Enhanced magnetic cell labeling efficiency using –NH2 coated MPIOs

Strategies have been developed for labeling cells with micron sized iron oxide particles (MPIOs) for in vivo visualization of cells by magnetic resonance imaging. Although this approach is well established and has a variety of applications, current protocols employ long labeling times. It has been previously demonstrated that incubation of dextran coated iron oxide nanoparticles with positively charged transfection agents, such as poly‐L‐lysine increases labeling efficiency. Therefore, we sought to ascertain whether preincubating MPIOs with various quantities of poly‐L‐lysine would similarly enhance the rate of magnetic cell labeling. This was also tested against an NH2 functionalized, commercially available MPIO. Indeed, we demonstrate significantly increased rate of magnetic cell labeling with MPIOs previously incubated with varying amounts of poly‐L‐lysine, with robust intracellular labeling at 2 hours. Yet the most robust labeling was achieved with the MPIO‐NH2. Interestingly, even for particle formulations which still had negative zeta potential, enhancement of magnetic cell labeling was achieved. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.