Center for Chemical Toxicology Research & Pharmacokinetics, North Carolina State University, Raleigh, NC 27606, USA.
Nanomedicine (Lond). 2011 Jul;6(5):777-91. doi: 10.2217/nnm.11.73.
Quantum dots (QDs) are nanoparticles with strong fluorescent emission and are novel tools used in biomedical applications, but the toxicity and mechanism of cellular uptake are poorly understood. QD655-COOH (negative charge, 18 nm) consist of a cadmium/selenide core and a zinc sulfide shell with a carboxylic acid coating with an emission wavelength of 655 nm.
MATERIALS & METHODS: Peripheral blood mononuclear cells were isolated from porcine blood by gradient centrifugation, and monocytes, which are CD14 positive, were purified. Monocytes were differentiated into dendritic cells (DCs) with GM-CSF and IL-4.
Monocytes showed cellular uptake of QD655-COOH, while lymphocytes did not. Monocyte differentiation into DCs increased the cellular uptake by sixfold when dosed with 2 nM of QD655-COOH. Transmission electron microscopy depicted QD655-COOH in the cytoplasmic vacuoles of DCs. Twelve endocytic inhibitors demonstrated QD655-COOH endocytosis in DCs, which was recognized by clathrin and scavenger receptors and regulated by F-actin and phospholipase C. In addition, DC maturation with lipopolysaccharide (LPS) caused an increase in QD655-COOH uptake compared with DCs without LPS stimulation. Viability assays, including 96AQ, CCK-8, alamar blue and ApoTox, exhibited minimal toxicity in DCs dosed with QD655-COOH at 24 h. However, glutathione levels showed a significant decrease with 10 nM of QD655-COOH. Finally, QD655-COOH exposure was associated with a decrease in CD80/CD86 expression after LPS stimulation, suggesting suppression with DC maturation.
These findings shed light on the mechanism of QD655-COOH uptake in DCs and that cellular uptake pathways are dependent on cell type and cell differentiation.
量子点（QD）是具有强荧光发射的纳米颗粒，是生物医学应用中的新型工具，但细胞摄取的毒性和机制还了解甚少。QD655-COOH（带负电荷，18nm）由镉/硒核和锌硫化物壳组成，带有羧酸涂层，发射波长为 655nm。
通过梯度离心从猪血液中分离外周血单核细胞，并纯化出 CD14 阳性的单核细胞。单核细胞用 GM-CSF 和 IL-4 分化为树突状细胞（DC）。
单核细胞表现出对 QD655-COOH 的细胞摄取，而淋巴细胞则没有。当用 2nM 的 QD655-COOH 处理时，单核细胞分化为 DC 会使细胞摄取增加六倍。透射电子显微镜显示 QD655-COOH 位于 DC 的细胞质空泡中。12 种内吞抑制剂显示 QD655-COOH 在 DC 中的内吞作用，这是由网格蛋白和清道夫受体识别的，并受 F-肌动蛋白和磷脂酶 C 调节。此外，与 LPS 一起成熟的 DC 引起的 QD655-COOH 摄取增加与没有 LPS 刺激的 DC 相比。包括 96AQ、CCK-8、alamar blue 和 ApoTox 在内的活力测定显示，在 DC 中用 QD655-COOH 处理 24 小时后几乎没有毒性。然而，用 10nM 的 QD655-COOH 处理后，谷胱甘肽水平显著下降。最后，QD655-COOH 暴露与 LPS 刺激后 CD80/CD86 表达的降低有关，表明 DC 成熟时受到抑制。
这些发现揭示了 QD655-COOH 在 DC 中的摄取机制，并且细胞摄取途径取决于细胞类型和细胞分化。
