Effects of CuSO₄ and CuO nanoparticles on fish gut motility in Altantic salmon, Salmo salar

Innovation with metallic nanoparticles (NPs) is increasing, but their effects on the gastrointestinal physiology of fishes is poorly understood. This study explored the effects of CuSO₄ and CuO NPs (primary size; 10-20 nm) on gut motility of Salmo salar (Atlantic Salmon), using an isolated gut preparation to record the frequency and amplitude of contractions. The study design used each gut as its own control, with measurements before, during and after exposure to each substance. Nanoparticle tracking analysis (NTA), as expected, showed some particle aggregation of CuO NPs in physiological saline with a hydrodynamic diameter of (mean ± S.E., n = 10) 242 nm ± 42. Exposure to 0.1 mg/L of Cu as CuSO₄ displayed no significant effect on both the frequency and amplitude when compared to controls without Cu, and the CuO NP treatment. The CuO NP treatment displayed a similar effect on contractions when compared to controls, where the frequency and amplitude of contractions remained unchanged. However, a significant decrease in number of contractions between pre- and post-exposure phases in the CuSO₄ treatment was observed. Impaired contractility remained evident in clean saline after exposure to CuSO₄, indicating a continued post-exposure effect. In contrast, guts exposed to CuO NP showed similar numbers of contractions in the exposure and post-exposure phases, indicating no further deterioration. Total Cu concentrations in the tissue as dry weight (dw) were significantly higher in guts exposed to CuO NPs (1060 µg/g dw) than CuSO₄ (24 µg/g dw), but CuSO₄ was more hazardous with respect to gut motility than the nano form.