Oxidative stress responses to carboxylic acid functionalized single wall carbon nanotubes on the human intestinal cell line Caco-2.

Carbon nanotubes (CNT) are among the more promising nanomaterials due to their potential applications. In this sense, the adverse effects that CNT can induce are of concern. In particular, carboxylic acid functionalized single wall carbon nanotubes (COOH-SWCNT) have shown to reduce cell viability and induce morphological effects on the human intestinal cell line Caco-2, but little is known about the toxic mechanisms involved. The aim of the present study was to investigate the oxidative stress responses of this cell line after 24h exposure to COOH-SWCNT. Biomarkers assayed included lipid peroxidation (LPO), reactive oxygen species (ROS) generation, and enzymatic and non-enzymatic antioxidant defences. Results showed an increase in ROS from 100μg/mL reaching 5.2-fold the basal value at the highest concentration assayed. An induction of catalase, superoxide dismutase and glutathione peroxidase activities was also observed, meanwhile glutathione reductase showed a reduced activity at 1000μg/mL. Glutathione (GSH) levels also decreased (2.5-fold) at the highest level of exposure. Therefore, the antioxidant defences could not overwhelm the oxidative insult caused by COOH-SWCNT and LPO products increased in a concentration-dependent manner. We can conclude that oxidative stress plays a role in the pathogenicity induced by COOH-SWCNT on Caco-2 cells at the concentrations assayed.