Hyung-Geun Park

Gene expression in zebrafish embryos following exposure to Cu-doped TiO2 and pure TiO2 nanometer-sized photocatalysts

We investigated the comparative effects of Cu 15 mol % doped TiO2 (anatase crystal phase, 20 ppt) nanoparticles and pure TiO2 (anatase crystal phase, 20 ppt) nanoparticles on cellular toxicity, penetration, and gene expression in zebrafish embryogenesis. HRTEM analysis observed that pure TiO2 particles were in the form of small balls (<10 nm), while Cu-doped (15 mol %) TiO2 particles were large (20–70 nm) squares and balls. Both Cu/TiO2 and pure TiO2 nanoparticles penetrated into cells. Cu/TiO2 nanoparticles penetrated into the yolk sac epithelial cells of zebrafish larvae as aggregated particles. Mitochondria in embryos exposed to Cu/TiO2 nanoparticles were damaged and did not contain cristae. In microarray analysis, several genes involved in apoptosis and endocytosis regulation were differentially expressed according to nanoparticle type. Bcl2 gene expression was significantly upregulated in embryos exposed to both Cu/TiO2 and pure TiO2 in comparison to the control group. Cu/TiO2 nanoparticles caused more damage than pure TiO2 nanoparticles and resulted in apoptosis during zebrafish development.

Comparison of gene expression changes induced by exposure to Ag, Cu-TiO 2 , and TiO 2 nanoparticles in zebrafish embryos

Nanomaterials composed of silver (Ag), copper-doped titanium dioxide (Cu-TiO2), and pure titanium dioxide (TiO2) have wide applications in consumer products such as cosmetics, electronic appliances, clothes, and industry materials such as solar cell. However, there are problems associated with the exposure of aquatic organisms in the ecosystem to such nanomaterials. In this study, we investigated the expression pattern of genes in zebrafish embryos after exposure to nanomaterials. We used several functional categories including apoptosis, endocytosis, immune response, and endoplasmic reticulum stress so on. A total of 314 (278 up-regulated and 36 down-regulated), 283 (129 up-regulated and 154 down-regulated), and 360 (198 up-regulated and 162 down-regulated) genes were differentially expressed in zebrafish embryos exposed to Ag, Cu-TiO2, and TiO2 NPs, respectively, with apoptosis being the function of the highest proportion of differentially expressed genes in all 3 NP exposures. Our data provide a basis for conducting further mechanistic studies of genes that are induced or suppressed upon exposure to NPs in zebrafish embryogenesis.

The toxicity of triclosan, bisphenol A, bisphenol A diglycidyl ether to the regeneration of cnidarian, Hydra magnipapillata

Triclosan, bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE) are widely used in cosmetics, cleaners and plastic bowls. However, triclosan has been detected in sewage samples after treatment. Moreover, BPA and BADGE are thought to be endocrine disruptors, and these chemicals bio-accumulate in aquatic living organisms. Human skin and oral tissues are commonly exposed to phenolic chemicals such as triclosan, BPA and BADGE. These types of cells have an excellent regeneration capacity. Hydra magnipapillata inhabits rivers and ponds, and is widely used as a test species because of its ability to rapidly regenerate. Therefore, we investigated the biological toxicity of phenolic chemicals (triclosan, BPA and BADGE) using the freshwater cnidarian, Hydra magnipapillata. We observed severe biological damage after exposure to 1-5 ppm of each of the phenolic chemicals tested. In the Hydra magnipapillata exposed to triclosan (1 ppm, 4 h), there was epidermal tissue and nematocyst damage. Although we did not observe significant biological toxicity in regenerated tissue from Hydra magnipapillata treated with BPA and BADGE, the regeneration capacity was inhibited in the group exposed to triclosan. Hydra tentacles that were treated with phenolic chemicals (1 ppm, 4 h) were moved to a control medium in order to assess recovery after exposure to triclosan, BPA and BADGE. There was no significant difference between the treated and control groups. Moreover, there was no difference in apoptosis, as viewed with a confocal laser microscope, between the endocrine-disrupting phenolic chemicalexposed groups and regeneration groups. The results of this study suggest that BPA and BADGE do not exhibit biological toxicity, but triclosan has toxic effects on the cellular reproduction process that is part of regeneration in Hydra magnipapillata.

