Untangling the biological effects of cerium oxide nanoparticles: the role of surface valence states.
Cerium oxide nanoparticles (nanoceria; CNPs) have been found to have both pro-oxidant and anti-oxidant effects on different cell systems or organisms. In order to untangle the mechanisms which underlie the biological activity of nanoceria, we have studied the effect of five different CNPs on a model relevant aquatic microorganism. Neither shape, concentration, synthesis method, surface charge (ζ-potential), nor nominal size had any influence in the observed biological activity. The main driver of toxicity was found to be the percentage of surface content of Ce(3+) sites: CNP1 (58%) and CNP5 (40%) were found to be toxic whereas CNP2 (28%), CNP3 (36%) and CNP4 (26%) were found to be non-toxic. The colloidal stability and redox chemistry of the most and least toxic CNPs, CNP1 and CNP2, respectively, were modified by incubation with iron and phosphate buffers. Blocking surface Ce(3+) sites of the most toxic CNP, CNP1, with phosphate treatment reverted toxicity and stimulated growth. Colloidal destabilization with Fe treatment only increased toxicity of CNP1. The results of this study are relevant in the understanding of the main drivers of biological activity of nanoceria and to define global descriptors of engineered nanoparticles (ENPs) bioactivity which may be useful in safer-by-design strategies of nanomaterials.
Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049, Spain.
Gerardo
G
Pulido-Reyes
Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049, Spain.
Ismael
I
Rodea-Palomares
Advanced Material Processing Analysis Center and Nanoscience Technology Center, Materials Science and Eng, UCF College of Medicine, University of Central Florida, Florida 32826, United States.
Soumen
S
Das
Advanced Material Processing Analysis Center and Nanoscience Technology Center, Materials Science and Eng, UCF College of Medicine, University of Central Florida, Florida 32826, United States.
Tamil Selvan
TS
Sakthivel
Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049, Spain.
Francisco
F
Leganes
Departamento de Ingeniería Química, Universidad de Alcalá, E-28871, Alcalá de Henares, Madrid, Spain.
Roberto
R
Rosal
Advanced Material Processing Analysis Center and Nanoscience Technology Center, Materials Science and Eng, UCF College of Medicine, University of Central Florida, Florida 32826, United States.
Sudipta
S
Seal
Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049, Spain.
Francisca
F
Fernández-Piñas
D000975:Antioxidants / Q000009:adverse effects; D059001:Aquatic Organisms / Q000187:drug effects*; D002563:Cerium / Q000737:chemistry / Q000633:toxicity*; D053758:Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013499:Surface Properties / Q000187:drug effects
D000975:Antioxidants; D017382:Reactive Oxygen Species; D002563:Cerium; C030583:ceric oxide