US scientists have developed a method to deliver probes into cells to track the cells. Therapies such as those based on stem cells that require whole body tracking using non-invasive imaging, for example magnetic resonance imaging (MRI), would benefit from the probes.Current nanoparticle-based tracking systems rely on probes entering cells passively, which is inefficient because the probes often get sequestered in endosomes (compartments in cells that sort molecules for degradation or recycling back to the cell membrane). Now, a team from the Lawrence Berkeley National Laboratory led by Brett Helms has avoided this problem by coating a nanocrystal probe with...