Multifunctional nanoparticle enables new type of biological imaging

July 28, 2010

30-nanometer particle combines a magnetic core with a thin gold shell (Xiaohu Gao, University of Washington)

University of Washington researchers have developed a multifunctional nanoparticle that enables a more precise form of medical imaging.

Nanoparticles are promising contrast agents for ultrasensitive medical imaging. But in all techniques that do not use radioactive tracers, the surrounding tissues tend to overwhelm weak signals, preventing researchers from detecting just one or a few cells.

The new nanoparticle solves this problem by for the first time by combining magnetic properties and photoacoustic imaging to remove background noise. Researchers used a pulsing magnetic field to shake the nanoparticles by their magnetic cores. Then they took a photoacoustic image and used image processing techniques to remove everything except the vibrating pixels.

“We use an external magnetic field to shake the particles,” he explained. “Then there’s only one type of particle that will shake at the frequency of our magnetic field, which is our own particle.”

Experiments with synthetic tissue showed the technique can almost completely suppress a strong background signal.

The 30-nanometer particle consists of an iron-oxide magnetic core with a thin gold shell that surrounds but does not touch the center. The gold shell is used to absorb infrared light, and could also be used for optical imaging, delivering heat therapy, or attaching a biomolecule that would grab on to specific cells.

This could eventually mean that medical assays and cell counts can be done inside the body. In other words, instead of taking a biopsy and inspecting tissue under a microscope, imaging could detect specific proteins or abnormal activity at the source.

More info: University of Washington news