Ecotoxicity study of titania (TiO2) NPs on two microalgae species: Scenedesmus sp. and Chlorella sp.

In view of their increasing commercial applications metal oxide NPs like titania have elevated chances of entry to the environment. The ecotoxicity analyses are required to assess their environmental risks. The present work aims to demonstrate the effect of titania NPs on microalgae isolated from freshwater environment (Scenedesmus sp. and Chlorella sp.). The growth inhibitory effect of titania NPs was observed for both the species (72 h EC50 value, 16.12 mg/L for Chlorella sp.; 21.2 mg/L for Scenedesmus sp.). Bulk micron-sized titania also showed toxicity though to a lesser extent (72 h EC50 value, 35.50 mg/L for Chlorella sp.; 44.40 mg/L for Scenedesmus sp.). A concentration dependent decrease in chlorophyll content was observed in the treated cells compared to the untreated ones, more effect being notable in case of NPs. Preliminary results based on FT-IR studies and microscopic images suggest interaction of the NPs with the cell surface.