Cytotoxicity and genotoxicity of cadmium oxide nanoparticles evaluated using in vitro assays
Orza, Annamaria Ioana
Biris, Alexandru S.
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Cadmium oxide nanoparticles (CdO NPs) are among some of the most studied and industrially used metal oxide NPs. They have been widely used for industrial application, such as paint pigments and electronic devices, and medical therapeutics. With increasing use of CdO NPs and concerns for their potential adverse eﬀects on the environment and public health, evaluation of the cytotoxicity and genotoxicity of CdO NPs becomes very important. To date, there is a limited understanding of the potential hazard brought by CdO NPs and a lack of information and research, particularly on the genotoxicity assessment of these NPs. In this study, 10 nm CdO core-PEG stabilized NPs were synthesized, characterized and used for evaluation of CdO NPs’ cytotoxicity and genotoxicity. Release of cadmium ions (Cd+2) from the CdO NPs in cell culture medium, cellular uptake of the NPs, and the endotoxin content of the particles were measured prior to the toxicity assays. Cytotoxicity was evaluated usingthe MTSassay,ATPcontent detection assay, andLDHassay. Genotoxicity wasassessed using the Ames test, Comet assay, micronucleus assay, and mouse lymphoma assay. The cytotoxicity of cadmium chloride (CdCl2) was also evaluated along with that of the CdO NPs. The results showed that endotoxin levels within the CdO NPs were below the limit of detection. CdO NPs induced concentration-dependent cytotoxicity in TK6 and HepG2cells withthe MTS, ATP andLDH assays. Although thegenotoxicity ofCdONPswas negative inthe Ames test, positive results were obtained with the micronucleus, Comet, and mouse lymphoma assays. The negative response of CdO NPs with the Ames test may be the result of unsuitability of the assay for measuring NPs, while the positive responses from other genotoxicity assays suggest that CdO NPs can induce chromosomal damage, single or double strand breaks in DNA, and mutations. The toxicity of the CdO NPs results from the NPs themselves and not from the released Cd+2, because the ions released from the NPs were minimal. These results demonstrate thatCdO NPsarecytotoxic and genotoxic and provide newinsights into riskassessment ofCdO NPs for human exposure and environmental protection.