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Specks Mark The Clot

Iron oxide nanoparticles functionalized with a fluorescent dye and a peptide light up newly formed clots for diagnostic imaging

by Aaron A. Rowe
June 8, 2009 | A version of this story appeared in Volume 87, Issue 23

Iron oxide nanoparticles, when decorated with a fluorescent dye and the right peptide, can drift through blood vessels and light up newly formed clots to determine whether they are good candidates for treatment with thrombolytic drugs, according to a report by Jason R. McCarthy, Farouc A. Jaffer, and coworkers of Massachusetts General Hospital (Bioconjugate Chem., DOI: 10.1021/bc9001163). Removing those blockages with medication is risky because the same drug that clears one blood vessel may trigger serious bleeding in another area, such as the brain. To avoid those tragic side effects, the researchers proposed that functionalized nanoparticles could serve as magnetic resonance imaging contrast agents to help doctors decide whether a patient should receive clot-busting drugs. Bearing the dye molecules, the same nanoparticles make blockages shine for a catheter-based fluorescence microscope that can be used to watch a treated clot dissolve in real time. Key to the strategy, which the researchers tested in mice, is coupling the particles with a peptide that irreversibly binds factor XIIIa, a protein that is found only in fresh clots. The team plans further studies on the nanoparticles to evaluate thrombolytic drugs in vivo and to monitor clot formation on stents.

Clots in a mouse artery, lit up by nanoparticles that bind fibrin (top) and factor XIIIa (middle). A composite image (bottom) reveals that factor XIIIa is bound throughout, indicating that the bulk of the clot is newly formed.
Credit: Courtesy of Jason McCarthy


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