Using a Plant Virus to Create a Contrast Medium

Researchers at the University of Texas Dallas (UTD) are playing with alchemy by transforming a virus into an organic radical contrast agent (ORCA), an alternative to gadolinium-based contrast agents to be used in magnetic resonance imaging (MRI) procedures.

ORCA molecules had been previously considered too dim for scanning and were easily eradicated by vitamin C in the body. UTD researchers found that by connecting the molecules to a tobacco mosaic virus, a virus that attacks plant cells and disrupts cell activity, they were able to eliminate those issues and make the ORCA an effective agent.

Once the ORCA was attached to the virus, the researchers created cucurbiturils, or hollow chemical structures, and wrapped them around every ORCA molecule as a way to protect it from larger molecules and help maintain its luminosity while in the scanner. The cucurbiturils also connects water to the ORCA and virus, which is imperative to generating the MRI image. The researchers used the ORCA on mice and found that the molecules provided over two hours of visible contrast.

"It can't infect people or animals, and it's easily broken down by the liver. Because the virus is so large, it also allows us to put thousands of the ORCA molecules right next to each other," said researcher and Associate Professor of Chemistry and Biochemist.... "It's the difference between having one Christmas tree light, which is pretty dim, and a whole string of them together, which is quite bright."