Liver toxicity of multiwall carbon nanotubes in rats

Multiwall carbon nanotubes nowadays have multiple uses in the field of drug and gene delivery and other biological fields, and it is necessary to study their potential toxicity on organisms due to unique properties of these nanostructures. This study was conducted to determine the toxicity of multi-wall carbon nanotubes functionalized with carboxylic groups on the function and structure of the rats liver tissue. In this experimental study, 50 mature female Wistar Rats were randomly allocated into five groups including the control group of normal saline and Tween and treatment groups 2.5, 5, 10, 20 mg/kg/bw concentrations of multi-wall carbon nanotubes functionalized with carboxylic group with diameter less than 8 nm and length 30 micrometers that was received in 8 steps, intraperitoneally. Blood sampling was performed in two steps (The first stage was one day after the last injection and the second stage was 20 days after the last injection). The level of activity of the aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) enzymes and the amount of malondialdehyde were measured in serum. By preparing the tissue sections of the liver, a number of rats in each group (after 20 days from the last injection) with hematoxylin-eosin staining, the tissue structure of the liver was examined by optical microscopy. Animals were weighed before and after treatment. In the first stage, only the mean of AST activity at 5 mg/kg/bw concentration was significantly increased (P<0.05). In the second stage, ALP activity was significantly reduced (P<0.05) in all doses higher than 2.5 mg/kg/bw and the activity of AST and ALT in doses of 5 and 10 mg/kg/bw was significantly reduced (P<0.05) and in the dose of 2.5 mg/kg/bw was significantly increased (P<0.05). Histologic studies revealed disturbances such as degeneration of the vein wall of the lobular center, degeneration of the nucleus and hepatocyte lysis with severe atrophy, irregularity and dilatation of the sinusoids and accumulation of inflammatory cells in the treatment groups in dose-dependent manner. Based on the above findings the most disturbances were related to the 20 mg/kg/bw concentration. It seems that multi-wall carbon nanotubes functionalized with carboxylic group, even in small amounts (2.5 and 5 mg/kg/bw) after 20 days, are toxic on the liver and cause liver tissue and function impairment.