Ironized Stem Cells Steered By Magnet

Want to direct injected stem cells to certain parts of the body? Try feeding the cells tiny particles of magnetized iron oxide, injecting them intravenously and controlling their movements with a magnet.

W. Robert Taylor, M.D., Ph.D. at Emory University and Gang Bao, Ph.D. of both Georgia Tech and Emory University did just that using mesenchymal stem cells for their study. They noted that these cells are easily obtained from adult tissues, and they secrete a variety of anti-inflammatory factors which could make them valuable tools for treating cardiovascular or autoimmune disorders.

For the iron, they used magnetized iron oxide nanoparticles coated with polyethylene glycol that protects the cell from damage. Previous attempts by scientists to load stem cells with similar particles, found that the coating on the particles was toxic or changed the cells’ properties.

The Emory/Georgia Tech team used a magnetic field to push the particles into the cells, rather than the chemical agents used previously. “We were able to load the cells with a lot of these nanoparticles and we showed clearly that the cells were not harmed, ” Taylor said. “The coating is unique and thus there was no change in viability and we didn’t see any change in the characteristics of the stem cells, such as their capacity to differentiate.

The iron oxide core is about 15 nanometers across, he said, adding that, for comparison, a single influenza virus is at least 100 nanometers wide. The scientists measured the iron content in the cells once they were loaded up and determined that each cell absorbed roughly 1.5 million particles. Once they had loaded the cells with iron oxide particles, the team tested the ability of magnets to nudge the cells in living animals.

A magnet was applied to the tail of a mouse close to its body while the fluorescent dyed cells were being injected. They calculated that the magnet made the stem cells six times more abundant in the tail. They now plan to focus on therapeutic applications in animal models where they will use magnets to direct the cells to the precise site need to affect repair and regeneration of new blood vessels. “Ultimately, we would target these to a particular limb, an abnormal blood vessel or even the heart, ” said Taylor.