FTIR microscopy reveals distinct biomolecular profile of crustacean digestive glands upon subtoxic exposure to ZnO nanoparticles

Abstract

Biomolecular profiling with Fourier-Transform InfraRed Microscopy was performed to distinguish the Zn²⁺-mediated effects on the crustacean (Porcellio scaber) digestive glands from the ones elicited by the ZnO nanoparticles (NPs). The exposure to ZnO NPs or ZnCl₂ (1500 and 4000 µg Zn/g of dry food) activated different types of metabolic pathways: some were found in the case of both substances, some only in the case of ZnCl₂, and some only upon exposure to ZnO NPs. Both the ZnO NPs and the ZnCl₂ increased the protein (∼1312 cm⁻¹; 1720–1485 cm⁻¹/3000–2830 cm⁻¹) and RNA concentration (∼1115 cm⁻¹). At the highest exposure concentration of ZnCl₂, where the effects occurred also at the organismal level, some additional changes were found that were not detected upon the ZnO NP exposure. These included changed carbohydrate (most likely glycogen) concentrations (∼1043 cm⁻¹) and the desaturation of cell membrane lipids (∼3014 cm⁻¹). The activation of novel metabolic pathways, as evidenced by changed proteins’ structure (at 1274 cm⁻¹), was found only in the case of ZnO NPs. This proves that Zn²⁺ are not the only inducers of the response to ZnO NPs. Low bioavailable fraction of Zn²⁺ in the digestive glands exposed to ZnO NPs further supports the role of particles in the ZnO NP-generated effects. This study provides the evidence that ZnO NPs induce their own metabolic responses in the subtoxic range.

• Changed protein structure
• Porcellio scaber
• square-wave voltammetry
• ZnCl₂
• ZnO dissolution

Acknowledgements

The authors would like to thank Professor Marjan Veber from the Faculty of Chemistry and Chemical Technology for providing us with an access to his lab; Vesna Arrigler, Zdenka Držaj, Jolanda Furlan and Mojca Žitko from the same faculty for their technical assistance; and Matej Hočevar from the Institute of Metals and Technologies for the access to the electron microscopy.

Declaration of interest

The authors report no conflict of interest. The authors alone were responsible for the content and the writing of the paper. The paper is part of the PhD work of Tea Romih, who received funding from Ministry of Education, Science and Sport of the Republic of Slovenia by the grant “Innovative scheme of co-funding doctoral studies for promoting co-operation with the economy and solving contemporary social challenges” under Grant Number 1291. The research was also funded by the Slovenian Research Agency (ARRS; J1-4109) and the EU FP7 nanoMILE project (Grant agreement: 310451; Call ID: FP7-PEOPLE-2013-ITN).

Supplementary material available online

Supplementary Figures S1 - S5, Method description S1 to S3 and Table S1 and S2