Silica nanoparticles acute toxicity alters ethology, neuro-stress indices, and physiological status of African catfish (Clarias gariepinus)

Abstract

Silica nanoparticles (SiNPs) are a new class of nanomaterials with unique properties due to their nanoscale size. Currently, SiNPs constitute a potential value in aquaculture; nonetheless, misuse induces toxicity to fisheries and ecosystems. Hence, the present prospective is a pioneer study that illustrates the acute toxicity of SiNPs to African catfish, Clarias gariepinus (B.) and the behavioral response in a renewal static system. Moreover, the influence of SiNPs on neuro-related, stress, immune-related, and oxidative stress indices was investigated. Fish groups of average body weights (73.09 ± 2.20 g) were exposed to 96-h of various concentrations of SiNPs including 0, 50, 100, 150, 200, 250, and 300 mg L−1 without water exchange. The value of 96-h LC50 of SiNPs was computed using Finney's probit analysis. Here we show that the exposure of fish to SiNPs resulted in remarkable ethological alterations such as lethargic, surfacing, inactive, slow swimming manner, and nervousness. By increasing the SiNPs concentration, the behavior scores and mortalities reached the upper limit of top values. The comparison with the control revealed a significant dose-dependent effect by increasing in the activity of 8-hydroxy-2-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) with a concomitant elevation in the stress-controlled parameters (cortisol and nor-epinephrin) of all the fish groups undergone the SiNPs exposure. In contrast, there was a clear reduction in the acetylcholine esterase (AChE) level, immunological biomarkers (lysozymes and nitric oxide), and antioxidant enzymes (glutathione peroxidase (GPX) and superoxide dismutase (SOD)) of the exposed groups and the reduction elevated by increasing the SiNPs exposure concentration in comparison to the control group. Based on the study outcomes, the 96-h LC50 of SiNPs recorded 144.54 mg L−1 in C. gariepinus. We anticipate our assay to be a starting point for further applying the one-tenth of 96-h LC50- as an alternative safe treatment in therapy after considering the acute toxicity to preserve the aquaculture production and sustain human health. Additionally, it was approved that, the toxicity by the exposure to SiNPs observed clear alterations in fish behavior, neurological activity, immune and oxidative responses reflecting physiological disturbance.

Keywords

• Silica nanoparticles
• African catfish
• Lethal concentration
• Brain activity
• Immune-antioxidant responses