T Kevin Hitchens1,
  2, Li Liu3, Virgil Simplaceanu3, 4,
  Lesley M. Foley3, Eric T. Ahrens3, 4, Chien
  Ho3, 4
 1Pittsburgh
  NMR Center for Biomedical Research, Carnegie Mellon University, Pittsburgh ,
  PA, United States; 2Department of Biological Science, Carnegie
  Mellon University, Pittsburgh , PA, United States; 3Pittsburgh NMR
  Center for Biomedical Research, Carnegie Mellon University, Pittsburgh, PA,
  United States; 4Department of Biological Science, Carnegie Mellon
  University, Pittsburgh, PA, United States
Both perfluorocarbon (PFC) and iron-oxide nanoparticles are established reagents for cell labeling and MRI tracking studies. Here we combine these two labels to investigate new applications. We show that 19F MRI can detect PFC-labeled cells in the presence of iron-oxide-labeled cells, opening the possibility of simultaneously tracking two populations of labeled cells. In addition, iron-oxide nanoparticles in the same cell can be used to quench 19F signal from the PFC label. Thus, systemic iron-oxide labeling of macrophages may be used to quench 19F signal taken up from dead PFC-labeled cell transplants, a major limitation to current MRI cell tracking studies.