Adoption of in vitro systems and zebrafish embryos as alternative models for reducing rodent use in assessments of immunological and oxidative stress responses to nanomaterials

Abstract

Assessing the safety of engineered nanomaterials (NMs) is paramount to the responsible and sustainable development of nanotechnology, which provides huge societal benefits. Currently, there is no evidence that engineered NMs cause detrimental health effects in humans. However, investigation of NM toxicity using in vivo, in vitro, in chemico, and in silico models has demonstrated that some NMs stimulate oxidative stress and inflammation, which may lead to adverse health effects. Accordingly, investigation of these responses currently dominates NM safety assessments. There is a need to reduce reliance on rodent testing in nanotoxicology for ethical, financial and legislative reasons, and due to evidence that rodent models do not always predict the human response. We advocate that in vitro models and zebrafish embryos should have greater prominence in screening for NM safety, to better align nanotoxicology with the 3Rs principles. Zebrafish are accepted for use by regulatory agencies in chemical safety assessments (e.g. developmental biology) and there is growing acceptance of their use in biomedical research, providing strong foundations for their use in nanotoxicology. We suggest that investigation of the response of phagocytic cells (e.g. neutrophils, macrophages) in vitro should also form a key part of NM safety assessments, due to their prominent role in the first line of defense. The development of a tiered testing strategy for NM hazard assessment that promotes the more widespread adoption of non-rodent, alternative models and focuses on investigation of inflammation and oxidative stress could make nanotoxicology testing more ethical, relevant, and cost and time efficient.

Keywords:

• Nanomaterial
• nanoparticle
• nanotoxicology
• zebrafish
• in vitro
• 3Rs
• inflammation
• oxidative stress
• neutrophil
• macrophage

Acknowledgements

The authors would like to thank Dr Nikki Gellaty at the UK National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) for providing useful feedback on the content of the manuscript. The authors would also like to thank the reviewers (selected by the editor of the journal) for their anonymous and very constructive feedback on our review.

Declaration of interest

The authors would like to acknowledge funding from the UK National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs), for an ongoing research project which is applying in vitro (neutrophil) models and transgenic zebrafish to investigate the neutrophil response to nanomaterials (Grant number: NC/P001149/1). The review was conducted during the normal course of the authors’ employment, and the authors had sole responsibility for the writing and content of the review. The review, and its conclusions, do not necessarily represent the views of the authors’ employees or their funders. The authors have not engaged in legal or regulatory proceedings during the past five years which are related to the content of this review. This review was not commissioned and the authors have not received additional funding from any sources to write this review.