Paper-based microfluidic device for bisphenol A based chemical reaction and image analysis

Bisphenol A (BPA) is a representative xenoestrogenic endocrine disruptor that is widely used in consumer products and remains in wastewater. A simple detection tool is urgently needed that can be used with the naked eye for environmental monitoring in situ. Therefore we studied modification methods of phenol and ferric reagents on a paper-based microfluidic device. The reaction between BPA and ferric reagent mixtures was examined using two types of ferric reagent mixtures (ferric chloride/ferricyanide and ferric nitrate/ferricyanide) at various ferric reagent mixture ratios (1 : 9, 3 : 7, 5 : 5, 7 : 3 and 9 : 1) and concentrations (BPA 100, 300, 500 and 1000 μg/mL and 1-5% ferric reagent mixtures). Verification of this paper-based microfluidic device was analyzed with a UV spectrophotometer.In addition, the changing color of the BPA reaction was demonstrated using histograms of the image statistics including the hue, saturation and value (HSV) analysis. Of the total BPA reactions, the optimal condition was identified as 1% ferric reagent mixture (5: 5 ratio) and 5 μL of BPA loaded onto the paper-based microfluidic device. Moreover, the BPA detection abilities of ferric chloride/ferricyanide and ferric nitrate/ferricyanide were similar to the changing images on the paper-based microfluidic device. The BPA paperbased microfluidic device is expected to be applied in situ and in factories as a low-cost, portable, simple and rapid detection system.

The effect of metal-doped TiO2 nanoparticles on zebrafish embryogenesis

In this study, we manufactured metal-doped TiO2 nanoparticles using several transition metals (Mn, Fe, Ni, and Cu). Their physicochemical properties were evaluated by transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, and UV-visible spectra. The energy efficiency of the metals increased in the order of Ni-<Cu-<Mn-<Fe-TiO2. For toxicity testing, zebrafish embryos were exposed to 4 mg L−1 of metal-doped TiO2 nanoparticles. We determined the survival rate (%) and abnormal morphology rate (%) of the exposed embryos and also observed apoptosis and necrosis using confocal microscopy. The metal TiO2 nanoparticles showed acute toxicity in the order of Mn-<Cu-<Ni-≤Fe-TiO2. Although the Fe-TiO2 NPs group demonstrated the highest photocatalytic performance, it also exhibited the highest toxic effects. Among the metals, the Mn-TiO2 NPs group demonstrated improved photocatalysis compared to the other samples except for the Fe-TiO2 NPs along with the lowest toxic effects. For these reasons, the most suitable doping metal was the Mn-TiO2 NPs group considering its energy activity and environmental impacts.

Nanomaterial regulatory policy for human health and environment

The world today is enhanced by imposing trade regulations on various chemicals including nanomaterials. In particular, nanomaterials have different physicochemical property unlike general chemicals, it has become a controversial issue due to concerns related to human health and environment. Due to the potential risks of nanomaterials, most developed countries have actively joined members of international organizations (Organization for Economic Co-operation and Development the Working Party on Manufactured Nanomaterials (OECD WPMN), International Organization for Standardization / Technical Committee 229 (ISO/TC 229), Registration, Evaluation, Authorization and Restriction of Chemicals Annex (REACH Annex), etc.). These international organizations have been making nanomaterial test guidelines and standardization work. There are also strengthened by trade regulations that ensure the safe distribution of nanomaterials. Representatives of the EPA’s FIFRA have been collecting information about and carrying out the conditional registration of nano-silver products. Alternatively, The Korean government is taking action internationally by being an active member of the OECD and ISO. Considering nanotechnology and nano-safety, The Korean government is planning to control domestic polices such as the nano-safety management plan and Korea REACH (in addition to their international activities). However, despite all these efforts, the Republic of Korean market does not have nano-regulations related to the uses of industries and consumer products of nanomaterials. Such nano-regulations should be implemented in consumer products as soon as possible. Herein, we investigated recent trends concerning the domestic and foreign policies of nanomaterials, which should be utilized in the nano-safety plans of each country. This paper prepares relevant nanomaterial policies and presents the worldwide regulations that concern nanomaterials.

Effects of TiO2 nanoparticles and nanotubes on zebrafish caudal fin regeneration

Nanophase ceramic titanium dioxide (TiO2) is a potential scaffold material for tissue engineering. When scaffolds are used to regenerate injured tissues or organs, potential adverse effects associated with the scaffolding material should be investigated. This study focused on the influx and accumulation of TiO2 nanoparticles (NPs)- and TiO2 nanotubes (NTs)- and the resulting damage to zebrafish caudal fin regeneration. The effects of these nanomaterials on apoptosis or necrosis during embryogenesis were also investigated. NPs and NTs induced asymmetric regeneration of fins at 1 mg/L, and apoptosis was observed in zebrafish embryos exposed to NPs and NTs at 20 ng/L. Significantly more TiO2-NPs and TiO2-NTs accumulated in reproductive organs and intestines of fish with amputated fins, suggesting that TiO2-NPs and TiO2-NTs cause undesired tissue accumulation and toxicity. Thus, bioaccumulation of TiO2 nanomaterials in intestine and reproductive organs via injured tissue could be a potential developmental risk.

