It was not your typical CRISPR experiment. The scientists had just injected a mouse’s tail with magnetic nanoparticles bound to an exotic virus containing today’s genome editor of choice. They then plopped the mouse belly-side down atop a block magnet about the size of a deck of cards, positioning it just so. Even with all their attention to detail, however, “we were never sure it would work,” admits bioengineer Gang Bao of Rice University. “We figured, let’s just see what happens.”
What happened was that the magnetic field quickly steered the CRISPR-containing magnetic nanoparticles to the surface of the mouse’s liver cells and kept the particles well away from the heart, lungs, brain, and other organs. The liver is a big target, which makes hitting it the biological version of hitting the proverbial barn door, but the ability to direct CRISPR to a target organ and only a target organ was a big step toward solving one of the toughest challenges for genome editing: precise delivery.