Targeting diseases with nanotechnology-based therapies supposes precise knowledge of where nanodevices go when released in the human body. Yet current knowledge is anything but precise.
John Frangioni of Beth Israel Deaconess Medical Center in Boston, Massachusetts, Moungi Bawendi of the Massachusetts Institute of Technology in Cambridge and their colleagues went looking for answers in rats. They used near-infrared-emitting semiconductor nanoparticles coated with a polymer of varying lengths to determine how size and hydrophilicity affect where particles end up. Very small particles (around 5.5 nanometres wide) can be excreted by the kidneys, but even smaller ones get trapped in the liver; larger particles seem to target the pancreas, usually difficult to get to because it has few molecular targets. Meanwhile, the largest particles remain in the vasculature for long periods of time.