Comparison of gene expression patterns from zebrafish embryos between pure silver nanomaterial and mixed silver nanomaterial containing cells of Hydra magnipapillata

Silver nanomaterials have potentially toxic effects in aquatic organisms. However, lower toxicity was demonstrated in hydra exposed to high concentrations of silver nanomaterials. Moreover, aggregated nanomaterials were shown to be excreted from hydra. These excreted nanomaterials had an increased particle size and changed particle shapes compared to the native particles. In addition, the changed nanomaterials were shown to convey reduced toxicity. To investigate the effect of hydra extract on changes in nanotoxicity, we formed a mixed silver nanomaterial that included hydra cells. We investigated the nanotoxicity of this mixture on zebrafish embryogenesis, because zebrafish have very high sensitivity to environmental conditions. The survival rate of embryos in the mixed nano groups was higher than that in the pure nano groups. We also compared the gene expression patterns between pure silver nanomaterials and mixed silver nanomaterials in zebrafish embryos using microarray analysis. We identified the metabolic and cellular processes that had altered gene expression. Genes related to apoptosis were overexpressed in the pure silver nano groups, and genes involved in the immune system had lower expression compared to the mixed silver nano groups.

Trophic transfer of citrate, PVP coated silver nanomaterials, and silver ions in a paddy microcosm

We used replicated paddy microcosm systems to estimate the tropic transfer of citrate-coated silver nanoparticles (AgNP citrate), polyvinylpyrrolidone (PVP)-coated AgNP (AgNP PVP), and silver ions (AgNO3) for 14 days under two exposure regimes (a single high-dose exposure; 60 μg L-1 and a sequential low-dose exposure at 1 h, 4 days and 9 days; 20 μg L-1 × 3 = 60 μg L-1). Most Ag ions from AgNO3 had dispersed in the water and precipitated partly on the sediment, whereas the two Ag NPs rapidly coagulated and precipitated on the sediment. The bioconcentration factors (BCFs) of Ag from AgNPs and AgNO3 in Chinese muddy loaches and biofilms were higher than those of river snails in both exposure conditions. These BCFs were more prominent for 14 days exposure (7.30 for Chinese muddy loach; 4.48 for biofilm) in the low-dose group than in the single high-dose group. Their retention of AgNPs and Ag ions differed between the two exposure conditions, and uptake and elimination kinetics of Ag significantly differed between AgNP citrate and AgNP PVP in the sequential low-dose exposure. Stable isotopes analyses indicated that the trophic levels between Chinese muddy loaches and biofilms and between river snails and biofilms were 2.37 and 2.27, respectively. The biomagnification factors (BMFs) of AgNPs and AgNO3 between Chinese muddy loaches and biofilms were significantly higher than those between river snails and biofilms under both exposure settings. The BMFs of AgNP citrate and AgNO3 between Chinese muddy loaches and biofilms were greater than those of AgNP PVP for 14 days in the single high-dose group, whereas the BMFs of AgNP PVP were greater than those of AgNP citrate and AgNO3 in the sequential low-dose group. These microcosm data suggest that AgNPs have the potential to impact on ecological receptors and food chains.

Chemical management policies and a distribution model for chemical accidents

This study compares and evaluates domestic and overseas chemical substance management systems, and compares domestic risk management systems and overseas cases regarding issues and vulnerabilities to propose a plan for improving these issues. The Chemical Substance Control Act is a more powerful law than the chemical substance control acts of other countries, but it requires a seamless system and information sharing between managing government agents to correct overlaps in the reporting system for chemical substance management. A comparison of chemical substance dispersion models finds that ALOHA, from the United States, fails to include environmental factors such as topographical changes and atmospheric conditions and does not consider the reactions of chemical substances in the atmosphere or the variables involved in granular chemical substances and mixtures. The Korean model (KORA) has the advantage of automatically completing risk assessments and scenarios for each accident type. However, it has the inconvenience of requiring users to directly input the target of protection in the event of a chemical accident. Overall, a chemical substance risk management system must include information about the toxicity of chemical substances and environmental factors.