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January 14th, 2010

Nanodiamond-Gd complex: ‘Contrast agent on steroids’

Published on January 14th, 2010 | By: pwray@ceramics.org

Dean Ho’s nanodiamond team at Northwestern always seems to be coming up with something new. This time, Ho and a team led by NWU cancer researcher Thomas J. Meade say they have figured out a way to couple gadolinium with nanodiamonds to make a MRI contrast agent that delivers greatly improved images.

“The results are a leap and not a small one,” says Meade in a NWU news release “it is a game-changing event for sensitivity. This is an imaging agent on steroids. The complex is far more sensitive than anything else I’ve seen.”

In the past, Ho has shown, at least with in vitro studies, that nanodiamonds seem to have excellent biocompatibility and can be used for drug, protein and DNA delivery. But researchers in that area are looking not only for a system to deliver drugs but also has a second function: tracking. (The ideal drug delivery system adds one more function that allows the material to be targeted to a particular tissue or site.)

In a paper study published online by the journal Nano Letters, the team says they have developed a gadolinium(III)-nanodiamond complex that demonstrated a greater than 10-fold increase in “relaxivity.” Relaxivity refers to ability of magnetic compounds to increase the relaxation rates of the surrounding water proton spins. Relaxivity is used to improve the contrast of the image.

“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 team also studied the toxicity of the Gd(III)-nanodiamond complex using fibroblasts and HeLa cells as biological testbeds, and found that that the material didn’t negatively affect th hybrid complex on cellular viability.

Now the focus is on moving from in vitro to in vivo. The researchers hope to be moving into preclinical application of the new contrast agent in various animal models.

They also think they can fine tune and improve the agent by nailing down how the structure of the Gd(III)-nanodiamond complex governs increased relaxivity.

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