Ig-chun Eom

Combined repeated-dose toxicity study of silver nanoparticles with the reproduction/developmental toxicity screening test

Abstract Combined repeated-dose toxicity study of citrate-capped silver nanoparticles (7.9 ± 0.95 nm) with reproduction/developmental toxicity was investigated in rats orally treated with 62.5, 125 and 250 mg/kg, once a day for 42 days for males and up to 52 days for females. The test was performed based on the Organization for Economic Cooperation and Development test guideline 422 and Good Laboratory Practice principles. No death was observed in any of the groups. Alopecia, salivation and yellow discolouration of the lung were observed in a few rats but the symptoms were not dose-dependent. Haematology, serum biochemical investigation and histopathological analysis revealed no statistically significant differences between control group and the treated groups. Toxicity endpoints of reproduction/developmental screening test including mating, fertility, implantation, delivery and foetus were measured. There was no evidence of toxicity.

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.

Serum and ultrastructure responses of common carp (Cyprinus carpio L.) during long-term exposure to zinc oxide nanoparticles

The uptake of nanoparticles by aquatic organisms such as fish has raised concerns about the possible adverse effects of nanoparticles (NPs). In this study, we aimed to evaluate the toxicological effects in juvenile common carp exposed to zinc oxide nanoparticles (ZnO-NPs) for 12 weeks. The carp were exposed to 0 (control), 0.1, 0.3, 0.8, and 2.4mg/L of ZnO-NPs under a flow-through exposure system. Fish were sampled at 0, 4, 8, and 12 weeks to test for zinc in the test water and blood, and biochemistry analysis; further, they were sampled at 12 weeks to observe ultrastructural changes in the liver, kidney, and gill. In the organic serum, changes in the glutamic pyruvic transaminase/alanine aminotransferase (GPT/ALT) and glutamic oxaloacetic transaminase/aspartate aminotransferase (GOT/AST) levels were significant, but changes in the lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) levels were not significantly different across all exposure periods. In the inorganic serum, the magnesium (Mg), inorganic phosphorus (IP), sodium (Na(+)), and chloride (Cl(-)) levels were significantly different in the exposure group and across exposure periods. However, calcium (Ca) and potassium (K(+)) levels were not significantly different. In the enzyme serum, the glucose (GLU) level significantly increased for the highest exposure group, but the total cholesterol (TCHO), triglyceride (Tg), and total protein (TP) levels were not significantly different during the exposure period. Ultrastructural changes in the liver induced changes in the black granules (of various sizes) in the lysosomes, indistinct nucleus membrane, and non-spherical nucleus. In the kidney, some mild changes were observed in the size and number of the lysosomes in the renal tubule. Desquamation and hypertrophy of pavement epithelial cells and vacuolation in the cytoplasm of the chloride cells were observed in the gill. Nanoparticles were also observed in the red blood cells, cytoplasm of all tissues, and glomerulus of the kidney. The observed changes in the serum and tissues may provide useful information regarding environmental conditions and risk assessments of aquatic organisms.

Stepwise Embryonic Toxicity of Silver Nanoparticles on Oryzias latipes

The developmental toxicity of silver nanoparticles (AgNPs) was investigated following exposure of Oryzias latipes (medaka) embryos to 0.1−1 mg/L of homogeneously dispersed AgNPs for 14 days. During this period, developmental endpoints, including lethality, heart rate, and hatching rate, were evaluated by microscopy for different stages of medaka embryonic development. To compare toxic sensitivity, acute adult toxicity was assessed. There was no difference in acute lethal toxicity between embryo and adult medaka. Interestingly, we found that the increase in stepwise toxicity was dependent on the developmental stage of the embryo. Lethal embryonic toxicity increased from exposure days 1 to 3 and exposure days 5 to 8, whereas there was no change from exposure days 3 to 5. In addition, 7 d exposure to 0.8 mg/L AgNPs resulted in significant heart beat retardation in medaka embryos. AgNPs also caused a dose-dependent decrease in the hatching rate and body length of larvae. These results indicate that AgNP exposure causes severe developmental toxicity to medaka embryos and that toxicity levels are enhanced at certain developmental stages, which should be taken into consideration in assessments of metallic NPs toxicity to embryos.

