Nanodiamonds - synthetic industrial diamonds only a few nanometers in size - have recently attracted considerable attention because of the potential they offer for the targeted delivery of vaccines and cancer drugs and for other uses. Thus far, options for imaging nanodiamonds have been limited. Now a team of investigators based at the Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital has devised a means of tracking nanodiamonds noninvasively with magnetic resonance imaging (MRI), opening up a host of new applications. They report their findings today in the online journal Nature Communications.

"With this study, we showed we could produce biomedically relevant MR images using nanodiamonds as the source of contrast in the images and that we could switch the contrast on and off at will," says David Waddington, lead author of the paper and a PhD student at the University of Sydney in Australia. Waddington is currently working with Matthew Rosen, PhD, in the Low-Field Imaging Laboratory at the Martinos Center. "With competing strategies, the nanodiamonds must be prepared externally and then injected into the body, where they can only be imaged for a few hours at most. However, as our technique is biocompatible, we can continue imaging for indefinite periods of time. This raises the possibility of tracking the delivery of nanodiamond-drug compounds for a variety of diseases and providing vital information on the efficacy of different treatment options."

Waddington began this work three years ago as part of a Fulbright Scholarship awarded early in his graduate work at the University of Sydney, where he is a member of a team led by study co-author David Reilly, PhD, in the new Sydney Nanoscience Hub - the headquarters of the Australian Institute for Nanoscale Science and Technology, which launched last year. As part of the Reilly group, Waddington played a crucial role in early successes with nanodiamond imaging, including a 2015 paper in Nature Communications. He then sought to extend the potential of the approach by collaborating with Rosen at the Martinos Center and Ronald Walsworth, PhD, at Harvard University, also a co-author of the current study. Rosen's group is a world leader in the area of ultra-low-field magnetic resonance imaging, a technique that proved essential to the development of in vivo nanodiamond imaging.
Previously, the use of nanodiamond imaging in living systems was limited to regions accessible using optical fluorescence techniques. However, most potential diagnostic and therapeutic applications of nanoparticles, including tracking of complex disease processes like cancer, call for the use of MRI - the gold standard for noninvasive, high-contrast, three-dimensional clinical imaging.

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