Serum proteins prevent aggregation of Fe₂O₃ and ZnO nanoparticles

Abstract

Aggregation of metal oxide nanoparticles in aqueous media complicates interpretation of in vitro studies of nanoparticle–cell interactions. We used dynamic light scattering to investigate the aggregation dynamics of iron oxide and zinc oxide nanoparticles. Our results show that iron oxide particles aggregate more readily than zinc oxide particles. Pretreatment with serum stabilises iron oxide and zinc oxide nanoparticles against aggregation. Serum-treated iron oxide is stable only in pure water, while zinc oxide is stable in water or cell culture media. These findings, combined with zeta potential measurements and quantification of proteins adsorbed on particle surface, suggest that serum stabilisation of iron oxide particles occurs primarily through protein adsorption and resulting net surface charge. Zinc oxide stabilisation, however, also involves steric hindrance of particle aggregation. Fluid shear at levels used in flow experiments breaks up iron oxide particle aggregates. These results enhance our understanding of nanoparticle aggregation and its consequences for research on the biological effects of nanomaterials.

Keywords::

• Metal oxide nanoparticles
• particle aggregation
• particle aging
• dynamic light scattering
• zeta potential
• fluid shear

Acknowledgements

We are grateful to Dr. Marjorie Longo (Department of Chemical Engineering and Materials Science, UC Davis) for the use of particle sizing equipment, Dr. Thomas Young (Civil and Environmental Engineering, UC Davis) for the use of BIC ZetaPlus instrument and Will Bernt (Particle Characterisation Laboratories, Novato, CA, USA) for training and technical advice. Although the research described in the article has been funded in part by the United States Environmental Protection Agency through grant RD-83241401-0 to the University of California, Davis, it has not been subject to the Agency's required peer and policy review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred. This publication was made possible in part by grant number 5 P42 ES004699 from the National Institute of Environmental Health Sciences (NIEHS), NIH and the contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS, NIH. This work was funded in part by an endowment in Cardiovascular Cellular Engineering from the AXA Research Fund.