Effect of adsorbed TiO2 nano-particles on aquatic organisms

Trabajo presentado en el 10th Iberian Congress on Environmental Contamination and Toxicology y el 7th Iberoamerican Congress on Environmental Contamination and Toxicology (CICTA 2015), celebrados en Vila Real (Portugal) del 14 al 17 de julio de 2015.

Titanium dioxide nanoparticles (TiO2 NPs) are widely used in multitude of applications and present a potential risk due to the release to the marine and freshwater systems.TiO2 NPs have been demonstrated to be toxic to unicellular algae, as they can be adsorbed or internalized by the cells. TiO2 NPs could induce toxicity to aquatic organisms through various mechanisms including physical damage, shading effect, oxidative stress and/or internalization. Surface interactions, such as adsorption of NPs oncells, are important toxicity mechanisms. One of the deleterious could be the increase of cell weight due to the adsorption of NPs, which would sink the floating cells out from the photic zone. On the other hand, different NPs can present different surface properties and aggregation states in the NP-cell suspensions, leading to different NP-cell heteroagglomerations. Water chemistry, such as pH and ionic strength (IS), can also influence the aggregation state of NPs and will thus influence the NPs-Cell.Since sizes of both microorganism cells and NPs aggregates are within the scale of colloids, the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory can be applied to analyze the colloidal behavior of NPs and cells in water. In this study, different freshwater and seawater species of microalgae were chosen in order to investigate interactions between algal cells and TiO2 NPs and TiO2 bulk, as well assedimentation rate of NPs, exposed and non exposed,cells in the water column. This is the first study specifically designed in order to check the NP-cell heteroagglomeration and cells sedimentation in water systems. Our findings show new light on bio-nano interaction.

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