title: Degradation or excretion of quantum dots in mouse embryonic stem cells.
abstract: BACKGROUND
  Quantum dots (QDs) have been considered as a new and efficient probe for labeling cells non-invasively in vitro and in vivo, but fairly little is known about how QDs are eliminated from cells after labeling. The purpose of this study is to investigate the metabolism of QDs in different type of cells.
  
  
  RESULTS
  Mouse embryonic stem cells (ESCs) and mouse embryonic fibroblasts (MEFs) were labeled with QD 655. QD-labeling was monitored by fluorescence microscopy and flow cytometry for 72 hours. Both types of cells were labeled efficiently, but a quick loss of QD-labeling in ESCs was observed within 48 hours, which was not prevented by inhibiting cell proliferation. Transmission electron microscope analysis showed a dramatic decrease of QD number in vesicles of ESCs at 24 hours post-labeling, suggesting that QDs might be degraded. In addition, supernatants collected from labeled ESCs in culture were used to label cells again, indicating that some QDs were excreted from cells.
  
  
  CONCLUSIONS
  This is the first study to demonstrate that the metabolism of QDs in different type of cells is different. QDs were quickly degraded or excreted from ESCs after labeling.
authors.affiliation: Department of Plastic and Reconstructive Surgery, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, National Tissue Engineering Center of China, Shanghai, China.
authors.forename: Qing Meng
authors.initials: QM
authors.lastname: Pi
authors.forename: Wen Jie
authors.initials: WJ
authors.lastname: Zhang
authors.forename: Guang Dong
authors.initials: GD
authors.lastname: Zhou
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Yilin
authors.initials: Y
authors.lastname: Cao
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D002470:Cell Survival; D053595:Embryonic Stem Cells / Q000378:metabolism*; D005434:Flow Cytometry; D051379:Mice; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D045663:Quantum Dots; D013194:Staining and Labeling
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