Nanodiamonds Significantly Improve Performance of MRI Contrast Agent

Scientists at Northwestern University have been tinkering with nanodiamonds, tiny versions of the common variety that have a regular carbon structure, to discover interesting and practical properties of the material. (See Medgadget’s flashbacks below.) After demonstrating the general biocompatibility of nanodiamonds, the researchers are now learning how to advance these particles into the clinical arena. A new finding, just published in Nano Letters, is paving way for an impressive increase in Gadolinium contrast imaging during MRI procedures. By attaching nanodiamonds to molecules containing Gd, the researchers noted a significantly improved contrast resolution in MRI images.

Ho [Dean Ho, assistant professor of biomedical engineering and mechanical engineering] and Meade [Thomas J. Meade, professor in cancer research] imaged a variety of nanodiamond samples, including nanodiamonds decorated with various concentrations of Gd(III), undecorated nanodiamonds and water. The intense signal of the Gd(III)-nanodiamond complex was brightest when the Gd(III) level was highest.
"Nanodiamonds have been shown to be effective in attracting water molecules to their surface, which can enhance the relaxivity properties of the Gd(III)-nanodiamond complex," said Ho. "This might explain why these complexes are so bright and such good contrast agents."
"The nanodiamonds are utterly unique among nanoparticles," Meade said. "A nanodiamond is like a cargo ship — it gives us a nontoxic platform upon which to put different types of drugs and imaging agents."
The biocompatibility of the Gd(III)-nanodiamond complex underscores its clinical relevance. In addition to confirming the improved signal produced by the hybrid, the researchers conducted toxicity studies using fibroblasts and HeLa cells as biological testbeds.
They found little impact of the hybrid complex on cellular viability, affirming the complex’s inherent safety and positioning it as a clinically significant nanomaterial. (Other nanodiamond imaging methods, such as fluorescent nanodiamond agents, have limited tissue penetration and are more appropriate for histological applications.)
Nanodiamonds are carbon-based materials approximately four to six nanometers in diameter. Each nanodiamond’s surface possesses carboxyl groups that allow a wide spectrum of compounds to be attached to it, not just gadolinium(III).
The researchers are exploring the pre-clinical application of the MRI contrast agent-nanodiamond hybrid in various animal models. With an eye towards optimizing this novel hybrid material, they also are continuing studies of the structure of the Gd(III)-nanodiamond complex to learn how it governs increased relaxivity.

Northwestern press release: Game-changing Nanodiamond Discovery for MRI…
Abstract in Nano Letters: Gd(III)-Nanodiamond Conjugates for MRI Contrast Enhancement
Flashbacks: Nanodiamonds Serve as Transport Mechanism for Therapeutic Insulin; NanoDiamonds…Everyone’s Friend?; Nanofountain Delivers Therapeutic Particles Into Cells