Journal of Pure and Applied MicrobiologyVol. 7 No. Special Edition Nov. 2013

Ecotoxicity of Ag-Nanoparticles to Microalgae

Amal A. Hazani1, Mohamed M. Ibrahim2,3*, Ibrahim A. Arif3, Afaf I. Shehata1, Gehan EL-Gaaly1, Mohamed Daoud4, Dalia Fouad4, Humaira Rizwana1 and Nadine Moubayed1

1Botany and Microbiology Department, Science College, King Saud University, P.O. Box, 22452, Riyadh, 11495 Riyadh, Saudi Arabia. 2Alexandria University, Faculty of Science, Botany and Microbiology Department, P. O. Box 21511 Alexandria, Egypt. 3Prince Sultan Research Chair for Environment & WildlifeScience College, King Saud University, Riyadh, Botany and Microbiology Department, P.O. Box, 2455, Riyadh, 11451 Riyadh, Saudi Arabia. 4Department of Biochemistry, College of Science, king Saud University, P.O. Box 2455, Riyadh 11451 Riyadh, Saudi Arabia.

Received on 12 August 2013 and accepted on 15 October 2013

ABSTRACT

Increasing application of nanotechnology highlights the need to clarify and understand nanotoxicity. In this work, the sub-acute toxicity of silver nanoparticles (Ag-NPs) to fresh water microalga Chlorella vulgaris and marine microalga Dunaliella tertiolecta were assessed. To induce Ag-NPs effect we exposed both algae to various concentrations of Ag-NPs (0 - 200 mg/L). Cellular viability and reactive oxygen species (ROS) formation were determined to evaluate the toxic effect of Ag-NPs on algal growth. Superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities and lipid peroxidation (MDA) levels in algal cells were varied with concentration of Ag-NPs suspensions and exposure time (up to 8 d). As a result, 100 and 200 mg/L Ag-NPs caused statistically significant decrease in cell viability, as well as, SOD, CAT and POD activities and significant increase in ROS formation and MDA levels in tissues (P < 0.05), suggesting that the algal cells exposed to these two concentrations of Ag-NPs suffered from the oxidative stress. The extent of depletion of antioxidant enzymes activities and the elevation of MDA in the D. tertiolecta was the greatest, indicating that D. tertiolecta might be the most susceptible to Ag-NPs exposure. These results indicated a potential risk from Ag-NPs released into the aqueous environment.

Keywords : Antioxidant, Chlorella, Dunaliella, Nanoparticles, oxidative stress.