Iron oxide nanoparticles have shown promise as agents for detecting tumors using magnetic resonance imaging (MRI), but such efforts have been limited by the relatively weak magnetic signal generated by these nanoparticles.
In order to boost this signal, and improve the ability of MRI to detect the smallest tumors, researchers at Yonsei University in Seoul developed a new chemical method for making iron oxide nanoparticles that would enable them to more carefully control the physical and magnetic properties of these particles. As a result of this effort, described in a publication in the journal Nature Medicine, the investigators were able to detect small tumors implanted into mice.
Jinwoo Cheon, Ph.D., who is also a member of Northwestern University’s Nanomaterials for Cancer Diagnostics and Therapeutics Center for Cancer Nanotechnology Excellence, led the team of investigators that explored how various chemical and physical parameters affect the magnetic signal produced by iron oxide nanoparticles. From these studies, the researchers were able to develop a synthetic technique, using high temperatures and organic solvents, that incorporated traces of manganese, cobalt, or nickel into iron oxide nanoparticles of diameters ranging from 6 to 12 nanometers.
Tests on the resulting nanoparticles showed that those containing small amounts of manganese produced a mangetic signal approximately six times stronger than that produced by the iron oxide nanoparticles typically used in MRI studies. The investigators also found that the 12-nanometer-diameter particles generated a magnetic signal that was about 75 percent stronger than the 6-nanometer-diameter particles.
To determine if these manganese-containing iron oxide nanoparticles could better detect cancer cells using MRI, the investigators labeled the nanoparticles with the human cancer-targeting antibody Herceptin. Herceptin, which is used to treat breast cancer, binds to a specific protein, known as HER2/neu that is overexpressed on certain breast and ovarian tumors. For comparison’s sake, the researchers also prepared Herceptin-labeled conventional iron oxide nanoparticles. The researchers then added these labeled nanoparticles to a variety of human cancer cells growing in culture.