Evaluate the potential environmental toxicity of quantum dots on ciliated protozoa by microcalorimetry

In the present study, we evaluated the toxic effects of mercaptoacetic acid (MAA)-capped CdSe QDs and CdSe/ZnS QDs to particle-ingesting model ciliated protozoa Tetrahymena thermophila BF5 (T. thermophila BF5) by using a TAM air isothermal microcalorimeter. These results suggested that both MAA-CdSe QDs and MAA-CdSe/ZnS QDs were indeed acutely toxic for T. thermophila BF5 growth in a dose-dependent manner, and the toxicities of both MAA-CdSe QDs and MAA-CdSe/ZnS QDs increased dramatically after UV irradiation due to the liberation of more toxic Cd2+, which indicated that the toxicity of MAA-CdSe/ZnS QDs was less than that of MAA-CdSe QDs. Furthermore, the toxicity of different ligands-capped CdSe/ZnS QDs on T. thermophila BF5 was also investigated. The uptake of MAA-CdSe/ZnS QDs and adenosine 5′-monophosphate (AMP)-CdSe/ZnS QDs by cells and the morphological change during the process of T. thermophila BF5 growth incubated with these QDs were further studied by fluorescence inverted microscopy.