Jayoung Jeong

Pharmacokinetics, tissue distribution, and excretion of zinc oxide nanoparticles

Background This study explored the pharmacokinetics, tissue distribution, and excretion profile of zinc oxide (ZnO) nanoparticles with respect to their particle size in rats. Methods Two ZnO nanoparticles of different size (20 nm and 70 nm) were orally administered to male and female rats, respectively. The area under the plasma concentration-time curve, tissue distribution, excretion, and the fate of the nanoparticles in organs were analyzed. Results The plasma zinc concentration of both sizes of ZnO nanoparticles increased during the 24 hours after administration in a dose-dependent manner. They were mainly distributed to organs such as the liver, lung, and kidney within 72 hours without any significant difference being found according to particle size or rat gender. Elimination kinetics showed that a small amount of ZnO nanoparticles was excreted via the urine, while most of nanoparticles were excreted via the feces. Transmission electron microscopy and x-ray absorption spectroscopy studies in the tissues showed no noticeable ZnO nanoparticles, while new Zn-S bonds were observed in tissues. Conclusion ZnO nanoparticles of different size were not easily absorbed into the bloodstream via the gastrointestinal tract after a single oral dose. The liver, lung, and kidney could be possible target organs for accumulation and toxicity of ZnO nanoparticles was independent of particle size or gender. ZnO nanoparticles appear to be absorbed in the organs in an ionic form rather than in a particulate form due to newly formed Zn-S bonds. The nanoparticles were mainly excreted via the feces, and smaller particles were cleared more rapidly than the larger ones. ZnO nanoparticles at a concentration below 300 mg/kg were distributed in tissues and excreted within 24 hours. These findings provide crucial information on possible acute and chronic toxicity of ZnO nanoparticles in potential target organs.

Effect of the size and surface charge of silica nanoparticles on cutaneous toxicity

Silica nanoparticles (NPs) are widely applied in many fields, such as chemical industry, medicine, cosmetics, and agriculture. However, the hazardous effects of silica NPs exposure are not completely understood. In this study, the two different sizes (20 nm and 100 nm) and different charges (negatively charged [NC] and weakly negatively charged [WNC]) of silica NPs were used. The present study investigated the cytotoxicity and reactive oxygen species (ROS) generation of silica NPs on keratinocytes. The phototoxicity test of silica NPs was performed on skin fibroblast cells. In addition, skin irritation and skin sensitization of silica NPs were studied on HSEM and mouse skin, respectively. The cell viability of NC 20 nm silica NPs was decreased. However, there are no cytotoxicity for NC 100 nm silica NPs and WNC silica NPs (20 and 100 nm). The results for silica NPs-induced ROS generation are consistent with the cytotoxicity test by silica NPs. Further, NC and WNC silica NPs induced no phototoxicity, acute cutaneous irritation, or skin sensitization. These results suggested that silica NPs-induced ROS generation was the determinant of cytotoxicity. This study showed that the smaller size (20 nm) of silica NPs had more toxicity than the larger size (100 nm) of silica NPs for NC silica NPs. Moreover, we observed an effect of surface charge in cytotoxicity and ROS generation, by showing that the NC silica NPs (20 nm) had more toxic than the WNC silica NPs (20 nm). These findings suggested that the surface charge of silica NPs might be the important parameter for silica NPs-induced toxicity. Further study is needed to assess the effect of surface modification of nanotoxicity.

Predictive value of in vitro assays depends on the mechanism of toxicity of metal oxide nanoparticles.

