Mansour Almansour,1 Saud Alarifi,1 Bashir Jarrar21Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia; 2Department of Biological Sciences, College of Science, Jerash University, Jerash, JordanBackground: Silicon dioxide (silica) nanoparticles (SDNPs) are widely used in nanotechnology and medicine, but these nanomaterials may carry a high risk for human health while little is known about their toxicity. Methods: We investigated the alterations in morphometry, biochemistry, hematology, histology of liver tissue and gene expression of drug-metabolizing enzymes induced by 10-nm SDNPs. Healthy male Wistar albino rats were exposed to 20, 35 and 50 repeated injections of SDNPs (2mg/kg body weight). Whole blood, serum and plasma samples were used for hematological and biochemical analyses, whereas liver biopsies were processed for histopathological and gene expression alterations. Results: In comparison with control rats, exposure to SDNPs lowered the body weight gain and liver index and increased the counts of white blood cells and platelets, but lowered the platelet larger cell ratio and plateletcrit. Levels of alkaline phosphatase, lactate dehydrogenase, low-density lipids, procalcitonin, aspartate aminotransferase and alanine aminotransferase, as well as potassium, phosphorus and iron concentrations, were increased. Histopathology revealed that SDNPs could induce hydropic degeneration, sinusoidal dilatation, hyperplasia of Kupffer cells, karyopyknosis and infiltration of inflammatory cells in the liver. SDNPs reduced the expression of 12 genes of drug-metabolizing enzymes significantly (p
