Retinopathy Induced by Zinc Oxide Nanoparticles in Rats Assessed by Micro-computed Tomography and Histopathology.

Nanotechnology has advanced at an extremely rapid pace over the past several years in numerous fields of research. However, the uptake of nanoparticles (NPs) into the body after administration through various routes may pose a risk to human health. In this study, we investigated the potential ocular toxicity of 20-nm, negatively- charged zinc oxide (ZnO) NPs in rats using micro-computed tomography (micro-CT) and histopathological assessment. Animals were divided into four groups as control group, ZnO NPs treatment group (500 mg/kg/day), control recovery group, and ZnO NPs treatment and recovery group. Ocular samples were prepared from animals treated for 90 days (10 males and 10 females, respectively) and from recovery animals (5 males and 5 females, respectively) sacrificed at 14 days after final treatment and were compared to age-matched control animals. Micro-CT analyses represented the deposition and distribution of foreign materials in the eyes of rats treated with ZnO NPs, whereas control animals showed no such findings. X-ray fluorescence spectrometry and energy dispersive spectrometry showed the intraocular foreign materials as zinc in treated rats, whereas control animals showed no zinc signal. Histopathological examination revealed the retinopathy in the eyes of rats treated with ZnO NPs. Neuronal nuclei expression was decreased in neurons of the ganglion cell layer of animals treated with ZnO NPs compared to the control group. Taken together, treatment with 20-nm, negatively-charged ZnO NPs increased retinopathy, associated with local distribution of them in ocular lesions.

Organization of research team for nano-associated safety assessment in effort to study nanotoxicology of zinc oxide and silica nanoparticles.

Currently, products made with nanomaterials are used widely, especially in biology, bio-technologies, and medical areas. However, limited investigations on potential toxicities of nanomaterials are available. Hence, diverse and systemic toxicological data with new methods for nanomaterials are needed. In order to investigate the nanotoxicology of nanoparticles (NPs), the Research Team for Nano-Associated Safety Assessment (RT-NASA) was organized in three parts and launched. Each part focused on different contents of research directions: investigators in part I were responsible for the efficient management and international cooperation on nano-safety studies; investigators in part II performed the toxicity evaluations on target organs such as assessment of genotoxicity, immunotoxicity, or skin penetration; and investigators in part III evaluated the toxicokinetics of NPs with newly developed techniques for toxicokinetic analyses and methods for estimating nanotoxicity. The RT-NASA study was carried out in six steps: need assessment, physicochemical property, toxicity evaluation, toxicokinetics, peer review, and risk communication. During the need assessment step, consumer responses were analyzed based on sex, age, education level, and household income. Different sizes of zinc oxide and silica NPs were purchased and coated with citrate, L-serine, and L-arginine in order to modify surface charges (eight different NPs), and each of the NPs were characterized by various techniques, for example, zeta potentials, scanning electron microscopy, and transmission electron microscopy. Evaluation of the "no observed adverse effect level" and systemic toxicities of all NPs were performed by thorough evaluation steps and the toxicokinetics step, which included in vivo studies with zinc oxide and silica NPs. A peer review committee was organized to evaluate and verify the reliability of toxicity tests, and the risk communication step was also needed to convey the current findings to academia, industry, and consumers. Several limitations were encountered in the RT-NASA project, and they are discussed for consideration for improvements in future studies.

Toxicity of colloidal silica nanoparticles administered orally for 90 days in rats.

