Copper-oxide nanoparticles effects on goldfish (Carassius auratus): Lethal toxicity, haematological, and biochemical effects.

The advancement of nanotechnology and the widespread use of nanoparticles (NPs) in various industries have highlighted
the importance of studying the potential harmful effects of nanomaterials on organisms. This study aimed to evaluate the
lethal toxicity thresholds of Copper Oxide Nanoparticles (CuO-NPs). The investigation focused on examining the sub lethal toxicity effects of CuO-NPs on blood parameters, as well as their influence on the gill tissue and liver of goldfish
(Carassius auratus). Goldfish were exposed to varying concentrations of CuO-NPs (10, 20, 30, 40, 60, 80, and 100 mg/L)
for 96 h. The Probit software was employed to determine the LC50 (lethal concentration causing 50% fish mortality) by
monitoring and documenting fish deaths at 24, 48, 72, and 96-hour intervals. Subsequently, sub-lethal concentrations of
5% LC50 (T1), 10% LC50 (T2), and 15% LC50 (T3) of CuO-NPs were administered based on the LC50 level to investigate
their effects on haematological parameters, encompassing the number of red blood cells and white blood cells, hematocrit
and haemoglobin levels, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin
concentration. Additionally, histopathological examinations were conducted on the gill and liver tissues of the studied fish.
Results indicated concentration-response of fish mortalities. In general, changes in the blood biochemical parameters of
fish exposed to sub-lethal concentrations of CuO-NPs included a significant decrease in leukocyte count and glucose level
and an increase in protein and triglyceride levels. Furthermore, an escalation in tissue damage such as gill apical and basal
hyperplasia, lamellae attachment, squamous cell swelling, blood cell infiltration, and cellular oedema in gills tissue. and
bleeding, increased sinusoidal space, necrosis, lateralization of the nucleus, cell swelling, and water retention in the liver.
The findings showed dose-dependent increasing toxicity in goldfish specimens exposed to CuO-NPs.