Seeing in the dark

SEOUL—Noninvasive in vivo imaging methods—such as PET and MRI—are finding increasing use in preclinical studies during drug development, but the techniques are only as good as the contrast agents used to visualize target tissues or cells. Recently, researchers at Yonsei University engineered magnetic nanoparticles to facilitate ultra-sensitive molecular imaging of tumors.

As they reported in Nature Medicine, the researchers used a high-temperature organic-medium-based protocol to generate magnetism-engineered iron oxide (MEIO) nanoparticles. They found that by changing the metal composition—Mn, Fe, Co, or Ni—they could control the magnetic spin of the nanoparticles. The researchers then conjugated the antibody Herceptin to the nanoparticles to facilitate their use in detecting cancer.

In cytotoxicity tests, the researchers determined that the nanoparticles were not detrimental to cell viability. They also noted that the MnMEIO-Herceptin complexes offered the greatest contrast levels when probed against different cancer cell types. They then tested the nanoparticles in vivo and noted that they could easily detect tumors in mice as small as 50 mg, much smaller than those detected by radiotracers.

"Ultimately," the researchers write, "high-performance magnetic nanoprobing systems could play a pivotal role in the real-time visualization of other biological events, such as cell trafficking, cancer metastasis, cellular signaling, and interactions at the molecular and cellular level."