X-ray spectrometry imaging and chemical speciation assisting to understand the toxic effects of copper oxide nanoparticles on zebrafish (Danio rerio)

Abstract

Currently, copper nanoparticles are used in various sectors of industry, agriculture, and medicine. To understand the effects induced by these nanoparticles, it is necessary to assess the environmental risk and safely expand their use. In this study, we evaluated the toxicity of copper oxide (nCuO) nanoparticles in Danio rerio adults, their distribution/concentration, and chemical form after exposure. This last assessment had never been performed on copper-exposed zebrafish. Such evaluation was done through the characterization of nCuO, acute exposure tests and analysis of distribution and concentration by microstructure X-ray fluorescence spectroscopy (µ-XRF) and atomic absorption spectroscopy (GF-AAS). Synchrotron X-ray absorption spectroscopy (XAS) was performed to find out the chemical form of copper in hotspots. The results show that the toxicity values of fish exposed to nCuO were 2.4 mg L⁻¹ (25 nm), 12.36 mg L⁻¹ (40 nm), 149.03 mg L⁻¹ (80 nm) and 0.62 mg L⁻¹ (CuSO₄, used as a positive control). The total copper found in the fish was in the order of mg kg^-1 and it was not directly proportional to the exposure concentration; most of the copper was concentrated in the gastric system. However, despite the existence of copper hotspots, chemical transformation of CuO into other compounds was not detected.

Keywords:

• Zebrafish
• CuO
• nanoparticles
• accumulation
• XRF
• XANES

Acknowledgements

The authors are grateful to the Brazilian Synchrotron Light Laboratory for beam time under proposal 20180247, Dr. C. Perez is kindly acknowledged for his assistance during the µ-XANES measurements.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by FAPESP Young Researcher Awards 2015/05942-0 and Multiuse equipment Grant 2015-19121-8. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001 and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) – Process 141014/2019-9 and Process 429309/2018-0. H. W. P. Carvalho is the recipient of a research productivity fellowship from the Brazilian National Council for Scientific and Technological Development (CNPq) [grant # 306185/2020-2].