BackgroundHazard identification for risk assessment of nanoparticles (NPs) is mainly composed of in vitro cell-based assays and in vivo animal experimentation. The rapidly increasing number and functionalizations of NPs makes in vivo toxicity tests undesirable on both ethical and financial grounds, creating an urgent need for development of in vitro cell-based assays that accurately predict in vivo toxicity and facilitate safe nanotechnology.MethodsIn this study, we used 9 different NPs (CeO2, TiO2, carbon black, SiO2, NiO, Co3O4, Cr2O3, CuO, and ZnO). As an in vivo toxicity endpoint, the acute lung inflammogenicity in a rat instillation model was compared with the in vitro toxicity endpoints comprising cytotoxicity, pro-inflammatory cytokine expression, or haemolytic potential. For in vitro assays, 8 different cell-based assays were used including epithelial cells, monocytic/macrophage cells, human erythrocytes, and combined culture.ResultsZnO and CuO NPs acting via soluble toxic ions showed positive results in most of assays and were consistent with the lung inflammation data. When compared in in vitro assays at the same surface area dose (30xa0cm2/mL), NPs that were low solubility and therefore acting via surface reactivity had no convincing activity, except for CeO2 NP. Cytotoxicity in differentiated peripheral blood mononuclear cells was the most accurate showing 89% accuracy and 11% false negativity in predicting acute lung inflammogenicity. However, the haemolysis assay showed 100% consistency with the lung inflammation if any dose, having statistical significance was considered positivity. Other cell-based in vitro assays showed a poorer correlation with in vivo inflammogenicity.ConclusionsBased on the toxicity mechanisms of NPs, two different approaches can be applied for prediction of in vivo lung inflammogenicity. Most in vitro assays were good at detecting NPs that act via soluble ions (i.e., ZnO and CuO NP). However, in vitro assays were limited in detecting NPs acting via surface reactivity as their mechanism of toxicity, except for the haemolysis assay.

Optical imaging to trace near infrared fluorescent zinc oxide nanoparticles following oral exposure

Background Understanding how nanomaterials are distributed in the body after exposure is important for assessing whether they are safe. In this study, we investigated the behavior and accumulation of nanoscaled and submicron-scaled zinc oxide (ZnO) particles in the body using optical imaging following oral exposure. Methods To trace these nanoparticles in the body, ZnO nanoparticles were conjugated with a monoreactive hydroxysuccinimide ester of Cy5.5 (Cy5.5-NHS), and the conjugation-stabilizing effect of Cy5.5 on the nanoparticles was evaluated in simulated gastric fluid (pH 1.2) for 7 hours. To compare the distribution of Cy5.5-NHS and Cy5.5-conjugated ZnO nanoparticles, Cy5.5-NHS 0.5 mg/kg and Cy5.5-conjugated ZnO nanoparticles 250 mg/kg were administered orally to healthy rats. We collected blood from the rats at predesignated time points for 7 hours after administration, and optical imaging studies were performed at 1, 2, 3, 5, and 7 hours after dosing. To investigate the extent of nanoparticle accumulation in the organs and tissues, the mice were sacrificed at 23 hours after administration, and the organs were removed and imaged. Results Cy5.5-conjugated ZnO nanoparticles were stable in simulated gastric fluid for 7 hours. The signal intensity of Cy5.5-NHS in blood was highest 3 hours after oral administration, and Cy5.5-conjugated ZnO nanoparticles showed the highest signal intensity in blood 5–7 hours after administration. In vivo optical images indicated that Cy5.5-NHS showed optical signals in the lung, liver, and gastrointestinal tract after oral administration, whereas Cy5.5-conjugated ZnO nanoparticles were seen only in the gastrointestinal tract. Seven hours following administration, biodistribution studies demonstrated that Cy5.5-NHS accumulated in the lung and liver, and Cy5.5-conjugated ZnO nanoparticles resulted in a strong signal in the kidney and liver. Different-sized ZnO nanoparticles showed dissimilar patterns of biodistribution in ex vivo optical images. Conclusion ZnO nanoparticles are absorbed into the tissues following oral exposure and their behavior can be monitored and evaluated using optical imaging.

Toxicity evaluation of inorganic nanoparticles: considerations and challenges

Toxicity evaluation of inorganic nanoparticles in cell lines and in whole animals has been extensively explored in recent years. However, conflicting results have been reported regarding size-dependent toxicity and biokinetics in vitro and in vivo, and thus, basic questions regarding whether nanoparticles, ranged from 1 to 100 nm in size, are comparatively more toxic than larger-sized particles remain unanswered. This may be closely associated with changes in physicochemical properties of nanoparticles in biological fluids. Understanding in vivo physiological barriers, biological fates, and absorption mechanism of nanoparticles upon exposure routes will be useful to predict their toxicity potential. This review will highlight the critical points to be considered in order to evaluate the toxicity of inorganic nanoparticles, and discuss the issues and challenges emerging in the field of nanotoxicology.