This study was undertaken to investigate the potential toxicity and establish the no observed adverse effect level (NOAEL) and target organ(s) of negatively charged colloidal silica particles of different sizes, ie, SiO2 (EN20(-)) (20 nm) or SiO2 (EN100(-)) 2(100 nm), administered by gavage in Sprague-Dawley rats. After verification of the physicochemical properties of the SiO2 particles to be tested, a preliminary dose range-finding study and 90-day repeated dose study were conducted according to the Organisation for Economic Cooperation and Development test guideline. Based on the results of the 14-day dose range-finding study, a high dose was determined to be 2,000 mg/kg, and middle and low doses were set at 1,000 and 500 mg/kg, respectively. In the 90-day toxicity study, there were no animal deaths in relation to administration of SiO2 particles of either size. In addition, no treatment-related clinical changes or histopathological findings were observed in any of the experimental groups. Moreover, no difference in toxic effects from chronic exposure to SiO2 (EN20(-))(20 nm) or SiO2 (EN100(-)) (100 nm) was observed. The results of this study indicate that the NOAEL for SiO2 (EN20(-)) and SiO2 (EN100(-)) would most likely be 2,000 mg/kg, and no target organ was identified in rats of either sex.

A 90-day study of subchronic oral toxicity of 20 nm, negatively charged zinc oxide nanoparticles in Sprague Dawley rats.

PURPOSE: The widespread use of nanoparticles (NPs) in industrial and biomedical applications has prompted growing concern regarding their potential toxicity and impact on human health. This study therefore investigated the subchronic, systemic oral toxicity and no-observed-adverse-effect level (NOAEL) of 20 nm, negatively charged zinc oxide (ZnO(SM20(-))) NPs in Sprague Dawley rats for 90 days. METHODS: The high-dose NP level was set at 500 mg/kg of bodyweight, and the mid- and low-dose levels were set at 250 and 125 mg/kg, respectively. The rats were observed during a 14-day recovery period after the last NP administration for the persistence or reduction of any adverse effects. Toxicokinetic and distribution studies were also conducted to determine the systemic distribution of the NPs. RESULTS: No rats died during the test period. However, ZnO(SM20(-)) NPs (500 mg/kg) induced changes in the levels of anemia-related factors, prompted acinar cell apoptosis and ductular hyperplasia, stimulated periductular lymphoid cell infiltration and excessive salivation, and increased the numbers of regenerative acinar cells in the pancreas. In addition, stomach lesions were seen at 125, 250, and 500 mg/kg, and retinal atrophy was observed at 250 and 500 mg/kg. The Zn concentration was dose-dependently increased in the liver, kidney, intestines, and plasma, but not in other organs investigated. CONCLUSION: A ZnO(SM20(-)) NP NOAEL could not be established from the current results, but the lowest-observed-adverse-effect level was 125 mg/kg. Furthermore, the NPs were associated with a number of undesirable systemic actions. Thus, their use in humans must be approached with caution.

Toxicity of 100 nm zinc oxide nanoparticles: a report of 90-day repeated oral administration in Sprague Dawley rats.

Nanoparticles (NPs) are used commercially in health and fitness fields, but information about the toxicity and mechanisms underlying the toxic effects of NPs is still very limited. The aim of this study is to investigate the toxic effect(s) of 100 nm negatively (ZnO(AE100[-])) or positively (ZnO(AE100[+])) charged zinc oxide (ZnO) NPs administered by gavage in Sprague Dawley rats, to establish a no observed adverse effect level, and to identify target organ(s). After verification of the primary particle size, morphology, hydrodynamic size, and zeta potential of each test article, we performed a 90-day study according to Organisation for Economic Co-operation and Development test guideline 408. For the 90-day study, the high dose was set at 500 mg/kg and the middle and low doses were set at 125 mg/kg and 31.25 mg/kg, respectively. Both ZnO NPs had significant changes in hematological and blood biochemical analysis, which could correlate with anemia-related parameters, in the 500 mg/kg groups of both sexes. Histopathological examination showed significant adverse effects (by both test articles) in the stomach, pancreas, eye, and prostate gland tissues, but the particle charge did not affect the tendency or the degree of the lesions. We speculate that this inflammatory damage might result from continuous irritation caused by both test articles. Therefore, the target organs for both ZnO(AE100(-)) and ZnO(AE100(+)) are considered to be the stomach, pancreas, eye, and prostate gland. Also, the no observed adverse effect level for both test articles was identified as 31.25 mg/kg for both sexes, because the adverse effects were observed at all doses greater than 125 mg/kg.