Noncytotoxic Mn-doped ZnSe/ZnS quantum dots for biomedical applications

Quantum dots (QDs) are of high interest in the biomedical field. The most widely used and commercially available CdSe/ZnS QDs have a highly toxic Cd component. High-efficiency luminescent Cd-free Mn-doped ZnSe/ZnS QDs are a reasonable alternative to CdSe/ZnS QDs; however the actual cytotoxicity of ZnSe:Mn/ZnS QDs is relatively unknown. In this study, we apply the ApoTox-GloTM Triplex assay to test for cell cytotoxicity, viability, and induced apoptosis, by treating macrophage cells with different concentrations of peptide-coated ZnSe:Mn/ZnS QDs at four different incubation times: 6, 12, 24, and 48 hours. At the concentrations used, which varied between 0.03 μM to 0.25 μM, the macrophage cells showed very little cytotoxic effect. However, cell viability began to decrease with increasing QD concentration beginning with the 12 hour incubation time, with fairly consistent results for 24 and 48 hour incubation times as well. Also, the macrophage cells expressed a measurable degree of induced apoptosis, which scaled with concentration. While cytotoxicity did not seem to be an issue with macrophage cells treated with the peptide-coated Mn-doped ZnSe/ZnS QDs, the drop in cell viability and the increase in induced apoptosis suggest an antiproliferation effect within the macrophage cell culture.