| Quantum dots(QDs) are semiconductor fluorescent nanocrystals that tightly confine electrons and electron holes in all three spatial dimensions. Due to their optical properties, QDs are widely used in optics, electricity, information science and biology. The synthesized QDs are often released into the environment without further treatment. However, very little are known about their toxicity. In this study, we first demonstrated that i.v. injected QDs are accumulated in the immune organs. As the first line of defense against foreign substances, immune system plays an irreplaceable role in survival and development. Therefore, we assessed the potential toxicity of the QDs on the immune system both in vivo in BALB/c mice and in vitro in macrophage and lymphocytes immune cells.Part 1. The immunotoxicity of Cd Se/Zn S QDs in vitro in macrophage and lymphocytes immune cells:1) The toxic effects of different concentration of Cd Se/Zn S QDs on macrophages RAW264.7 cells were evaluated. The uptake of QDs by macrophages was observed by confocal imaging and flow cytometry. The cell vialibity was detected by CCK-8 assay. The intracellular reactive oxygen species(ROS) were detected by flow cytometry and the apoptosis of macrophages were analyzed by Western Blot. In addition, phagocytic capacity of QDs-treated macrophages was determined by neutral red phagocytosis assay.Our results showed that Cd Se/Zn S QDs could be uptaked by macrophages RAW264.7 cells with high efficiency(>90%), and they are located in cytoplasm. Cd Se/Zn S QDs treatment significantly suppressed macrophage cell viability, induced the formation of ROS, and increased the expression of apoptosis related protein Caspase-3 and Caspase-9. Besides, the phagocytic ability of macrophages treated with QDs was also changed.2) Lymphocytes isolated from mouse spleen were also used to evaluate the toxicityof Cd Se/Zn S QDs. The uptake of QDs by lymphocytes was determined by flow cytometry, and the vialibity of QDs-treated cell was detected by CCK-8 assay. After QDs exposure, the ability of lymphocyte to release cytokines(TNF-? and IL-6) in response to foreign substances(Cp G-ODN and LPS) were measured by ELISA, and the activity of lymphocyte transformation was determined by CCK-8 assay.Our results showed that lymphocytes could not take-up Cd Se/Zn S QDs. However, treatment with QDs increased lymphocytes cell viability. When lymphocytes were exposed to high concentration(2.5 n M) of QDs, their ability of releasing cytokines(TNF-? and IL-6) in response to Cp G-ODN significantly increased. In addition, QDs treatment significantly decreased the transformation ability of lymphocytes in response to LPS, but not Con A. These results suggested that Cd Se/Zn S QDs could inhibit the transformation ability of B lymphocytes, but not T lymphocytes.Part 2. The immunotoxicity of Cd Se/Zn S QDs in vivo in BALB/c mice:To assess the in vivo immune effects, the Cd Se/Zn S QDs were injected into the BALB/c mice intravenously and the body weight changes were monitored. Accumulation of QDs elements in major organs and blood were detected by ICP-MS. The immune organs were observed by fluorescence imaging. The blood routine test was measured by blood cell analyzer. The immune organic histopathology was analysed by HE staining. The lymphocyte subtype proportions were determined by flow cytometer. The immune functions of spleen were evaluated by ELISA, and phagocytic function of the peritoneal macrophages was determined by chicken red blood cell phagocytosis assay.Our results showed that Cd Se/Zn S QDs were accumulated in the immune organs(spleen, thymus) for over 42 days. Importantly, the lymphocytes from spleen of QDs-treated mice showed significantly reduced cell viability, altered subtype proportions, increased TNF-? and IL-6 release, and reduced transformation ability in response to LPS. However, no significant change to body weight, hematology, organic histopathology and phagocytic function of peritoneal macrophages in QDs-treated mice were noticed as compare to that of the control mice.In this paper, we systematically evaluated the immunotoxicity of Cd Se/Zn S QDs by in vitro cell models and in vivo mouse model. Our results strongly suggested that pre-exposure of Cd Se/Zn S QDs influence immune cell function and impair immune responses towards foreign stimuli, which in turn could cause decreased defense ability against infection and increased susceptibility of hosts to diseases. Knowledge gained from this research provides more comprehensive information for the QDs immunotoxicity, and facilitates the QDs biological safety evaluation, as well as its application in biomedical field. |
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