One of the most difficult problem assosiated with stem cell's treatment is to direct them into unhealthy organ. If we just inject them into blood they will stucked in all organs. So if we want to treat a heart, we should direct stem cells into the heart.
However, it was a problem until now. You can not distinguish stem cells from other cells, until you extract them from the ogranism and put into the microscope, of course. Recently scintists from Emory and Georgia Tech discovered a way to direct stem cells using a magnets.
They coated magnetized iron oxide nanoparticle with polyethylene glycol that protects the cell from damage. The particles become stucked into cell's lysosome. After that scientists use a magnet which direct cells to the tail of the mouse. Then procedure was done, they detect the cells at the tail of the animal.
Such method can be a next step which will improve efficiency of stem cell treatment.
Natalia Landázuri, Sheng Tong, Jin Suo, Giji Joseph, Daiana Weiss, Diane J. Sutcliffe, Don P. Giddens, Gang Bao, W. Robert Taylor. Magnetic Targeting of Human Mesenchymal Stem Cells with Internalized Superparamagnetic Iron Oxide Nanoparticles. Small, 2013; DOI: 10.1002/smll.201300570