Lack of genotoxic potential of ZnO nanoparticles in in vitro and in vivo tests

The industrial application of nanotechnology, particularly using zinc oxide (ZnO), has grown rapidly, including products such as cosmetics, food, rubber, paints, and plastics. However, despite increasing population exposure to ZnO, its potential genotoxicity remains controversial. The biological effects of nanoparticles depend on their physicochemical properties. Preparations with well-defined physico-chemical properties and standardized test methods are required for assessing the genotoxicity of nanoparticles. In this study, we have evaluated the genotoxicity of four kinds of ZnO nanoparticles: 20nm and 70nm size, positively or negatively charged. Four different genotoxicity tests (bacterial mutagenicity assay, in vitro chromosomal aberration test, in vivo comet assay, and in vivo micronucleus test, were conducted, following Organization for Economic Cooperation and Development (OECD) test guidelines with good laboratory practice (GLP) procedures. No statistically significant differences from the solvent controls were observed. These results suggest that surface-modified ZnO nanoparticles do not induce genotoxicity in in vitro or in vivo test systems.

Tissue distribution and excretion kinetics of orally administered silica nanoparticles in rats

Purpose The effects of particle size on the tissue distribution and excretion kinetics of silica nanoparticles and their biological fates were investigated following a single oral administration to male and female rats. Methods Silica nanoparticles of two different sizes (20 nm and 100 nm) were orally administered to male and female rats, respectively. Tissue distribution kinetics, excretion profiles, and fates in tissues were analyzed using elemental analysis and transmission electron microscopy. Results The differently sized silica nanoparticles mainly distributed to kidneys and liver for 3 days post-administration and, to some extent, to lungs and spleen for 2 days post-administration, regardless of particle size or sex. Transmission electron microscopy and energy dispersive spectroscopy studies in tissues demonstrated almost intact particles in liver, but partially decomposed particles with an irregular morphology were found in kidneys, especially in rats that had been administered 20 nm nanoparticles. Size-dependent excretion kinetics were apparent and the smaller 20 nm particles were found to be more rapidly eliminated than the larger 100 nm particles. Elimination profiles showed 7%–8% of silica nanoparticles were excreted via urine, but most nanoparticles were excreted via feces, regardless of particle size or sex. Conclusion The kidneys, liver, lungs, and spleen were found to be the target organs of orally-administered silica nanoparticles in rats, and this organ distribution was not affected by particle size or animal sex. In vivo, silica nanoparticles were found to retain their particulate form, although more decomposition was observed in kidneys, especially for 20 nm particles. Urinary and fecal excretion pathways were determined to play roles in the elimination of silica nanoparticles, but 20 nm particles were secreted more rapidly, presumably because they are more easily decomposed. These findings will be of interest to those seeking to predict potential toxicological effects of silica nanoparticles on target organs.

Comparative toxicity of silicon dioxide, silver and iron oxide nanoparticles after repeated oral administration to rats.

Although silicon dioxide (SiO2), silver (Ag) and iron oxide (Fe2O3) nanoparticles are widely used in diverse applications from food to biomedicine, in vivo toxicities of these nanoparticles exposed via the oral route remain highly controversial. To examine the systemic toxicity of these nanoparticles, well‐dispersed nanoparticles were orally administered to Sprague–Dawley rats daily over a 13‐week period. Based on the results of an acute toxicity and a 14‐day repeated toxicity study, 975.9, 1030.5 and 1000 mg kg–1 were selected as the highest dose of the SiO2, Ag and Fe2O3 nanoparticles, respectively, for the 13‐week repeated oral toxicity study. The SiO2 and Fe2O3 nanoparticles did not induce dose‐related changes in a number of parameters associated with the systemic toxicity up to 975.9 and 1000 mg kg–1, respectively, whereas the Ag nanoparticles resulted in increases in serum alkaline phosphatase and calcium as well as lymphocyte infiltration in liver and kidney, raising the possibility of liver and kidney toxicity induced by the Ag nanoparticles. Compared with the SiO2 and Fe2O3 nanoparticles showing no systemic distribution in all tissues tested, the Ag concentration in sampled blood and organs in the Ag nanoparticle‐treated group significantly increased with a positive and/or dose‐related trend, meaning that the systemic toxicity of the Ag nanoparticles, including liver and kidney toxicity, might be explained by extensive systemic distribution of Ag originating from the Ag nanoparticles. Our current results suggest that further study is required to identify that Ag detected outside the gastrointestinal tract were indeed a nanoparticle form or ionized form. Copyright

