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Lighting up Tumors
Imaging results are often imprecise
because brain cancers are extremely
invasive; © Univ. of Washington
Results showed the nanoparticles improved the contrast in both MRI and optical imaging, which is used during surgery.
"Brain cancers are very invasive, different from the other cancers. They will invade the surrounding tissue and there is no clear boundary between the tumor tissue and the normal brain tissue," said lead author Miqin Zhang, a University of Washington (UW) professor of materials science and engineering.
Being unable to distinguish a boundary complicates the surgery. Severe cognitive problems are a common side effect.
"If we can inject these nanoparticles with infrared dye, they will increase the contrast between the tumor tissue and the normal tissue," Zhang said. "So during the surgery, the surgeons can see the boundary more precisely.
"We call it 'brain tumor illumination or brain tumor painting,'" she said. "The tumor will light up."
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. 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.
MEDICA.de; Source: University of Washington