Min-Kyeong Yeo

Influence of different types of nanomaterials on their bioaccumulation in a paddy microcosm: A comparison of TiO2 nanoparticles and nanotubes

We investigated the environmental fate and bioaccumulation of TiO2 nanomaterials in a simplified paddy microcosm over a period of 17 days. Two types of TiO2 nanomaterials, nanoparticles (TiO2-NP) and nanotubes (TiO2-NT), were synthesized to have a negative surface charge. Ti concentrations in the environmental media (water, soil), crops (quillworts, water dropworts), and some lower and higher trophic organisms (biofilms, algae, plant-parasitic nematodes, white butterfly larva, mud snail, ricefish) were quantified after exposure periods of 0, 7, and 17 days. The titanium levels of the two nanomaterials were the highest in biofilms during the exposure periods. Bioaccumulation factors indicated that TiO2-NP and TiO2-NT were largely transferred from a prey (e.g., biofilm, water dropwort) to its consumer (e.g., nematodes, mud snail). Considering the potential entries of such TiO2 nanomaterials in organisms, their bioaccumulation throughout the food chain should be regarded with great concern in terms of the overall health of the ecosystem.

Uptake and bioaccumulation of titanium- and silver-nanoparticles in aquatic ecosystems

Metal-based nanoparticles (NPs) such as silver (Ag) and titanium dioxide (TiO2) are widely used in industrial and household applications. Because of the increasing use of such manufactured NPs and their release into the natural environment, NPs are likely to have a widespread geographic distribution. Concerns over discharge of considerable amounts of these NPs into the environment are increasing. Although recent studies have raised concerns about the health risks and environmental impacts of NPs, little is known about their environmental fate and behavior, particularly in aquatic ecosystems, which is the final destination of NPs due to precipitation and runoff. In this review, we discuss possible routes of environmental exposure as well as the occurrence, behavior, and bioaccumulation of Ag-NPs and TiO2-NPs in the environment.

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.

Gene expression in zebrafish embryos following exposure to TiO2 nanoparticles

In this study, we investigated the effects of TiO2 nanoparticles, potential biological toxins, on zebrafish (Danio rerio) embryogenesis. We exposed zebrafish embryos to TiO2 particles of three different diameters (12–14 nm, 80–100 nm, 150–200 nm) and compared the acute responses of the embryos during embryogenesis. Scanning electron microscope (SEM) images demonstrated that 12–14 nm TiO2 particles were small ball types, while 80–100 nm TiO2 particles were square and ball types. Square layers were observed in the 150–200 nm TiO2 particles. The zebrafish morphants survived that exposure to the TiO2 nanoparticles exhibited incomplete notochord formation, with epidermal injuries observed in larvae exposed to 12–14 nm and 150–200 nm particles. In microarray analysis, several genes involved in immune response, tumor necrosis factor, and endocytosis and its regulation were differentially expressed in accordance to the nanoparticle size. Gene expression in embryos exposed to 12–14 nm particles was significantly upregulated in comparison to the control group and embryos exposed to other particle sizes. The results of the present study suggest that TiO2 nanoparticles 12–14 nm in size have toxic effects on zebraish development. TiO2 nanoparticles of larger sizes (80–100 nm, 150–200 nm) exhibit different types of genetic effects.

The effect of nano-scale Zn-doped TiO2 and pure TiO2 particles on Hydra magnipapillata

Zn-doped nano-scale TiO2 is a useful material in the production of both hydrogen energy and LEDs. However, scientists have raised concerns regarding the toxicity of nano-scale materials. In this study, we investigated the biological toxicity of nano-scale Zn (0.1, 0.5, and 1 mol%)-doped TiO2 and pure TiO2 nanoparticles using the freshwater cnidarian Hydra magnipapillata as our model organism. Zn-doped TiO2 nanoparticles were prepared using a conventional hydrothermal method for the insertion of zinc into the TiO2 framework. The character of Zn-doped TiO2 (0.1%, 0.5%, 1% Zn) and pure TiO2 was 7-8 nm with a positive surface charge. The size was smaller than that used in previous research on the toxicity of nano-scale materials. Although, in this study, we found no significant biological toxicity in Hydra magnipapillata, there was some damage under Zn-doped TiO2 and pure TiO2 UV-A photocatalysis conditions. We assessed that the damage was not linked to the nanoparticles, but rather due to the photocatalytic reaction. Moreover, Zn-doped TiO2 and pure TiO2 nanoparticles were not shown to cause cytotoxic effects, like apoptosis and necrosis that are the major markers of toxicity in organisms exposed to nanomaterials. There was no difference in necrosis or apoptosis, as viewed with a confocal laser microscope, between the Zn-doped TiO2 nanoparticleexposed group and control groups. This study suggests that particles under 10 nm in size do not exhibit biological toxicity and that the small particle size of Zndoped TiO2 and TiO2 nanoparticles decreases photocatalytic photocatalytic effect.

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 biological toxicities of two crystalline phases and differential sizes of TiO 2 nanoparticles during zebrafish embryogenesis development

In this study, we investigated the biological toxicities of two crystalline phases and differential sizes of TiO2 nanoparticles (anatase; 7–8 nm, 12–14 nm, and 17–23 nm, rutile; 80–100 nm, 150–200 nm, and 500 nm) using the zebrafish in an aquatic ecosystem. The zebrafish morphants that survived exposure to the TiO2 nanoparticles exhibited incomplete notochord formation, with epidermal malformations observed in the larvae exposed to the anatase crystal type of TiO2 nanoparticle (12–14 nm). In particular, there was more apoptosis after exposure to specific particle sizes (12–14 nm) than there was with the larger particle size (17–23 nm) of the anatase crystal type of TiO2 nanoparticles. In addition, the group exposed to the anatase crystal type TiO2 nanoparticles (7–8 nm, 12–14 nm, and 17–23 nm) showed more accumulation in the M1 phase of the cell cycle than did the control group. We observed that the TiO2 nanoparticles penetrated zebrafish larvae cells; the anatase type (12–14 nm) penetrated the nucleus, and the rutile type (80–100 nm) penetrated the mitochondria. The results of the present study suggest that the toxic effects of TiO2 nanoparticles on zebrafish embryogenesis depend on the crystalline phase and size of the nanoparticles.

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.

A fabricated microfluidic paper-based analytical device (μPAD) for in situ rapid colorimetric detection of microorganisms in environmental water samples

Abstractpaper-based analytical device (μPAD) for in situ rapid colorimetric detection of microorganisms in environmental water samples. We fabricated the μPAD with the wax printing method at curing conditions of 100°C for 7 seconds. For quick bacterial detection, we modified the catalase test with Fenton’s reaction as a colorimetric biochemical reaction. This modified catalase test provided a color indicator according to the concentration of Escherichia coli (E. coli, XL-1 Blue strain). All of the image data from the detection chamber of the μPAD was analyzed at the precision of 300 pixels for each color space component (i.e., hue, saturation, and value in HSV color). In addition, environmental samples were tested with our μPAD, and the data were fitted in the range of colorimetric reference chart for E. coli sample testing.Twenty microliters of 50% hydrogen peroxide solution was used for a single-color detection test. Before adding the E. coli sample on the chip, the detection chambers were loaded twice with 1 μL of ferrous sulfate (0.3 g/mL, 0.97 M) and dried. The mean values for all of the samples (n=10) were rounded to the nearest integer. The P values (P<0.01, P<0.05) for all three of the color space components of HSV were considered to be statistically significant.

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.