title: Quantum dot imaging for embryonic stem cells.
abstract: BACKGROUND
  Semiconductor quantum dots (QDs) hold increasing potential for cellular imaging both in vitro and in vivo. In this report, we aimed to evaluate in vivo multiplex imaging of mouse embryonic stem (ES) cells labeled with Qtracker delivered quantum dots (QDs).
  
  
  RESULTS
  Murine embryonic stem (ES) cells were labeled with six different QDs using Qtracker. ES cell viability, proliferation, and differentiation were not adversely affected by QDs compared with non-labeled control cells (P = NS). Afterward, labeled ES cells were injected subcutaneously onto the backs of athymic nude mice. These labeled ES cells could be imaged with good contrast with one single excitation wavelength. With the same excitation wavelength, the signal intensity, defined as (total signal-background)/exposure time in millisecond was 11 +/- 2 for cells labeled with QD 525, 12 +/- 9 for QD 565, 176 +/- 81 for QD 605, 176 +/- 136 for QD 655, 167 +/- 104 for QD 705, and 1,713 +/- 482 for QD 800. Finally, we have shown that QD 800 offers greater fluorescent intensity than the other QDs tested.
  
  
  CONCLUSIONS
  In summary, this is the first demonstration of in vivo multiplex imaging of mouse ES cells labeled QDs. Upon further improvements, QDs will have a greater potential for tracking stem cells within deep tissues. These results provide a promising tool for imaging stem cell therapy non-invasively in vivo.
authors.affiliation: Molecular Imaging Program at Stanford (MIPS) and Bio-X Program, Department of Radiology, Stanford University, Stanford, CA 94305, USA. susans1018@gmail.com
authors.forename: Shuan
authors.initials: S
authors.lastname: Lin
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Xie
authors.forename: Manishkumar R
authors.initials: MR
authors.lastname: Patel
authors.forename: Yao-Hung
authors.initials: YH
authors.lastname: Yang
authors.forename: Zongjin
authors.initials: Z
authors.lastname: Li
authors.forename: Feng
authors.initials: F
authors.lastname: Cao
authors.forename: Oliver
authors.initials: O
authors.lastname: Gheysens
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Sanjiv S
authors.initials: SS
authors.lastname: Gambhir
authors.forename: Jiang Hong
authors.initials: JH
authors.lastname: Rao
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Wu
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000166:cytology*; D007089:Image Enhancement / Q000379:methods*; D051379:Mice; D008856:Microscopy, Fluorescence / Q000379:methods*; D045663:Quantum Dots