Stem cell targeting with magnets

I wish I'd thought of this. A team at Keele University, England, is experimenting with treating stem cells taken from a patient's bone marrow with magnetic nanoparticles. The advantage? They can guide the stem cells exactly where they want them without invasive surgery. Currently, according to this article on the BBC's website, they're using it to grow new bone and cartilage in mice. They're talking five years until they can use it in humans.

Prediction: If this works, it will revolutionize the treatment of brain damage, and there will be very real moral and legal questions about how much of your brain can be replaced with new neurons and leave the essential "you" intact.

Also, I need to check, but I'm pretty sure Masamune Shirow predicted this in the original Ghost in the Shell manga, although as a method to control the implantation of nanomachines, rather than of stem cells.