The application of nanoparticles (NPs) in industry is on the rise, along with the potential for human exposure. While the toxicity of microscale equivalents has been studied, nanoscale materials exhibit different properties and bodily uptake, which limits the prediction ability of microscale models. Here, we examine the cytotoxicity of seven transition metal oxide NPs in the fourth period of the periodic table of the chemical elements. We hypothesized that NP-mediated cytotoxicity is a function of cell killing and suppression of cell proliferation. To test our hypothesis, transition metal oxide NPs were tested in a human lung cancer cell model (A549). Cells were exposed to a series of concentrations of TiO2, Cr2O3, Mn2O3, Fe2O3, NiO, CuO, or ZnO for either 24 or 48 h. All NPs aside from Cr2O3 and Fe2O3 showed a time-and dose-dependent decrease in viability. All NPs significantly inhibited cellular proliferation. The trend of cytotoxicity was in parallel with that of proliferative inhibition. Toxicity was ranked according to severity of cellular responses, revealing a strong correlation between viability, proliferation, and apoptosis. Cell cycle alteration was observed in the most toxic NPs, which may have contributed to promoting apoptosis and suppressing cell division rate. Collectively, our data support the hypothesis that cell killing and cell proliferative inhibition are essential independent variables in NP-mediated cytotoxicity.


Biological Sciences

Research Center/Lab(s)

Center for Research in Energy and Environment (CREE)


This research was funded by the Missouri S&T cDNA Resource Center.

Keywords and Phrases

Apoptosis; Cell cycle; Cell proliferation; Nanoparticle; Transition metal oxide

International Standard Serial Number (ISSN)

1661-6596; 1422-0067

Document Type

Article - Journal

Document Version

Final Version

File Type





© 2020 The Authors, All rights reserved.

Creative Commons Licensing

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Publication Date

01 Mar 2020

PubMed ID


Included in

Biology Commons