Delivery of fluorescent probes using iron oxide particles as carriers enables in-vivo labeling of migrating neural precursors for magnetic resonance imaging and optical imaging.

Iron oxide particles are becoming an important contrast agent for magnetic resonance imaging (MRI) cell tracking studies. Simultaneous delivery of fluorescence indicators with the particles to individual cells offers the possibility of correlating optical images and MRI. In this work, it is demonstrated that micron-sized iron oxide particles (MPIOs) can be used as a carrier to deliver fluorescent probes to cells in culture as well as to migrating neural progenitors in vivo. Migrating progenitors were tracked with MRI and easily identified by histology because of the fluorescent probe. These data suggest that using MPIOs to deliver fluorescent probes should make it possible to combine MRI and optical imaging for in vivo cell tracking.