Abstract
Abstract Objective Present study aims to evaluate oxidative stress-mediated toxicity mechanisms of nano-ZnO (N-ZnO) compared to ZnCl 2 and bulk-ZnO (M-ZnO), using cyanobacterium as a toxicity assessment tool. Methods Nostoc muscorum was used as a test organism and the experiments were performed in parallels after treated with 2–128 μM of N-ZnO, M-ZnO, and ZnCl 2 . Results Low concentrations of ZnCl 2 (2–8 μM) and N-ZnO (16–32 μM) led to a significant increase in the carotenoids, which could be ascribed to its role as an antioxidant, whereas higher concentrations were inhibitory to the photosynthetic pigments. Enhanced activities of superoxide dismutase (SOD), peroxidase (POD) and accelerated lipid peroxidation depicted significant accumulation of superoxide and peroxide radicals in N. muscorum exposed to N-ZnO and ZnCl 2 . The non-enzymatic antioxidants such as proline and total phenols also showed enhanced accumulations up to 16 and 64 μM of ZnCl 2 and N-ZnO treatment, respectively. Conclusion Our results for the very first time depicted the significant accumulation of stress biomarkers in N. muscorum in response to deleterious effects of oxidative stress caused by N-ZnO, ZnCl 2 , and M-ZnO. Present results revealed varying levels of toxicity of various forms of zinc, which decreased in an order of ZnCl 2 >N-ZnO>M-ZnO.