The critical role of the dispersant agents in the preparation and ecotoxicity of nanomaterial suspensions

This work reports the role of different dispersants, namely, polyethylene glycol (PEG 200 2%), ethylene glycol 5%, ethanol 2%, dimethyl sulfoxide (DMSO 5%), and polyvinyl alcohol (PVA 5%) in the toxicity profile of several commercial nanomaterials (NM), such as hydrophilic and hydrophobic TiO 2 , hydrophilic SiO 2 , SiO 2 in aqueous suspension (aq), and ZnO towards the bioluminescent bacterium Aliivibrio fischeri . The majority of NM showed tendency to form agglomerates in the different dispersants. Although some particle agglomeration could be detected, DMSO at 5% was the best dispersant for hydrophobic TiO 2 NM while PVA at 5% was the most effective dispersant for the other types of NM. Average size was not the most relevant aspect accounting for their toxicity. A remarkable reduction in average size was followed by a decrease in NM toxicity, as demonstrated for SiO 2 aq. in PVA 5%. Contrarily, despite of high particle agglomeration, ZnO NM showed a higher toxicity to bacteria when compared with other tested NM. Independently of the average particle size or surface charge, the dispersant either enhanced the toxicity to bacteria or acted as physical barrier decreasing the NM harmful effect to A. fischeri .