Nanoparticles Traverse Blood-Brain Barrier to Help Improve MRI Visualization

Development of a new brain tumor imaging agent is not an easy task for researchers because such substance has to be not only a good contrast agent, it also has to cross the blood-brain barrier in order to work. Researchers at the University of Washington have now developed fluorescent nanoparticles that can both safely cross the barrier and significantly improve contrast in optical and MRI scans of brain tumors in mice.

Until now, no nanoparticle used for imaging has been able to cross the blood-brain barrier and specifically bind to brain-tumor cells. With current techniques doctors inject dyes into the body and use drugs to temporarily open the blood-brain barrier, risking infection of the brain.
The UW team surmounted this challenge by building a nanoparticle that remains small in wet conditions. The particle was about 33 nanometers in diameter when wet, about a third the size of similar particles used in other parts of the body.
Crossing the blood-brain barrier depends on the size of the particle, its lipid, or fat, content, and the electric charge on the particle. Zhang and colleagues built a particle that can pass through the barrier and reach tumors. To specifically target tumor cells they used chlorotoxin, a small peptide isolated from scorpion venom that many groups, including Zhang’s, are exploring for its tumor-targeting abilities. On the nanoparticle’s surface Zhang placed a small fluorescent molecule for optical imaging, and binding sites that could be used for attaching other molecules.
Future research will evaluate this nanoparticle’s potential for treating tumors, Zhang said. She and colleagues already showed that chlorotoxin combined with nanoparticles dramatically slows tumors’ spread. They will see whether that ability could extend to brain cancer, the most common solid tumor to affect children.

Abstract in Cancer Research: Tumor Paint: A Chlorotoxin:Cy5.5 Bioconjugate for Intraoperative Visualization of Cancer Foci
Press release: Nanoparticles cross blood-brain barrier to enable ‘brain tumor painting’…