Stability of carboxyl-functionalized carbon black nanoparticles: the role of solution chemistry and humic acid

Carboxyl-functionalized carbon black nanoparticles (CB-NPs) are widely used in various industries. Studies on the dispersion and aggregation of nanomaterials in the aquatic environment are being actively conducted these days. In this study, the aggregation and sedimentation of carboxyl-functionalized CB-NPs were investigated according to the changes in the solution chemistry (0.1–10 mM NaCl and 0.01–1 mM CaCl2) and in the presence/absence of natural organic matter (1 and 5 mg L−1 humic acid) in the aquatic environment. Overall, humic acid was found to have the greatest effect on the stability of CB-NPs under the aquatic conditions investigated. Specifically, the sedimentation caused by CB-NP aggregation was more actively observed in NaCl than in CaCl2. With the increase in the ionic strength of the NaCl solution, the aggregation rate of CB-NPs also increased, whereas in the CaCl2 solution, the CB-NPs suspension stability was almost insensitive to the ionic strength. The reason was that the divalent cation Ca2+ was specifically adsorbed onto CB-NPs in the CaCl2 solution to reverse the negative CB-NP zeta potential, and increase the electrostatic repulsive force between CB-NPs. In the presence of humic acid in the NaCl and CaCl2 solutions, stability improved in the whole ionic strength range. A comparison of the classical Derjaguin–Landau–Verwey–Overbeek (DLVO) theory with the modified DLVO theory considering the steric force revealed that the enhanced stability of a CB-NP suspension in the presence of humic acid is attributed to a steric repulsive force as well as a stronger electrostatic repulsive force caused by humic acid adsorption.

Transport of carboxyl-functionalized carbon black nanoparticles in saturated porous media: Column experiments and model analyses

The aim of this study was to investigate the transport behavior of carboxyl-functionalized carbon black nanoparticles (CBNPs) in porous media including quartz sand, iron oxide-coated sand (IOCS), and aluminum oxide-coated sand (AOCS). Two sets of column experiments were performed under saturated flow conditions for potassium chloride (KCl), a conservative tracer, and CBNPs. Breakthrough curves were analyzed to obtain mass recovery and one-dimensional transport model parameters. The first set of experiments was conducted to examine the effects of metal (Fe, Al) oxides and flow rate (0.25 and 0.5 mL min(-1)) on the transport of CBNPs suspended in deionized water. The results showed that the mass recovery of CBNPs in quartz sand (flow rate=0.5 mL min(-1)) was 83.1%, whereas no breakthrough of CBNPs (mass recovery=0%) was observed in IOCS and AOCS at the same flow rate, indicating that metal (Fe, Al) oxides can play a significant role in the attachment of CBNPs to porous media. In addition, the mass recovery of CBNPs in quartz sand decreased to 76.1% as the flow rate decreased to 0.25 mL min(-1). Interaction energy profiles for CBNP-porous media were calculated using DLVO theory for sphere-plate geometry, demonstrating that the interaction energy for CBNP-quartz sand was repulsive, whereas the interaction energies for CBNP-IOCS and CBNP-AOCS were attractive with no energy barriers. The second set of experiments was conducted in quartz sand to observe the effect of ionic strength (NaCl=0.1 and 1.0mM; CaCl2=0.01 and 0.1mM) and pH (pH=4.5 and 5.4) on the transport of CBNPs suspended in electrolyte. The results showed that the mass recoveries of CBNPs in NaCl=0.1 and 1.0mM were 65.3 and 6.4%, respectively. The mass recoveries of CBNPs in CaCl2=0.01 and 0.1mM were 81.6 and 6.3%, respectively. These results demonstrated that CBNP attachment to quartz sand can be enhanced by increasing the electrolyte concentration. Interaction energy profiles demonstrated that the interaction energy profile for CBNP-quartz sand was compressed and that the energy barrier decreased as the electrolyte concentration increased. Furthermore, the mass recovery of CBNPs in the presence of divalent ions (CaCl2=0.1 mM) was far lower than that in the presence of monovalent ions (NaCl=0.1 mM), demonstrating a much stronger effect of Ca(2+) than Na(+) on CBNP transport. Mass recovery of CBNPs at pH 4.5 was 55.6%, which was lower than that (83.1%) at pH 5.4, indicating that CBNP attachment to quartz sand can be enhanced by decreasing the pH. The sticking efficiencies (α) calculated from the mass recovery by colloid filtration theory were in the range from 2.1×10(-2) to 4.5×10(-1), which were far greater than the values (2.56×10(-6)-3.33×10(-2)) of theoretical sticking efficiencies (αtheory) calculated from the DLVO energy by the Maxwell model.

