While carbon-based materials have spearheaded numerous breakthroughs in biomedicine, they also have procreated many logical concerns on their overall toxicity. carbon dots (cDs) as a respectively new member have been extensively explored in nucleus directed delivery and bioimaging due to their intrinsic fluorescence properties coupled with their small size and surface properties. Although various in vitro/in vivo studies have shown that CDs are mostly biocompatible, sufficient information is lacking regarding genotoxicity of them and underlying mechanisms. This study aims to analyze the real-time cytotoxicity of super tiny CDs (2.05 ± 0.22 nm) on human breast cancer cells (MCF7) and human primary dermal fibroblast cell cultures (HDFa) by xCELLigence analysis system for further evaluating their genotoxicity and clastogenicity to evaluate the anti-tumor potential of cDs on breast adenocarcinoma. As combined with flow cytometry studies, comet assay and cytokinesisblock micronucleus assay suggest that the CDs can penetrate to the cell nuclei, interact with the genetic material, and explode DNA damage and G0/G1 phase arrest in cancer cells even at very low concentrations (0.025 ppm) which provide a strong foundation for the design of potentially promising cD-based functional nanomaterials for DnA-damage induced treatment in cancer therapy. Functional nanomaterials that can better target cancer cells that will improve prevention and therapy could be accomplished by the combined efforts of nanotoxicologists, cancer biologists and nanobiomaterial scientists focused on toxicology and related cancer therapy. Engineering carbon-based nanomaterials and their applications are among the most dynamic fields in modern advanced materials science and engineering 1-3. To date, various carbon nanomaterials such as carbon nanotubes 4,5 , fullerenes 6 , graphene 7,8 , graphene oxides 9 , carbon diamonds 10,11 , and carbon dots 12,13 have been synthesized and reported by various researchers. Among these, CDs have become particularly interesting because of their unique physical and chemical properties such as thermal and electrical conductivity, high mechanical strength together with their unique optic and fluorescence features 14-16. They have been used in bio-imaging, drug delivery, nucleus targeting, and labeling, photodynamic therapy, optoelectronics, solar cells, photocatalyst design, photodetectors, and many other biological and engineering fields 17-26. Several methods are available for the synthesis of CDs, namely, laser ablation 15 , electro-oxidation 27 or oxidative acid treatment 12 ; while nowadays, less laborsome and cheaper methods such as hydrothermal 28 and thermal synthesis 24,29,30 , microwave-assisted hydrothermal synthesis 31 , ultrasound synthesis 32 , etc. are popularly exercised. CDs can be synthesized either from inorganic materials 19,33 such as graphene 34 , carbon black 35 , and candle soot 12
