title: Cytotoxicity of TiO₂ nanoparticles and their detoxification in a freshwater system.
abstract: In the current study, two aspects concerning (i) the cytotoxicity potential of TiO₂ nanoparticles (NPs) toward freshwater algal isolate Scenedesmus obliquus and (ii) the potential detoxification of NPs by the microalgae were assessed under light (UV-illumination) and dark conditions at low exposure levels (≤1 μg/mL), using sterile freshwater as the test medium. The statistically significant reduction in cell viability, increase in reactive oxygen species production and membrane permeability (light vs. dark) suggested photo-induced toxicity of TiO₂ NPs. The electron micrographs demonstrated adsorption of the NPs onto the cell surface and substantiated their internalization/uptake. The fluorescence micrographs and the confocal laser scanning (CLSM) images suggested the absence of a definite/intact nucleus in the light treated cells pointing toward the probable genotoxic effects of NPs. In a separate three cycle experiment, a continuous decrease in the cytotoxicity was observed, whereas, at the end of each cycle only fresh algae were added to the supernatant containing NPs from the previous cycle. The decreasing concentrations of the NPs in the subsequent cycles owing to agglomeration-sedimentation processes exacerbated by the algal interactions played a crucial role in the detoxification. In addition, the exo-polymeric substances produced by the cells could have rendered the available NPs less reactive, thereby, enhancing the detoxification effects.
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, India.
authors.forename: Swayamprava
authors.initials: S
authors.lastname: Dalai
authors.forename: Sunandan
authors.initials: S
authors.lastname: Pakrashi
authors.forename: M
authors.initials: M
authors.lastname: Joyce Nirmala
authors.forename: Apoorvi
authors.initials: A
authors.lastname: Chaudhri
authors.forename: N
authors.initials: N
authors.lastname: Chandrasekaran
authors.forename: A B
authors.initials: AB
authors.lastname: Mandal
authors.forename: Amitava
authors.initials: A
authors.lastname: Mukherjee
mesh_terms: D000327:Adsorption; D001673:Biodegradation, Environmental; D002452:Cell Count; D002463:Cell Membrane Permeability / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004785:Environmental Pollutants / Q000633:toxicity*; D005618:Fresh Water; D053768:Metal Nanoparticles / Q000633:toxicity* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D017382:Reactive Oxygen Species / Q000378:metabolism; D044444:Scenedesmus / Q000187:drug effects* / Q000648:ultrastructure; D013778:Tetrazolium Salts; D013844:Thiazoles; D014025:Titanium / Q000633:toxicity*; D018675:Toxicity Tests; D014466:Ultraviolet Rays
chemical_list: D004785:Environmental Pollutants; D017382:Reactive Oxygen Species; D013778:Tetrazolium Salts; D013844:Thiazoles; C009495:titanium dioxide; D014025:Titanium; C022616:thiazolyl blue