Less is more: biological effects of NiSe2/rGO nanocomposites with low dose provide new insight for risk assessment

Highlights: • Compared with acute and repetitive exposure, different toxicity was triggered by lose dose NMs under the long-term exposure. • No significant differences could be found between the NiSe₂/rGO with different surface defects. • The physicochemical properties of NMs might not be regarded as the predominant predictor for real risk assessment. Nickel selenide nanomaterials (NiSe₂ NMs) with different vacancies demonstrated high catalytic activity as electrocatalyst in oxygen evolution reaction. As the growing needs of the industrial applications in electrocatalyst, the increased occupational exposure and environmental releasing of NMs would be unavoidable. While, much efforts have been made to evaluate the ecological safety of such engineered NMs at unrealistically high concentrations, failed to provide the comprehensively guideline for exposure thresholds. To supplement the current knowledge gap, we testified the cytotoxicity of NiSe₂/rGO nanocomposites with different surface defects under more realistic exposure mode. Compared with the short-term exposure and repetitive exposure, rat lung macrophages exhibited the augmented oxidative stress, dysfunction of mitochondria, damage of DNA and disorder of calcium homeostasis under the long-term NiSe₂/rGO exposure. Noteworthily, no significant differences could be found between the NiSe₂/rGO with different surface defects, indicated that the defect type of NMs were not the accurate predictor for real risk assessment. Collectively, the study provided the real potential toxic effects and exposure thresholds of NMs that might be highly possible industrial produced, and appealed the new insight for risk assessments of engineered NMs under the long-term exposure, which exhibited difference from the traditional evaluation of short-term and repetitive exposure.