title: CeO2NPs, toxic or protective to phytoplankton? Charge of nanoparticles and cell wall as factors which cause changes in cell complexity.
abstract: CeO2nanoparticles (CeO2NPs) are well-known for their catalytic properties and antioxidant potential. Recent uses in therapy are based on the Ce+3ions released by CeO2NPs. Reactions involving redox cycles between Ce+3and Ce+4oxidation stage seem to promote scavenging of reactive oxygen species (ROS), thus protecting cells from oxygen damage. However, the internalization of CeO2NPs and release of Ce+3could be responsible for a toxic effect on cells. The literature reports controversial results on the toxicity of CeO2NPs to phytoplankton. Therefore, we have tested the potential toxic effect of two CeO2NPs (with positive and negative zeta potential) and bulk CeO2(at 0.1, 1, 10, 100 and 200mg·L-1) on three species of microalgae from different environments: marine diatom (Phaeodactylum tricornutum), marine chlorophyte (Nannochloris atomus) and freshwater chlorophyte (Chlamydomonas reinhardtii) over 72h in batch cultures. Responses measured in the microalgae population are: growth, chlorophyll a, cell size, cell complexity, percentage of ROS, and percentage of cell membrane damage. Positive zeta potential CeO2NPs provoked greater cell complexity (up to 78, 172 and 23 times more cell complexity than in controls found for C. reinhardtii, P. tricornutum and N. atomus respectively) than negative zeta potential CeO2NPs. The SSC signal detected by flow cytometry measured increases of particles entering cells, and this is related to cell viability and levels of intracellular ROS (correlation between SSC and percentage of ROS of 0.72 and 0.97 found for C. reinhardtii and P. tricornutum). When increased cellular complexity over controls is between 2 and 6 times greater, CeO2(in bulk or nanoparticulate form) seems to protect against ROS. When increased cellular complexity is from 7 to 23 times greater, CeO2does not provoke toxic responses; however, when increased cellular complexity over controls is very high, from 61 to 172 times, increased ROS production and toxic responses are found. Results show that two factors, the charge of CeO2NPs and cell wall structure, constitute the primary barrier to the possible accumulation of CeO2NPs within phytoplankton cytosol.
authors.affiliation: Department of Ecology and Coastal Management, Institute of Marine Sciences of Andalusia (CSIC), Campus Río S. Pedro, 11510 Puerto Real, Cádiz, Spain. Electronic address: marta.sendra@icman.csic.es.
authors.forename: M
authors.initials: M
authors.lastname: Sendra
authors.affiliation: Department of Material Science, Metallurgical Engineering and Inorganic Chemistry, Faculty of Sciences, University of Cadiz, E-11510 Puerto Real, Cádiz, Spain.
authors.forename: P M
authors.initials: PM
authors.lastname: Yeste
authors.affiliation: Department of Ecology and Coastal Management, Institute of Marine Sciences of Andalusia (CSIC), Campus Río S. Pedro, 11510 Puerto Real, Cádiz, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Moreno-Garrido
authors.affiliation: Department of Material Science, Metallurgical Engineering and Inorganic Chemistry, Faculty of Sciences, University of Cadiz, E-11510 Puerto Real, Cádiz, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Gatica
authors.affiliation: Department of Ecology and Coastal Management, Institute of Marine Sciences of Andalusia (CSIC), Campus Río S. Pedro, 11510 Puerto Real, Cádiz, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Blasco
mesh_terms: D002473:Cell Wall / Q000648:ultrastructure; D002563:Cerium / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D010839:Phytoplankton / Q000187:drug effects*; D017382:Reactive Oxygen Species
chemical_list: D017382:Reactive Oxygen Species; D002563:Cerium; C030583:ceric oxide
keywords: Internal granularity; Microalgae; Nanoparticles; Zeta potential