Levy made use of nanotechnologythe application of extremely small materials. His lab team created nanoparticles, approximately 290 nanometers across, made of a biodegradable polymer and impregnated with magnetite, an iron oxide. (A nanometer is one millionth of a millimeter; these nanoparticles are ten to 100 times smaller than red blood cells.). The magnetite in the particles responds strongly to a magnetic field. Being biodegradable, the particles break down safely in the body after releasing their payload.
Levy's team first implanted stainless steel stents into the carotid arteries of live rats. After injecting paclitaxel-loaded nanoparticles into the rat's arteries through a catheter, they produced a uniform magnetic field around each rat for five minutes. The magnetic field, comparable to that produced by existing MRI machines, but one-tenth as strong, magnetized both the stents and the nanoparticles, and drove the particles into the stents and the nearby arterial tissue.
The researchers inserted stents and nanoparticles into a group of control rats, but without using a magnetic field. Five days after receiving the nanoparticle infusion, the magnetically treated animals had four to 10 times as many particles in their stented arteries as the control animals.
Moreover, using magnetic fields to concentrate the treatment had a lasting effect. Fourteen days after using the magnetic field and a single dose of magnetic nanoparticle-encapsulated paclitaxel, the researchers found the rat arteries had significantly lower restenosis than found in arteries of control rats that had no magnetic treatment.
Over the past several years, Levy and colleagues have shown similar proofs of concept in other animal studies, using magnetica
|Contact: John Ascenzi|
Children's Hospital of Philadelphia