Subchronic toxicity study of Coptidis Rhizoma in rats

ETHNOPHARMACOLOGICAL RELEVANCEnCoptidis Rhizoma (CR) is a medical herb from the family Ranunculacease that has been used to treat gastroenteritis, dysentery, diabetes mellitus, and severe skin diseases.nnnAIM OF THE STUDYnTo evaluate the no-observed-adverse-effect level (NOAEL) and the toxicity of CR, following repeat oral administration to rats for 13 weeks.nnnMATERIALS AND METHODSnCR was administered by oral gavage to groups of rats (n=10/group, each sex) at dose levels of 0 (control), 25, 74, 222, 667 or 2000 mg/kg/day 5 times per week for 13 weeks. Mortality, clinical signs, body weights, food consumption, hematology, serum chemistry, urinalysis, vaginal cytology and sperm morphology, organ weights, gross and histopathological findings were compared between control and CR groups.nnnRESULTSnUrinalysis showed a significant increase in N-acety1-β-glucosaminidase in males in the 2000 mg/kg/day group (P<0.01). However, no mortality or remarkable clinical signs were observed during this 13-week study. No adverse effects on body weight, food consumption, hematology, serum chemistry, organ weights, gross lesion, histopathology, vaginal cytology, sperm motility, or deformity were observed in the males or female rats treated with CR.nnnCONCLUSIONSnOn the basis of these results, the NOAEL of CR is determined to be 667 mg/kg/day for males and 2000 mg/kg/day for females.

Nickel oxide nanoparticles can recruit eosinophils in the lungs of rats by the direct release of intracellular eotaxin

BackgroundInstillation of highly soluble nanoparticles (NPs) into the lungs of rodents can cause acute eosinophilia without any previous sensitizations by the role of dissolved ions. However, whether gradually dissolving NPs can cause the same type of eosinophilia remains to be elucidated. We selected nickel oxide (NiO) as a gradually dissolving NP and evaluated the time course pulmonary inflammation pattern as well as its mechanisms.MethodsNiO NPs were intratracheally instilled into female Wistar rats at various concentrations (50, 100, and 200xa0cm2/rat) and the lung inflammation was evaluated at various time-points (1, 2, 3, and 4xa0days). As positive controls, NiCl2 and the ovalbumin-induced allergic airway inflammation model was applied. NiCl2 was instilled at 171.1xa0μg Ni/rat, which is equivalent nickel concentration of 200xa0cm2/rat of NiO NPs. Cytological analysis and biochemical analysis including lactate dehydrogenase (LDH), total protein, and pro-inflammatory cytokines were measured in bronchoalveolar lavage fluid (BALF). The levels of total immunoglobulin E (IgE) and anaphylatoxins (C3a and C5a) were measured in BALF and serum. The levels of eotaxin were measured in the alveolar macrophages and normal lung tissue before and after addition of cell lysis buffer to evaluate whether the direct lysis of cells can release intracellular eotaxin.ResultsNiO NPs produced acute neutrophilic inflammation throughout the study. However, eosinophils were recruited at 3 and 4xa0days post-instillation of NiO NPs and the magnitude and pattern of inflammation was similar with NiCl2 at 24xa0h post-instillation. The eosinophil recruitment by NiO NPs was not related with either the levels of total IgE or anaphylatoxins. The lysis of alveolar macrophages and normal lung tissue showed high levels of intracellular eotaxin and the levels of LDH showed positive correlation with the levels of eotaxin.ConclusionsInstillation of NiO NPs produced neutrophilia at 1 and 2xa0days after instillation, while the mixed type of neutrophilic and eosinophilic inflammation was produced at 3 and 4xa0days post-instillation, which was consistent with NiCl2. The mechanism of the eosinophilia involves the direct release of intracellular eotaxin due to the rupture of cells by the accumulated solubilized nickel ions in the phagolysosome.