.

Gold nanoparticles (Au NPs), silver nanoparticles (Ag NPs), zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO2 NPs) are widely used in cosmetic products such as preservatives, colorants and sunscreens. This study investigated the genotoxicity of Au NPs, Ag NPs, ZnO NPs and TiO2 NPs using the SOS chromotest with Escherichia coli PQ37. The maximum exposure concentrations for each nanoparticle were 3.23 mg l–1 for Au NPs, 32.3 mg l–1 for Ag NPs and 100 mg l–1 for ZnO NPs and TiO2 NPs. Additionally, in order to compare the genotoxicity of nanoparticles and corresponding dissolved ions, the ions were assessed in the same way as nanoparticles. The genotoxicity of the titanium ion was not assessed because of the extremely low solubility of TiO2 NPs. Au NPs, Ag NPs, ZnO NPs, TiO2 NPs and ions of Au, Ag and Zn, in a range of tested concentrations, exerted no effects in the SOS chromotest, evidenced by maximum IF (IFmax) values of below 1.5 for all chemicals. Owing to the results, nanosized Au NPs, Ag NPs, ZnO NPs, TiO2 NPs and ions of Au, Ag and Zn are classified as non‐genotoxic on the basis of the SOS chromotest used in this study. To the best of our knowledge, this is the first study to evaluate the genotoxicity of Au NPs, Ag NPs, ZnO NPs and TiO2 NPs using the SOS chromotest. Copyright

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 and individual impact of nano-sized polystyrene in a four-species freshwater food chain

This study investigated the trophic transfer, individual impact, and embryonic uptake of fluorescent nano-sized polystyrene plastics (nanoplastics) through direct exposure in a freshwater ecosystem, with a food chain containing four species. The alga Chlamydomonas reinhardtii, water flea Daphnia magna, secondary-consumer fish Oryzias sinensis, and end-consumer fish Zacco temminckii were used as test species. In the trophic transfer test, algae were exposed to 50 mg/L nanoplastics, defined as plastic particles <100 nm in diameter; higher trophic level organisms were exposed through their diet. In the direct exposure test, each species was directly exposed to nanoplastics. Microscopic analysis confirmed that the nanoplastics adhered to the surface of the primary producer and were present in the digestive organs of the higher trophic level species. Nanoplastics also negatively affected fish activity, as measured by distance traveled and area covered, and induced histopathological changes in the livers of fish that were directly exposed. Additionally, nanoplastics penetrated the embryo walls and were present in the yolk sac of hatched juveniles. These observations clearly show that nanoplastics are easily transferred through food chain, albeit because of high experimental dosages. Nevertheless, the results strongly point to the potential health risks of nanoplastic exposure.

Polystyrene nanoplastics inhibit reproduction and induce abnormal embryonic development in the freshwater crustacean Daphnia galeata

We assayed the toxicity of polystyrene nanoparticles (PS-NP, 52 nm) to Daphnia galeata. Survival and reproduction were significantly decreased in individuals exposed to 5 mg/L of PS-NP for 5 days, and embryos showed abnormal development, including a low hatching rate. Using fluorescence confocal microscopy, we recorded the transfer of PS-NP from the external surface of the body to the internal organs, including the thoracic appendices, ovaries, caudal appendices, and brood chamber, as well as PS-NP storage in lipid droplets. Although embryos were exposed to PS-NP in the brood chamber, they did not internalize PS-NP. Exposed D. galeata adults that were not pregnant stored significantly fewer lipid droplets than did the control group, and the lipid droplets that they did store were smaller; meanwhile, there were no significant changes in lipid storage in exposed pregnant individuals. Some embryos showed a high level of lipid storage, a response that occurs when embryos experience an abnormal state, and these embryos showed a very low hatching rate. However, the offspring of exposed adults showed normal survival and lipid storage. This study provides visual evidence that confirms the transfer and effects of PS-NP in Daphnia species, and suggests a relationship between toxicity and lipid storage.