Near-Infrared Fluorescence Labeling of Iron Nanoparticles and Applications for Cell Labeling and In Vivo Imaging

In recent years, the near-infrared fluorescence (NIRF) labeled iron nanoparticles were synthesized and applied to labeling human cells for monitoring the engraftment process, imaging tumors, testing intracellular molecular environment surrounding the nanoparticles, and tracing biodistribution of nanoparticles in vivo. These studies demonstrated that the NIRF-labeled iron nanoparticles provided an excellent method not only for cell labeling but also for in vivo monitoring and tracing of iron nanoparticles due to the excellent in vivo imaging performance of the NIR fluorophores. However, the availability of commercial iron nanoparticles labeled with suitable NIRF dyes is limited. Optimal wavelength for in vivo imaging is centered at 800 nm, where tissue autofluorescence is minimal. Here we describe the manufacture of 12-nm 3-dimercaptosuccinic acid-coated Fe₃ O₄ magnetic nanoparticles, their labeling with a new near-infrared fluorophore, IRDye800CW (excitation/emission: 778/806 nm), and their applications for cell labeling and in vivo imaging.