Toxicity of nickel oxide nanoparticles in Capoeta fusca, using bioaccumulation, depuration, and histopathological changes

BACKGROUND AND OBJECTIVES: The nanoparticles has been discussed in terms of their adverse global impacts on health and health inequity. Metal oxide nanoparticles and their salts can have varied toxic effects on different tissues in the aquatic environments. The aim of present study was to assess the toxicity of nickel oxide nanoparticles in relation to different nickel salts. METHODS: Acute toxicity of nickel oxide nanoparticles, nickel sulfate, nickel nitrate and nickel chloride, in black fish was investigated. A total of 125 fish were randomly assigned to a control group (n=25) and four exposure groups (n=25 per group). After 28 days of exposure, the bioaccumulation of nickel oxide nanoparticles in gill, intestine, liver, and kidney of the fish was determined by killing half of them in each group and dissecting their tissues. The remaining fish were placed in clean water for another 28 days and the depuration rate was estimated. FINDINGS: The LC50-96 values reported for nickel oxide nanoparticles, nickel sulfate, nickel nitrate and nickel chloride were 195, 120, 138 and 91 milligrams per liter, respectively. Therefore, nickel chloride had a higher toxicity compared to nickel oxide nanoparticles, nickel sulfate and nickel nitrate. The highest rate of nickel oxide nanoparticles bioaccumulation was observed in the gill (0.40±0.08 microgram per gram), intestine (41.82±16.95 microgram per gram), liver (2.16±1.82 microgram per gram), and kidney (2.16±1.26 microgram per gram) of the fish. The highest depuration rate of nickel oxide nanoparticles, nickel sulfate, nickel nitrate, and nickel chloride was recorded in the intestinal tissue of the fish. The lowest depuration rate of nickel oxide nanoparticles, nickel sulfate and nickel nitrate was observed in the kidney tissue of the fish. Also, the lowest depuration rate of nickel chloride was witnessed in the gill tissue of the fish. Histopathological anomalies were detected in the fish exposed to nickel oxide nanoparticles. These anomalies were fusion of lamellae, lamellar synechiae, curvature and oedema in the gill; increased number of goblet cells and cell swelling; and degradation of villi structure and expansion of villi structure in the intestine. CONCLUSION: The study conclusively demonstrated that nickel oxide nanoparticles were eco-toxic and harmful to aquatic organisms. Strong global nickel oxide nanoparticles regulations must be enforced to prevent further environmental contamination with nanoparticles.