Abstract:

OBJECTIVE: To investigate the mechanism of cytotoxicity of CdSe/ZnS quantum dots (CdSe/ZnS QDs) on HepG2 cells. METHODS: Morphological images of CdSe/ZnS QDs were obtained with a transmission electron microscope (TEM) and the fluorescence spectra of the QDs were determined by a spectrophotometer. After treatment with 0,0.5 and 5 nmol/L CdSe/ZnS QDs for 4 hours, the HepG2 cells were imaged under a laser scanning confocal microscope (LSCM) and the uptake efficiency of the QDs was evaluated quantitatively using a flow cytometry machine. After treatment for 24 and 48 hours, the effect on cell proliferation was measured using the MTT assay. The Western blot assay was used to evaluate the effect on apoptosis-related proteins, Casepase-9 and Casepase-3. RESULTS: CdSe/ZnS QDs had a particle size of around 10 nm and the nanocrystals were highly mono-dispersed. The QDs exhibited a broad absorption spectrum from 250 nm to 500 nm and a narrow emission spectrum from 600 nm to 700 nm. The QDs entered cells and remained mostly in the cytoplasm within 4 hours. The uptake efficiency of the QDs was up to 99%. Compared with controls, cells treated with 0.5 and 5 nmol/L QDs for 24 hours exhibited no obvious suppression on cell proliferation but showed highly suppressed cell proliferation 48 hours later (P < 0.05). Compared with controls, the expression levels of Caspase-9 and Caspase-3 were increased in QDs-treated cells. CONCLUSION: The results suggest that CdSe/ZnS QDs which were taken in by HepG2 cells inhibited cell proliferation. The inhibition could be related to the induction of Caspase-9 and Caspase-3 expression.

Key words: CdSe/ZnS, quantum dots, cell proliferation, apoptosis, cytotoxicity