Toxicity assessment of gold ions and gold nanoparticles to golden perch larvae (Macquaria ambigua)

Abstract

Golden perch (Macquaria ambigua) is a freshwater game-fish native to central and southeast Australia. Larvae of this fish species were used in two different types of experiments to evaluate the effects of short-term exposures (up to 6 days) to aqueous gold, 5 nm gold nanoparticles (AuNPs), or 50 nm AuNPs. Relative to the control, increased gold concentrations corresponded with yolk-sac edema (swelling). Larvae exposed to 50 μM of 5 nm AuNPs had yolk-sacs that were ~1.5 times larger resulting in the appearance of bent notochords. After two days of exposure, 100% mortality was observed. Total mortalities were <25% in the other larvae–gold systems, suggesting that these larvae can quickly adapt to the presence of gold. In terms of an oxidative stress response, the larvae from all systems did not express high enzymatic activity. The state of the gold determined how much could be taken up (or immobilised) by a larva. Aqueous gold and 5 nm AuNPs easily pass through cells; therefore, larvae exposed to these forms of gold contained the highest concentrations. Scanning electron microscopy confirmed that cells comprising the epithelium and fins contained AuNPs. Aqueous gold was reduced to nanometre-scale particles within cells. Comparatively, 5 nm AuNPs appeared to be aggregated within cells forming clusters hundreds of nanometres in size. On the contrary, 50 nm AuNPs were not observed within cells but were detected within larvae by (single particle) inductively coupled plasma mass spectroscopy, suggesting that these AuNPs were probably taken up through the mouth or gills. The results of the present study demonstrate that exposure to AuNPs had adverse effects on developing golden perch larvae. Additionally, these effects were dependent on the size of the AuNPs.

Natural Nanoparticles of the Critical Element Tellurium

“…In the case of silver (Ag), Ag NPs are a noted anti-bacterial agent (Desireddy et al, 2013;Xu et al, 2020) and their behaviour in the environment is markedly different from macroscopic Ag, which is comparatively unreactive (McGillicuddy et al, 2017;de Souza et al, 2019). Studying metals such as Au (Reith et al, 2013;Kato et al, 2019;Sanyal et al, 2019;Shuster et al, 2021) and Pt (Reith et al, 2014(Reith et al, , 2019Asztemborska et al, 2015;Ksią żyk et al, 2015) has also led to a new understanding of environmental behaviour and toxicity of elements previously thought to be inert in natural contexts. Missen et al (2022) observed Te NPs on the surface of native tellurium grains (i.e., coarse-grained Te 0 formed from hydrothermal fluids) undergoing weathering at the Bambolla mine, Moctezuma, Mexico (Fig.…”