MRI agent developed for angiogenesis

A magnetic resonance imaging (MRI) contrast agent that targets the growth of new blood vessels has been developed by scientists in the Netherlands. 

MRI is a non-invasive technique used in medicine to look inside the body. Contrast agents, which work by altering the local magnetic field of different tissues, are used to make the images clearer.   

Bert Meijer and colleagues at the Eindhoven University of Technology and the Cardiovascular Research Institute Maastricht have produced a contrast agent that targets angiogenesis, the growth of new blood vessels, after being told by colleagues working in medical research that there wasn’t one available.   

Excessive angiogenesis is a feature of cancer. New blood vessels grow to feed the tumour allowing cancer cells to escape into the bloodstream and travel around the body.   

Target-specific contrast agents must meet two criteria; the contrast agent must accumulate around the regions of angiogenesis, and the sensitivity of the contrast agent must be increased.   

The former was achieved by incorporating a cyclic peptide containing the asparagine-glycine-arginine sequence (cNGR), which is a specific ligand for the aminopeptidase CD13, a protein over-expressed by angiogenic endothelial cells.   

To increase the contrast of the agent, a gadolinum(III) chelate was bound to biotin and four biotins were in turn connected to avidin, a large carrier protein.   

The cNGR was connected to the Gd(III) chelate and the biotin-avidin system to create a target-specific contrast agent capable of accumulating in tissues near angiogenic cells.   

Donald Tomalia, an expert on dendrimer applications at Dendritic Nanotechnologies, Michigan, US, is enthusiastic about the new contrast agent. 

’This brilliant innovation has demonstrated enhanced sensitivity of the MRI agent. The next step will be to demonstrate the in vivo targeting efficacy of these agents, which if successful, portends dramatic progress and possibilities in the earlier stage detection of cancer and other diseases,’ he said.   

Lorna Jack