Researchers use magnetism to target cells to anima...( Scientists have used magnetic fields...)

Scientists have used magnetic fields and tiny iron-bearing particles to drive healthy cells to targeted sites in blood vessels. The research, done in animals, may lead to a new method of delivering cells and genes to repair injured or diseased organs in people.

The study team, led by Robert J. Levy, M.D., the William J. Rashkind Chair of Pediatric Cardiology at The Childrens Hospital of Philadelphia, loaded endothelial cells, flat cells that line the inside of blood vessels, with nanoparticles, tiny spheres nanometers in diameter. The nanoparticles contained iron oxide.

Using an external, uniform magnetic field, Levys team directed the cells into steel stents, small metal scaffolds that had been inserted into the carotid arteries of rats. The uniform magnetic field created magnetic gradients, local regions of high magnetic force that magnetized both the nanoparticles and the stents, thus increasing the attraction between the particles and their target.

The study appears in the Proceedings of the National Academy of Sciences, published online on Jan. 7. Dr. Levys group from Childrens Hospital collaborated with engineers from Drexel University and Duke University.

This is a novel strategy for delivering cells to targets in the body, said Levy, who added that previous researchers have pursued other, less successful approaches to introduce endothelial cells to diseased blood vessels, in the developing medical field of cell therapy.

Levys team created nanoparticles, approximately 290 nanometers across, made of the biodegradable polymer, polylactic acid, and impregnated with iron oxide. (A nanometer is a millionth of a millimeter; in comparison to these nanoparticles, red blood cells are ten to 100 times larger.)

The researchers loaded the nanoparticles into endothelial cells, which had been genetically modified to produce a specific color that could be detected by an imaging system while the animals were a
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