Abstract

Silver nanoparticles (AgNPs) have been widely used in many commercial products because of their excellent antibacterial ability.^1,2 The AgNPs may be released into the environment during the production, transportation, erosion, washing or disposal of AgNPs-containing products, and hence AgNPs are considered as an important source of silver contamination.¹ AgNPs would gradually accumulate in the ocean, and affect the animals via food-web chain.^1,2,3 The concentration of AgNPs in the ocean will increase and pose a toxicity risk to the marine organisms,^2,3 especially the animals at higher trophic level. Cetaceans as top predator of ocean may have been exposed to the silver and AgNPs, and suffered the negative health impact by the deposition of these silver compounds in their bodies.⁴ Therefore, the interaction between silver deposition and biological systems is drawing a serious concern for the sake of one health consideration. In the present study, we utilized a histochemical technique to autometallographically amplify the silver atoms in the liver and kidney of cetaceans:^5,6 Seven kidney and 6 liver tissues from 7 cetacean species including 2 Kogia spp., 1 Grampus griseus, 3 Lagenodelphis hosei, and 1 Stenella attenuate. The silver concentration was measured by inductively coupled plasma mass spectrometry (ICP-MS). The formalin-fixed, paraffin-embedded tissues were stained with silver enhancement (SE) staining, and semi-quantitative analysis on these tissue sections was performed by using Image J. Significant positive correlation between the results of ICP-MS and SE staining was found in liver (Pearson correlation coefficient =0.834, p=0.039) and kidney (Spearman correlation coefficient = 0.964, p=0.000). Different patterns of positive signals under SE staining were detected, including 1) variably sized brown to black dots in epithelial cells of proximal renal tubules, hepatocytes, and Kupffer cells; 2) golden-yellow to brown positive signals were noted on the basement membrane of renal tubules and glomeruli. It's speculated the different patterns of positive signals may be associated with different silver compounds accumulated in tissues.⁷ In conclusion, the SE staining is a relatively convenient methodology to localize silver and AgNPs in tissues and cells, and can be further used for global, spatio-temporal and cross-species studies.

Acknowledgements

The authors want to thank all the people of Taiwan Cetacean Stranding Network including the costal guards, laboratory of cetacean research in National Taiwan University, and Taiwan Cetacean Society for sample collection and storage.

* Presenting author

References

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