CdSe/ZnS quantum dots induce photodynamic effects and cytotoxicity in pancreatic cancer cells

Figure 1 Characterization of CdSe/ZnS quantum dots. A: TEM image of CdSe/ZnS QDs; B: Absorbance and emission of CdSe/ZnS QDs. QDs: Quantum dots.

Figure 2 Cell viability of SW1990 cells was inhibited by CdSe/ZnS quantum dots with or without illumination. A: SW1990 cells were treated with various concentrations of CdSe/ZnS QDs (0, 0.5, 1.0, 1.5, 2.0, 2.5 μmol/L); incubation time was 3 h; light dose was 20 J/cm²; B: SW1990 cells incubated with CdSe/ZnS QDs (1.5 μmol/L) for 0, 1, 3, 6 and 12 h and illuminated (light dose was 20 J/cm²); C: SW1990 cells alone or incubated with CdSe/ZnS QDs (1.5 μmol/L) for 3 h and illuminated with different light doses (0, 10, 20 and 30 J/cm²). ^bP < 0.01 vs related group without light. QDs: Quantum dots.

Figure 3 Ultrastructural changes in SW1990 cells induced by CdSe/ZnS quantum dots with or without illumination (TEM, magnification × 2000). A: normal SW1990 cells; B: treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h) and illumination (20 J/cm²); C: treated with CdSe/ZnS QDs (2 μmol/L, 3 h) and illumination (20 J/cm²). QDs: Quantum dots.

Figure 4 Apoptosis and necrosis were observed in SW1990 cells treated by CdSe/ZnS quantum dots with illumination (Hochest 33342/PI nucleus staining, magnification × 100). A: normal SW1990 cells; B: SW1990 cells with illumination (20 J/cm²); C: SW1990 cells treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h); D: SW1990 cells treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h) and illumination (20 J/cm²). The white arrow shows dead cells. QDs: Quantum dots.

Figure 5 Apoptosis and necrosis were observed in SW1990 cells treated by CdSe/ZnS quantum dots with illumination. A: normal SW1990 cells; B: SW1990 cells with illumination (20 J/cm²); C: SW1990 cells treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h); D: SW1990 cells treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h) and illumination (20 J/cm²). FCM of SW1990 cells showed that SW1990 cells had a higher apoptosis rate (53.2%) in Group D than in Groups A, B and C. QDs: Quantum dots.

Figure 6 Reactive oxygen species generation was detected after treatment of CdSe/ZnS quantum dots with illumination. A: Fluorescent images of ROS in SW1990 cells (Bar: 200 μm); B: Relative ROS level measured by FCM; C: Cell viability of SW1990 cells by CCK-8 assay. Control: normal SW1990 cells; Light: SW1990 cells with illumination (20 J/cm²); QDs: SW1990 cells treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h); PDT: SW1990 cells treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h) and illumination (20 J/cm²). NAC: N-acetylcysteine, a ROS scavenger, 5 mmol/L NAC was added to the cell culture for 1 h before treatment. QDs: Quantum dots; ROS: Reactive oxygen species.

Figure 7 Changes in mRNA expression levels of Bax, Bcl-2 and caspase-3 following CdSe/ZnS quantum dots with illumination. A: Normal SW1990 cells; B: SW1990 cells with illumination (20 J/cm²); C: SW1990 cells treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h); D: SW1990 cells treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h) and illumination (20 J/cm²). ^bP < 0.01 vs group A. QDs: Quantum dots.

Figure 8 Changes in protein expression levels of Bax, Bcl-2 and caspase-3 following CdSe/ZnS quantum dots with illumination. A: Normal SW1990 cells; B: SW1990 cells with illumination (20 J/cm²); C: SW1990 cells treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h); D: SW1990 cells treated with CdSe/ZnS QDs (1.5 μmol/L, 3 h) and illumination (20J/cm²). QDs: Quantum dots.

Figure 9 Quantum dots-photodynamic therapy-induced cell death via apoptosis. A: Cell viability of SW1990 cells by CCK-8 assay; B: Hochest 33342/PI nucleus staining of apoptotic and necrotic SW1990 cells (magnification × 100), white arrow indicates dead cells; C: Percentage of apoptotic and necrotic SW1990 cells by FCM. SW1990 cells were pretreated with or without Z-VAD-FMK (50 μmol/L) for 1 h and then treated with QD-PDT (1.5 μmol/L, 3 h, 20 J/cm²). QDs: Quantum dots; PDT: Photodynamic therapy; FCM: Flow cytometry; CCK-8: Cell Counting Kit-8; PI: Propidium iodide.