Evaluation of 2-week repeated oral dose toxicity of 100 nm zinc oxide nanoparticles in rats

The aim of this study was to verify subacute oral dose toxicity of positively charged 100 nm zinc oxide (ZnO(AE100[+])) nanoparticles (NPs) in Sprague-Dawley rats. ZnO(AE100[+]) NPs were administered to rats of each sex by gavage at 0, 500, 1,000, and 2,000 mg/kg/day for 14 days. During the study period, clinical signs, mortality, body weight, food consumption, hematology, serum biochemistry, gross pathology, organ weight, and histopathology were examined. Increased mortality and clinical signs, decreased body weight, feed consumption, hemoglobin (HB), hematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), platelet (PT), and lymphocyte (LYM) and increased white blood cells (WBCs), neutrophils (NEUs), alkaline phosphatase (ALP), and histopathological alterations in the spleen, stomach, and pancreas were observed at 2,000 mg/kg/day. Increased clinical signs, decreased body weight, feed consumption, HB, HCT, MCV, MCH, MCHC, and LYM and increased WBCs, NEUs, ALP, and histopathological alterations in the spleen, stomach, and pancreas were seen at 1,000 mg/kg/day. Increased clinical signs, decreased MCV and MCH and increased histopathological alterations in the stomach and pancreas were found at 500 mg/kg/day. These results suggest that the target organs were the spleen, stomach, and pancreas in rats. The no-observed-adverse-effect level was <500 mg/kg for both sexes.