Degradation related cytotoxicity of quantum dots

Before using semiconductor quantum dots (QDs) in biomedical applications in vivo, it´s important to know about their interaction with biological surroundings, stability in living organisms, intracellular distribution and cytotoxicity. We have investigated CdTe-MPA and (CdSe)ZnS-MUA QDs in the osteosarcoma U2-OS cell culture. The changes in photoluminescence spectra of QDs, the localization of QDs in living cells and the influence on the cell viability were studied. We have found that spectra of CdTe - MPA QDs became blue-shifted in the incubation medium and U2-OS cancer cells, which were incubated with these QDs, were inactivated after 24 h. This notable shift from 631 nm to 614 nm implies that QDs degraded releasing Cd²⁺ ions, known to be cytotoxic. On the other hand, the spectra of (CdSe)ZnS-MUA QDs didn´t change and accumulation of these QDs in cells had no impact on their viability after 24 h.