Tethering tiny structures called nanodiamonds to contrast agents used in MR scans could boost their contrast strength ten-fold, scientists discover.

The finding, published in December in the online edition of the journal Nano Letters, means radiologists could get a more vivid signal while using less contrast material, possibly making the procedure safer.

The scientists from Northwestern University in Evanston, Ill. employed nanodiamonds, ultra-tiny, powder-based particles usually some 2 to 8 nanometers in size, or about one-20,000th the width of a single strand of human hair.
These microstructures are "good at stabilizing elements against the surface," Dean Ho, Ph.D., an assistant professor of biomedical engineering at Northwestern University, tells DOTmed News. Dr. Ho, whose lab specializes in nanodiamond research, co-wrote the paper with, among others, Thomas Meade, Ph.D., a chemistry professor at Northwestern and an expert in contrast agents.

When the scientists bound the nanodiamonds to gadolinium-based contrast agents, the resulting conjugate rocketed up the relaxivity, a marker of contrast strength, according to Dr. Ho.

"Basically this agent we've developed allows for more than ten times the efficiency of the relaxivity. It's almost like ten times the signal," Dr. Ho says.

LOWERED DOSE

A stronger signal means less of the injected contrast material, often applied in cardiovascular MR scans, could be used to get the same, or better, imaging results. This is useful because gadolinium-based agents are associated with rare but deadly side effects, and risk increases as the dose goes up.

Lowering the dose also reduces the body's mild inflammatory response to the product, a boon when imaging cancer patients, says Dr. Ho.

"Cancer can in fact benefit from inflammation," he says. "[It] can possibly metastasize towards regions of inflammation. In some cases, inflammation can also block drug activity, the last thing one wants to cancel out."

OTHER MEDICAL APPLICATIONS

Because nanodiamonds appear to be biocompatible, causing little oxidative stress when they rub among cells, they seem born for biological applications.

Two years ago, Dr. Ho's lab used nanodiamonds to help with drug delivery; because the diamond's surface is so good at attaching to proteins, drug ingredients release slowly from it. This is helpful when the drug is somewhat toxic and needs to be administered in small, controlled doses.

And four months ago, Dr. Ho published a paper showing nanodiamonds could help with cutting-edge gene therapy. Usually, gene therapy works by deploying viruses containing modified genes into a host; the virus digs into a cell, and deposits the genes. But Dr. Ho's lab's technique, using nanodiamonds to ferry genes through a cell wall, was 70 times more effective than conventional methods, he says.

Now, the real test, at least for the gadolinium-based conjugate, will be how it holds up in pre-clinical settings. Given that it appears to be safe, Dr. Ho hopes to begin animal studies soon.

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