Toxicity of titanium nano-oxide nanoparticles (TiO2) on the pacific oyster, Crassostrea gigas: immunity and antioxidant defence

Abstract

In this study, the toxicity of titanium nano-oxide nanoparticles (TiO2) was examined on the immunity and antioxidant system of Pacific oyster, Crassostrea gigas. The oysters were collected from the intertidal areas of the shores of Imam Khomeini Port in the northwest of the Persian Gulf near the Khouzestan Petrochemical Complex (KPCC). The oysters were transferred to lab, acclimatized to lab conditions 10 days and then exposed to different concentrations (0, 5, 10 and 15 µg/l) of TiO2 for 14 days. After exposure period, the digestive gland and hemolymph were sampled to determine the activity of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx)] and immune parameters (total counts of homocytes, phagocytosis) respectively. Exposure to TiO2 significantly decreased the total counts of homocytes and phagocytosis activity compared to control, especially in exposure concentrations more than 10 µg/l (p < 0.01). The SOD and CAT activities elevated significantly in response to 5 µg/l TiO2 (p < 0.01). While, the high concentrations of TiO2 (10 and 15 µg/l) significantly decreased the activity of all antioxidant enzymes (p < 0.01). The activity of GPx showed significant decreased in the oysters exposed to 10 and 15 µg/l TiO2 compared to control (p < 0.01). The MDA levels showed significant increases in oysters exposed to TiO2 compared to control (p < 0.01). In conclusion, this study reveals that the environmentally relevant concentrations of TiO2 could reduce the immunity and antioxidant defence in the Pacific oyster. Therefore, special attentions should be paid to eliminate or minimize this contaminant in the coastal areas around the KPCC.