Multi-system evaluation of quantum dots' biotoxicity: DNA integrity, cell damage, and viability in organisms

Abstract

This research involved a comprehensive multisystemic evaluation of the biotoxicity of three tracers (carbon quantum dots synthesized from citric acid and ethylenediamine “N-CQD”, commercial cadmium-tellurium quantum dots “CdTe-QD”, and a conventional tracer based on fluorinated benzoic acid derivatives “SB-tracer”). Biotoxicity was assessed at three organizational levels: DNA, cellular, and multicellular eukaryotic system, using the comet assay and chromosomal aberration tests, cytotoxicity assays, and plant growth profiling, respectively. The results revealed significant DNA damage induced by CdTe-QD and SB-tracer, with olive tail moment (a measure of DNA degradation) values up to 15 times higher than those observed for N-CQD in the comet assay. Cytotoxicity revealed an half maximal inhibitory concentration (IC₅₀) > 1000 mg L⁻¹ for N-CQD, 7.35 mg L⁻¹ for CdTe-QD, and 600.06 mg L⁻¹ for SB-tracer, classifying the samples as non-cytotoxic, cytotoxic, and moderately cytotoxic, respectively. However, the chromosomal aberration results for SB-tracer revealed its lethality by inhibiting the lymphocyte proliferation required for the test. Melon and sunflower seed sprouts were employed as multicellular eukaryotic models for toxicity evaluation at higher organizational levels, and it was observed that SB-tracer has a deleterious effect on germination, while N-CQD increased sprout biomass by up to 19 times compared to water irrigation, a result attributed to their positive effect on photosynthetic mechanisms. Finally, the non-toxic and protective effects of N-CQD can be attributed to their high ORAC (oxygen radical absorbance capacity) value considered in this research, which is associated with the prevention of damage to key biomolecules such as DNA and the promotion of cell growth. These results highlight the feasibility and potential use of CQDs as a safe alternative for both the environment and health, with the potential to substitute substances conventionally employed by different industries as multipurpose tracers. To the best of our knowledge, this is the first study to comprehensively evaluate the biotoxicity of QDs at multiple biological organization levels.