Effects of ionization on the toxicity of silver nanoparticles to Japanese medaka (Oryzias latipes) embryos

Increase in the use of manufactured nanomaterials (NMs) has led to concerns about the environmental impacts. Especially, hazard of metal-based NMs is more severe due to ions released from surface by water quality parameters and physicochemical properties after entering into the water environment. However, little is known about the effects of ionization on the toxicity of metal-based NMs in the water environment. To address this question, we prepared the suspensions of silver nanoparticles (AgNP) at 25 μg L−1 containing different concentrations of Ag+ (5, 10, 20, 45, and 75% Ag+ to total Ag), and evaluated their toxicity to Japanese medaka (Oryzias latipes) embryos. Higher Ag+ ratios in the AgNP suspension, suggesting the lower number of particles, led to the higher adverse effects on embryos and sac-fries. In addition, histopathology analysis revealed that AgNPs penetrated through chorion of eggs and skin membrane, and were distributed into the tissues. The results imply that the ionization could decrease the toxicity of metal-based NMs in the water environment.

Comparison of Real Time Nanoparticle Monitoring Instruments in the Workplaces

Background Relationships among portable scanning mobility particle sizer (P-SMPS), condensation particle counter (CPC), and surface area monitor (SAM), which are different metric measurement devices, were investigated, and two widely used research grade (RG)-SMPSs were compared to harmonize the measurement protocols. Methods Pearson correlation analysis was performed to compare the relation between P-SMPS, CPC, and SAM and two common RG-SMPS. Results For laboratory and engineered nanoparticle (ENP) workplaces, correlation among devices showed good relationships. Correlation among devices was fair in unintended nanoparticle (UNP)-emitting workplaces. This is partly explained by the fact that shape of particles was not spherical, although calibration of sampling instruments was performed using spherical particles and the concentration was very high at the UNP workplaces to allow them to aggregate more easily. Chain-like particles were found by scanning electron microscope in UNP workplaces. The CPC or SAM could be used as an alternative instrument instead of SMPS at the ENP-handling workplaces. At the UNP workplaces, where concentration is high, real-time instruments should be used with caution. There are significant differences between the two SMPSs tested. TSI SMPS showed about 20% higher concentration than the Grimm SMPS in all workplaces. Conclusions For nanoparticle measurement, CPC and SAM might be useful to find source of emission at laboratory and ENP workplaces instead of P-SMPS in the first stage. An SMPS is required to measure with high accuracy. Caution is necessary when comparing data from different nanoparticle measurement devices and RG-SMPSs.

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.

Analysis of gold and silver nanoparticles internalized by zebrafish (Danio rerio) using single particle-inductively coupled plasma-mass spectrometry

With the increase in the application of nano-consumer products containing engineered nanoparticles (NPs), the unintended environmental exposure to NPs has been inevitable. Because of the bioaccumulation of NPs, concern about their potential cytotoxicity to aquatic organisms is also growing. Although measuring tools for analyzing particle size and/or concentration of NPs in intracellular uptake of tissues have been well developed, a simultaneous analysis of the two characteristics is difficult. The objective of this study was to use single particle-inductively coupled plasma-mass spectrometry (sp-ICP-MS) to measure the bioaccumulation and particle size changes of NPs exposed to zebrafish (Danio rerio) for 7 days. The uptake of NPs in the liver, intestine, and gill tissues was confirmed by electron microscopic (EM) analysis. However, the primary particle size of NPs in tissues could not be determined by the EM analysis. Therefore, sp-ICP-MS coupled with alkaline digestion was used for the easy extraction and immediate analysis of NPs from tissues. Zebrafish were exposed to four NPs (30 and 80 nm gold/silver NPs; AuNPs/AgNPs). Uptake amounts of AgNPs in the liver and intestine were significantly higher than those of AuNPs. Although larger NPs were finally accumulated in the liver and intestine tissues, most of the smaller NPs were filtered in the gills. The sp-ICP-MS method coupled with alkaline digestion enabled the accurate analysis of size, size distribution, and mass concentration of NPs in an aquatic organism.